Lower Byersville Creek Flood-Risk Mapping Update - City of ...

EXCELLENCE INENVIRONMENTALCONSULTINGSERVICESXCG File No.: 3-2087-09-01August 11, 2010LOWER BYERSVILLE CREEKFLOOD-RISK MAPPING UPDATEPrepared for:CITY OF PETERBOROUGH500 George Street NorthPeterborough, OntarioK9H 3R9Attention: Mr. Bruno Bianco, P.Eng.Prepared by:XCG CONSULTANTS LTD.2620 Bristol CircleSuite 300Oakville, OntarioL6H 6Z7XCG Consultants Ltd.300-2620 Bristol CircleOakville, ONCanadaL6H 6Z7Tel: (905) 829-8880Fax: (905) 829-8890E-mail:toronto@xcg.com3-2087-09-01/R_3-04108226_Byersville Creek_Mapping Update_FINAL08/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateTABLE OF CONTENTSTABLE OF CONTENTS1. INTRODUCTION.............................................................................................................1-11.1 Background.....................................................................................................1-11.2 Scope of This Report ......................................................................................1-42. STUDY METHOD ...........................................................................................................2-12.1 Information Gathering....................................................................................2-12.1.1 Existing Base Mapping................................................................................ 2-12.1.2 Digital Elevation Model .............................................................................. 2-12.1.3 Photo Evidence of Surface Flooding in 2004 .............................................. 2-12.1.4 Existing Hydraulic Models (HEC-RAS) ...................................................... 2-22.1.5 Lansdowne Place Site Grading ................................................................... 2-22.1.6 Costco Development Site Grading............................................................... 2-32.1.7 Visitors Center Site Grading ....................................................................... 2-32.2 Site Investigations ..........................................................................................2-32.2.1 Survey of Local Residents............................................................................ 2-32.2.2 Ground Survey............................................................................................. 2-42.3 Update of Hydrologic/Flow Routing Model ..................................................2-62.3.1 Background and Approach.......................................................................... 2-62.3.2 Scope of PCSWMM Model Update.............................................................. 2-72.4 Extension of HEC-RAS Models.....................................................................2-82.4.1 Review of Existing HEC-RAS Model ........................................................... 2-82.4.2 Model Extension South of Former CNR Line .............................................. 2-82.4.3 Update to Main Stem Model: CPR Culverts................................................ 2-82.4.4 Integrated Application of the HEC-RAS Models ......................................... 2-93. RESULTS OF ANALYSIS.................................................................................................3-13.1 Model Performance Assessment ....................................................................3-13.1.1 Rainfall Input to Model................................................................................ 3-13.1.2 Model Representation of July 14-15, 2004 Event........................................ 3-13.1.3 Flows Computed By PCSWMM Model........................................................ 3-33.1.4 Mapping of Surface Flooding Using HEC-RAS .......................................... 3-33.2 Regional Storm Event.....................................................................................3-53.2.1 Rainfall Input to Model................................................................................ 3-53.2.2 Flows Computed by PCSWMM Model........................................................ 3-53.2.3 Mapping of Surface Flooding Using HEC-RAS: Existing System............... 3-63.2.4 Mapping of Surface Flooding Using HEC-RAS: Proposed CulvertModifications ............................................................................................................ 3-74. LIMITATIONS OF ANALYSIS..........................................................................................4-14.1 Limitations of Modelling Approach...............................................................4-14.2 Base Mapping.................................................................................................4-15. RECOMMENDATIONS............................................................................................5-15.1 Flood-Risk Mapping Update ..........................................................................5-15.2 Implementation Priorities for Byersville Creek Flood Reduction:.................5-15.3 Additional Recommended Measures..............................................................5-16. REFERENCES CITED .....................................................................................................6-1i3-2087-09-01/R_3-04108226_Byersville Creek_Mapping Update08/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateTABLE OF CONTENTSTABLESTable 2.1Table 3.1HEC-RAS models obtained from ORCA.......................................................2-2Comparison of rainfall of July 14-15, 2004 over Byersville Creekwith Zone 3 Regulatory event .......................................................................3-5FIGURESFigure 1.1 Flood Risk Mapping Updated to 2003 (as supplied by ORCA).....................1-2Figure 1.2 Examiner Ditch...............................................................................................1-2Figure 1.2 Examiner Ditch...............................................................................................1-3Figure 2.1 Pattern of Surface Flooding During July 2004 Event ....................................2-5Figure 3.1 Rainfall of July 14-15, 2004 over Byersville Creek Watershed.....................3-2Figure 3.2 Mapping of Surface Flooding Based on Model Results for July 2004 Event(Modelling "Case 3" - with CNR washouts and 60% blockage at ErskineAvenue pipe inlet) ..........................................................................................3-4Figure 3.3 Mapping of Surface Flooding, Regional Storm: Case 1 - Existing SystemConditions, with no washout at former CNR and no inlet blockage atExaminer Ditch inlet to Erskine Avenue storm sewer ...................................3-9Figure 3.4 Mapping of Surface Flooding, Regional Storm: Case 4 - Same as Case 1,but with the twin 2.0-m culverts under the CPR east of The Parkwayreplaced with a single 1.0-m culvert.............................................................3-10APPENDICESAppendix A Photos of July 2004 event, as Supplied by ORCAAppendix B Hand-out Questionnaire Delivered to Local Residences in February 2010Appendix C Update of PCSWMM Model (Hydrology and Flow Routing)Appendix D HEC-RAS Model Details3-2087-09-01/R_3-04108226_Byersville Creek_Mapping Update08/11/10ii

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateINTRODUCTION1. INTRODUCTIONXCG Consultants Limited (XCG) was retained by the City of Peterborough (City) todevelop an update to flood-risk mapping for the portion of Byersville Creekwatershed that lies south of Lansdowne Street West.1.1 BackgroundFlood-risk mapping for Byersville Creek was first completed in 1991 (Totten SimsHubicki and Marshall Macklin Monaghan, 1991).Updates were carried out in subsequent years, resulting in updated flood-riskmapping completed in 2003.The extent of the flood-risk area mapped as of 2003 is shown on Figure 1.1. Thisfigure was prepared based on a consolidated mapping layer supplied to XCG byOtonabee Region Conservation Authority in 2007.The 1991 mapping and the subsequent updates indicated a flow “spill” from themain channel of Byersville Creek below Lansdowne Street West and east of TheParkway, via twin CSP culverts under the CPR rail line located approximately 160metres east of The Parkway. The spill arrows shown on the 1991 mapping (MapSheet 27B) indicate that the spill flow would travel southward along what is referredto in this report as the “Examiner Ditch” which flows southward past thePeterborough Examiner building at 730 The Kingsway, under the Kingsway andthen to The Queensway and ultimately to the north side of the former CNR line, thenentering into a storm sewer inlet at Erskine Avenue. See Figure 1.2.The 1991 flood-risk mapping and subsequent updates did not delineate the area ofsurface flooding that could result from this spill.In 2009, the Byersville/Harper Creek Flood Reduction Study was completed (seeXCG Consultants report to City of Peterborough, April 27, 2009). This studyexamined flood-reduction alternatives for the watershed as a whole, in response tothe extensive flooding that had occurred during the rainstorm of July 14-15, 2004.The Flood Reduction Study included development of a hydraulic model that allowedfor mapping of potential surface flooding area due to the spill flows along theExaminer Ditch, as far south as the former CNR line (now a recreational pathway).This analysis revealed that the extent of surface flooding during the Regional Stormevent (the “Timmins” event) could be extensive. This was consistent with the factthat the area had reportedly experienced significant surface flooding in the 2004event.Subsequently, flood-risk mapping was prepared for the Examiner Ditch by D.M.Wills Associates. This mapping has been accepted by Otonabee RegionConservation Authority as is currently being used to assist with regulating land usewithin the flood-risk area.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 1-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateINTRODUCTIONFigure 1.1Flood Risk Mapping Updated to 2003 (as supplied by ORCA)3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 1-208/11/10

R AVERSKINE AV!(!(!(!(!(LANSDOWNE!(!(!(!(!(!(!(!(!(!(!(!(!(Figure 1.2Location of Examiner Ditch!(Low Point on RoadwayApprox. 194.6m!(!(Byersville CreekThe Parkway!(!(Pond#CPR Rail Line"Spill" Arrows Indicated on1991 Flood Risk MappingTwin 2.0mCSP culverts"Spill" Arrows Indicated on1991 Flood Risk MappingTHE KINGSWAYExaminer DitchTwin 1.2m culverts#THE QUEENSWAY!(!(!(!(!(!(!(!(!(!(!(!(!( !(BORDEN AVPipe Stub Inlet to Erskine AvenueStorm Sewer (see photo in Appendix C)!(!(!(!(!(CROWN DRKINGSWAY CT!(!(!(!(!(Twin 1.5m culverts!(!(Examiner Ditch!(!(!(!(!(!(!(!(!(CAMERON PLQUEENSWAY CTFORMER CNR LINE (now a paved pathway)!(!(ORPINGTON RDCAMERON ST!(!(!(!(!(!(!(!(!(!(!(

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateINTRODUCTIONA remaining concern is that the mapping presented in the 2009 Flood ReductionStudy may not fully represent the flood-risk potential south of the recreationalpathway, in the area of Mountain Ash Road, Orpington Road, Cameron Street,Erskine Avenue, and vicinity. This area did experience significant surface floodingduring the 2004 event. One concern was that this surface flooding may not havebeen due only to local drainage systems becoming overwhelmed during the 2004event, but that the extent of flooding may have in part been due to surface flowovertop the recreational pathway (former CNR line).1.2 Scope of This ReportAt the City’s request, XCG has undertaken an update to the Regulatory flood-riskmapping for the portion of Byersville Creek that lies south of Lansdowne StreetWest.As described in this report, this update has been based on using availableinformation complemented by some limited additional investigations. The HEC-RAS hydraulic models previously developed for the main stem of Byersville Creekand for the Examiner Ditch have been employed. Additional HEC-RAS modellinghas been carried out to allow for flood-risk mapping south of the recreationalpathway.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 1-408/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHOD2. STUDY METHOD2.1 Information Gathering2.1.1 Existing Base MappingXCG acquired from the City geo-referenced base mapping that includes• Buildings• Roadways, including road curb lines• Additional planimetric features such as watercourses and surface drainagefeatures• Property boundaries (i.e. parcel fabric)Information supplied by the City indicates that the planimetric features mapping wasderived from aerial photography taken in May 2005.The mapping also included topographic contours at 0.25-m elevation intervals, asdeveloped from the City’s digital elevation model (see below).The City also supplied digital aerial photography taken in 2008 by Ontario Ministryof Natural Resources.2.1.2 Digital Elevation ModelXCG also acquired from the City the most recent digital elevation model (DEM).The DEM was developed for the City based on aerial photography taken in 2005.The City advised that the DEM vertical precision is 0.25 metres. Documentationprovided by the City related to the interpretation of the aerial photographs, indicatesthat the raw elevation information from which the DEM was developed has averagevertical elevation error of 0.16 m (per report to City of Peterborough by OSIGeomatics, 2005).The 0.25-m precision of the available topographic mapping is consistent withtechnical guidelines for floodplain mapping that have previously been published bythe Ontario Ministry of Natural Resources ("Flood Plain Management in Ontario:Technical Guidelines" , section "J - Surveys and Mapping Procedures for FloodplainMapping", Ont. Ministry of Natural Resources, 1986).2.1.3 Photo Evidence of Surface Flooding in 2004In 2005, J.W. Merriam & Associates had prepared a report to ORCA providingavailable photographic evidence of surface flooding and high-water elevations thatoccurred in the Byersville Creek watershed during the July 2004 event.For the portion of Byersville Creek watershed of interest, the Merriam report of 2005provide only limited information, indicating that there was surface flooding onErskine Avenue, Crawford Drive and Mountain Ash Road.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHODIn late 2009 and 2010, ORCA staff were able to supply some additionalphotographic evidence of flooding that had occurred on Orpington Road, nearErskine Avenue and The Kingsway, and at the mouth of Byersville Creek. SeeAppendix A.2.1.4 Existing Hydraulic Models (HEC-RAS)The existing HEC-RAS models were acquired from ORCA. The following modelswere acquired:Table 2.1ModelHEC-RAS models obtained from ORCANotes on sourceByersville Creek main stem, fromClonsilla Avenue down to the outlet tothe Otonabee RiverThis is the HEC-RAS model developed from the original 1991 HEC-2 model, with subsequent updates, including final update to 2003 byGreenland Engineering. This 2003 updated model was set up tooperate in HEC-RAS “unsteady mode” to provide dynamic routingof flow hydrographs.Examiner Ditch HEC-RAS model developed by D.M. Wills & Associates in 2009,covering the Examiner ditch from the CPR line down to the ErskineAvenue storm sewer inlet.Examiner Ditch West Spill modelHEC-RAS model developed by D.M. Wills & Associates in 2009 asa complement to the above model. This “side spill” model providesmapping for flooded area due to flow southwestward along the northside of the former CNR line. This flow would result from flow alongthe Examiner Ditch splitting to go two ways, at the 90o bend atwhich the ditch turns to go northeastward to the Erskine Avenuestorm sewer inlet.2.1.5 Lansdowne Place Site GradingThe D.M. Wills flood-risk mapping indicated the potential for the flood-risk area toextend onto the Lansdowne Place property.There has been recent alteration to this property in connection with expanding thecommercial building. XCG was supplied with a paper copy of the site grading anddrainage plan ("Lansdowne Place Re-Development, Site Grading Plan, Project No.04199, Drawing No. SW-G", dated December 2005, prepared by CounterpointEngineering Inc., for 20 VIC Developments Inc.).The digital elevation model supplied by the City does not represent this recentproperty development, since the DEM was developed based on aerial photographytaken in May 2005.Using the site grading plan, XCG has manually digitized and georeferenced anumber of elevation points to represent the current development, and this has beenpatched into the DEM to update the representation of this property parcel in the basemap used to develop the updated flood-risk map.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-208/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHOD2.1.6 Costco Development Site GradingThe digital elevation model supplied to the City also does not reflect the current sitegrading on the recently developed Costco property on The Parkway east of CrawfordDrive.The City supplied XCG with a scanned copy of the this development's site gradingplan (Site grading plan prepared by MMM Group, dated February 13, 2008, Drawingnumber SG1, MMM Project Number 10-03064).As done for Lansdowne Place, XCG has manually digitized and georeferenced anumber of elevation points from this site grading plan, and this has been patched intothe DEM to update the representation of this property parcel in the base map used todevelop the updated flood-risk map.2.1.7 Visitors Center Site GradingThe digital elevation model supplied to the City also does not reflect the current sitegrading on the recently developed Visitors Center/Tim Horton's site locatedimmediately northwest of the intersection of Crawford Drive and The Parkway.The City supplied XCG with a scanned copy of the this development's site gradingplan (Site grading plan prepared by D.M. Wills Associates Limited, dated February11, 2009, Drawing number 1917SS01, D.M. Wills project No. 05-1917), stampedwith City site plan approval dated April 15, 2009.XCG has manually digitized and georeferenced a number of elevation points fromthis site grading plan, and this has been patched into the DEM to update therepresentation of this property parcel in the base map used to develop the updatedflood-risk map.2.2 Site Investigations2.2.1 Survey of Local ResidentsOn February 10, 2010, a hand-out questionnaire was distributed to approximately250 residences along Orpington Road, Cameron Street, Mountain Ash Road, ErskineAvenue, Roger Road and Barnes Crescent. The purpose was to obtain any availableadditional information from residents about where surface flooding occurred andwhere water flowed during the flood event of July 14-15, 2004.Appendix B provides a copy of the questionnaire that was handed out, and a mapshowing where it was distributed.A total of 13 responses were obtained. These provided some useful information. Inparticular, a number of respondents indicated that flow did occur over top of theformer CNR line and that in fact there had been some wash-out of the embankmentin the vicinity of Orpington Road and at the end of Cameron Street.The responses were used to develop a better picture of what happened in the areaduring the July 2004 event.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-308/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHODFigure 2.1 summarizes the information that has been gathered to date regardingwhere surface flooding and surface flow was observed within the watershed area thatlies southeast of the former CNR rail line.Note that Figure 2.1 does not depict all of the surface flooding or surface pondingthat may have occurred during the July 14-15, 2004 event, especially at the peak ofthe event which occurred in the pre-dawn hours of July 15, 2004. Figure 2.1 depictsonly locations and directions of surface flooding that are known, based on directevidence from available photographs and from the recent questionnaire survey oflocal residents (Appendix B) which included a map that allowed respondents to markup locations of observed surface flow and flooding.2.2.2 Ground SurveyBeninger Surveying of Peterborough was retained by XCG to carry out groundsurvey at selected locations that were considered as potentially critical indetermining where surface flows may travel and what depth of flooding might result.The ground survey work was carried out in early March 2010, and included thefollowing:• Centreline elevation profile along the recreational pathway (former CNR line)between Erskine Avenue and Crawford Drive.• Cross-section across the recreational pathway and to the north, in the vicinity ofOrpington Road, to assist with determining flow directions at the 90-degree bendin the Examiner Ditch.• Elevation of culvert under the recreational pathway near northwest corner ofMaster Brand Cabinets industrial building.• Typical road sections and centreline profiles along Orpington Road, CameronStreet, Mountain Ash Road, and Erskine Avenue south of Hawley Street.The survey data were all referenced to the City’s geo-coordinate system.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-408/11/10

WEBBER AVSTMOUNTAIN ASH RDROBERT RDERSKINE AVBARNES CRSURVEY STEDISON AST CATHERINE STFigure 2.1Location of Observed Surface FloodingSouth of Former C.N.R. Line,July 2004 Flood EventFTHE PARKWAY600mm Surface Floodingin Parking LotSurface Floodingof YardKINGSWAY CTCROWN DRTHE KINGSWAYWashout of Rail BedReported to be8 Feet Wide by 4 Feet DeepWashout at Cameron St.Reported to be 30"Below TracksCAMERON PL2 FeetFlow DepthMasterBrandCabinetsQUEENSWAY CT!!EXAMINER DITCH!!!!THE QUEENSWAY!Recreational Pathway (Former CNR Line)!!!Water Depth2.5 to 3 Feetat Centre ofRobert Rd.!CRAWFORD DRBORDEN AV5 Feet of Ponding3 to 4 FeetDepth on RoadLegend!MCKELLAR STGILLESPIE AVORPINGTON RD18 to 20 Inches PondingDepth at IntersectionGrovePublicSchoolCAMERON STBARBARA CRBELLAIRE STCRAWFORD PLDirection of Surface Flow as Reportedby Questionnaire RespondentsRespondents to Questionnaireof February 2010Locations of Overtopping and Washout ofFormer CNR Rail Embankmentfrom Questionnaire RespondentsApproximate Extent of Surface Ponding andRoadway Flooding Based onAvailable Photos & Questionnaire ResponsesSHIRLEY AVHAWLEY STLITTLE STKenner CollegiateVocational InstituteHAROLD PLHAROLD DRMONAGHAN RDSPRUCE AVBRAIDWOOD AVKING GEORGE STNote:This figure does not depict full extent ofsurface flooding, but only the extent andlocations known through available photosor questionnaire responses.HOWDEN STSTEELE AVRIVERSIDE DRARCHIBALD AVROSE AMyersTransport3.5 Feet Flow Depth onCrawford at Robert Rd.!STOCKER RD!BYERSVILLE CREEK0 75 150 3007 & 115 HYFlow From Creekonto Stock Rd.MetresJOHNSTON DR

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHOD2.3 Update of Hydrologic/Flow Routing Model2.3.1 Background and ApproachThrough discussion with the City and ORCA, it was agreed that the technicalanalysis for this project would proceed as follows:1. The hydrologic and dynamic flow-routing components of the PCSWMM2005model developed by XCG for the Byersville/Harper Creek Flood ReductionProject, would be used to develop peak flood flows at various locations.2. The peak flood flows from the PCSWMM2005 model would then be applied in asteady-state HEC-RAS model to develop flood elevation estimates that wouldform the basis for the flood-risk mapping.3. The peak flows that will be given to the HEC-RAS model will come from thePCSWMM2005 model for existing watershed conditions. The hydraulicscomponent of the PCSWMM2005 model computes how much flow leaves themain stem to flow under the CPR line via the twin 2.0-m culverts that are locatedeast of The Parkway.4. Flood flows would be based on simulating the watershed response to theRegional Storm event (the so-called “Timmins” storm) per the current MNRtechnical guidelines for flood-risk mapping (MNR, 2001).5. With respect to representing the effect of stormwater storage ponds, the effects ofsuch structures are not to be included when simulating peak flood flows for usein flood-risk mapping, per the 2002 technical guidelines.The development of the PCSWMM2005 hydrologic and flow-routing model is fullydocumented in the Byersville/Harper Creek Flood Reduction Study report (XCG,2009). In summary, this modelling approach is as follows:1. In using PCSWWM2005, the computational engine was EPA SWMM Version4.4 (Huber at al., 1988).2. For modelling purposes, the watershed was subdivided into 42 constituentsubcatchments based on considering topography and drainage systems.3. Computation of runoff hydrographs from each of these areas was carried outusing the RUNOFF object in PCSWMM2005.4. Addition of these flows and routing through the upper watershed (aboveClonsilla Avenue) was carried out using the TRANSPORT object inPCSWMM2005.5. For the lower portion of the watershed (below Clonsilla Avenue), flows wereadded and routed using the EXTRAN object of PCSWMM2005. The EXTRANobject provides full dynamic routing of flows and accounts for storage effectsassociated with channel or floodplain storage. The EXTRAN object allows for3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-608/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHODrepresentation of backwater effects and of impacts of flood conditions in themain outlet channels on conditions within tributary storm sewer systems.In this approach, the EXTRAN object is providing dynamic routing using the sametechnique that had previously been applied circa 1990 when the NWS DAMBRKmodel had been used to account for floodplain storage effects on the mildly slopedlower portions of Byersville Creek (especially downstream of The Parkway). In themore recent updates to the HEC-RAS model, the newly developed “unsteady flow”capabilities of HEC-RAS had been enabled in the 2003 update (GreenlandEngineering) apparently in an effort to do away with the need for a separate dynamicrouting model.The use of PCSWMM2005 EXTRAN to provide the dynamic flow routing, and thento apply the resulting peak flows in a steady-state version of the HEC-RAS modelhas been selected as the preferred approach, based on discussions with ORCA.2.3.2 Scope of PCSWMM Model UpdateTo support an update to the flood-risk mapping for lower Byersville Creek, it wasdetermined that some modifications to the PCSWWM2005 model were needed.Details are provided in Appendix C. In summary, the modifications were as follows:Modification to Subcatchment BoundariesIt was decided that some minor adjustments to subcatchment boundaries in the lowerwatershed were warranted, to better represent inflow distribution along the mainstem of Byersville Creek, below The Parkway.Also, it was decided that an increase in surface imperviousness was needed in thesubcatchment (Subcatchment 5.1; see Appendix C, Figure C-1, for map) in which issituated the property on which a Costco commercial development has recently beencompleted (in the vicinity of The Parkway and Crawford Drive).Update to Flow Routing ElementsThe PCSWMM2005 EXTRAN model has been modified to include the following(see Appendix C for detail):• Flow routing elements to better represent the possibility of flow spilling over topthe former CNR line (recreational pathway), and resulting surface flow downCameron Street, Mountain Ash Road, Orpington Road and Erskine Avenue.• Potential for lateral split of flow from the Examiner Ditch at the 90-degree bendat the former CNR, with elements added to represent overland flowsouthwestward alongside the recreational pathway; and including the culvert pipeunder the pathway near the northwest corner of Master Brand Cabinets.• Potential for spill flow from the main stem of Byersville Creek flowing eastwardalong Crawford Drive and from Crawford Drive into to drainage swale alongrear yards of homes on Mountain Ash Road.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-708/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHOD• The above routing elements have been added to address the potential floodingpathways as identified from reviewing the available information on whathappened during the event of July 2004.2.4 Extension of HEC-RAS Models2.4.1 Review of Existing HEC-RAS ModelIn order to conduct the analysis of flood levels in the lower area of Byersville Creek,existing HEC-RAS models approved and provided by ORCA were screened andapplied.As noted above, there are three (3) distinct component models that constitute theoverall existing HEC-RAS model within the study area. These three models aresections representing:a. Main branch of Byersville Creekb. Examiner Ditch; andc. Examiner Ditch West Spill alongside former CNR track (recreationalpathway).Each of these models were examined for redundancy (e.g. duplicate cross-sections),consistency with selected base map information and data gaps to facilitate an overallanalysis.Where applicable, existing cross-sections were preserved, with a priority assigned tofield surveyed sections, and new cross-sections were generated as deemed necessary.Additional data was obtained from new survey information (March 2010)commissioned for this project.2.4.2 Model Extension South of Former CNR LineAn additional HEC-RAS model (“Lower Spill” model) has been created to calculateflood levels through the area southeast of the recreational pathway (former CNRline), with flow reaching the main stem of Byersville Creek. The upstream limit ofthis model represents ground surface on southeast side of the recreational pathway,from west of Cameron Street to east of Orpington Road.2.4.3 Update to Main Stem Model: CPR CulvertsThe main stem HEC-RAS model includes representation of the twin CSP culvertsunder the CPR on the main stem of Byersville Creek (west of The Parkway) as twin2.7-m diameter pipes. This reflects what was in place prior to the flood event of July14-15, 2004.During that event, there was reportedly damage to these culverts and some washoutof the rail embankment. The rail company (CPR) carried out an immediatereplacement and repairs, installing a combination of a 3050-mm CSP pipe and a CSP2050-mm pipe.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-808/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateSTUDY METHODThese pipes were subsequently replaced in 2008 by twin 3.6-m diameter CSP pipes,per design prepared for CPR by Hatch Mott MacDonald (HMM Project No. 215529,design drawings dated April 2006).The HEC-RAS model of the main stem has been updated to represent these newculvert pipes. Culvert dimensions and elevations were based on the design drawingprepared by Hatch Mott MacDonald (Plan No. 2155929-C-004, dated April 12,2006).This modified model has been used to analyze the Regional Storm, as reportedbelow.For modelling of the flood conditions that occurred during the event of July 2004,the original model representation of the CPR culverts has been used.2.4.4 Integrated Application of the HEC-RAS ModelsWith the additional of a new component HEC-RAS model, there is the requirementto execute the new model in conjunction with the three existing HEC-RAS models,to compute flood surface elevations for the entire area of interest.The procedure applied was as follows:Step 1Step 2Step 3Step 4Run the Main Stem model in steady-state mode.Run the Lower Spill model (steady state) using starting watersurface elevation from HEC-RAS Section 0+543 of the main stemmodelRun the West Spill model (steady state) using starting watersurface elevation from HEC-RAS Section 1+705 of the main stemmodel.Run the Examiner Ditch model (steady state) using starting watersurface elevation based on higher of the upstream levels from theWest Spill model (HEC-RAS Section 876) or the Lower Spillmodel (HEC-RAS Section 450)Appendix D provides details on the HEC-RAS models, and includes map figureswhich show the section locations.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 2-908/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSIS3. RESULTS OF ANALYSIS3.1 Model Performance AssessmentThe performance of the modelling tools has been assessed by using thePCSWMM2005 model and the HEC-RAS models to compute flows and map outsurface flooding areas for the July 14-15, 2004 event. These results have then beencompared to available information on where surface flooding occurred. Theavailable information on what happened within the study area during the July 2004event has been depicted in Figure 2.1.3.1.1 Rainfall Input to ModelThe rainfall data used to model this event was developed from radar rainfall intensitydata supplied by the City of Peterborough during the Byersville/Harper Creek FloodReduction Study. Total event volume for the July 14-15, 2004 event over theByersville Creek watershed is estimated at 151 mm, which fell over a period of 42hours, between 4:00 am on July 14 and 10:00 pm on July 15, 2004, with the worst ofthe flooding having occurred in the early morning (pre-dawn) of July 15th. SeeFigure 3.1 below, and also Appendix C for further details.3.1.2 Model Representation of July 14-15, 2004 EventInformation from local residents indicates that there was flow overtopping theformer CNR line, and some washout of the low embankment. Refer to Figure 2.1.It appears from the information obtained from local residents that wash-out near thewest end of Cameron Street may have been approximately 2 to 3 metres in width,and approximately 0.5 m in depth. In the vicinity of the west end of OrpingtonRoad, a local resident indicated that there had been flow over the former CNR and awashout approximately 2.4 m wide by 1.2 m in depth.In the PCSWMM EXTRAN model, the wash-out conditions were represented bymodifying the elevation profile of the top of the former CNR line.Another factor that was applied in the EXTRAN model was the potential blockage ofthe storm sewer inlet (stub pipe) to the Erskine Avenue storm sewer, immediatelynorth of the former CNR crossing. Appendix C provides photographs of this inlettaken in 2007, and another taken in 2010. This inlet is obviously prone to debrisaccumulation, and it is considered very likely that at least partial blockage wouldhave occurred during the event of July 14-15, 2004. Accordingly, the model was runfor scenarios in which it was assumed that there was 60% blockage of this inlet.The dimensions of the wash-out at Cameron Street and the degree of blockage of theErskine Avenue storm sewer inlet were considered as potential “calibration”parameters, inasmuch as they could be adjusted to some degree to provide amodelling outcome that reflects what was actually observed during the 2004 event.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSISFigure 3.1Rainfall of July 14-15, 2004 over Byersville Creek Watershed3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-208/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSIS3.1.3 Flows Computed By PCSWMM ModelAppendix C provides a detailed presentation of peak flows computed by thePCSWMM EXTRAN model for the lower Byersville Creek watershed.The peak flows computed by the EXTRAN model for a numerous set of conduitsrepresenting the various flow paths within the area, was resolved into a simplified setof peak flows to be applied in the steady-state HEC-RAS model.Detailed model output tables presented in Appendix D show the flow values appliedwithin the HEC-RAS model.3.1.4 Mapping of Surface Flooding Using HEC-RASFigure 3.2 presents the mapping of estimated surface flooding for the July 14-15,2004, as determined from the water surface elevation computed by the HEC-RASmodel using peak flows from the PCSWMM2005 model.The mapping of the surface flooding areas has been carried out using the DEMsupplied by the City. The general procedure for mapping out the surface floodingareas is as follows:• Water surface elevations computed by HEC-RAS at each cross-section (sectionlocations are shown on the map figure) are considered to be the water surfaceelevation along the full width of the cross-section.• Between each cross-section, the water surface is assumed to be an inclined, flatplane. GIS software tools are used to map out where this plane intersects theground surface defined by the DEM. This intersection is the edge of the surfaceflooding area.• The results are reviewed and adjustments are made in locations where the initialmapping does not appear reasonable when considering topographic contouringand considering whether surface flow from the main path of flow could inactuality spread laterally to all locations indicated on the initial mapping.The PCSWMM EXTRAN surface/overland flowrates presented in Appendix C, andthe resulting mapping of surface flooding as shown on Figure 3.2 demonstrate whatcan be considered as acceptable model performance. The directions and depths ofsurface flow, and the mapping of surface flooding areas appears to be a reasonablyaccurate reflection of what is known to have actually taken place during the 2004event.It should be noted that this favourable result did in part depend on relying on roughestimates of the breadth and depth of the washouts of the former CNR embankmentas reported by local residents, and an assumption that there was 60% blockage of theErskine Avenue storm inlet.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-308/11/10

GOLFVIEW RDWEBBER AVRALPHSON CRWENTWORTH ST1+025 - 190.71ARTHUR AVGOODFELLOW RDWIGHTMAN AVROBERT RD0+725 - 190.38WESTERN AVFORD STERSKINE AV0+543 - 190.36HIGH STMONAGHAN RDKENT STWHITEFIELD DRTHE PARKWAYCLONSILLA AV1+800 - 192.35SILVERDALE RD2+275 - 192.932+031 - 192.682+662 - 195.712+512 - 195.712+332 - 195.702+148 - 192.922+506 - 195.713+025 - 195.761+845 - 192.69RYE ST3+645 - 200.371+346 - 191.453+165 - 196.253+073 - 196.152+917 - 195.732+703 - 195.721+305 - 191.093+554 - 198.791964 - 193.601950 - 193.561+565 - 191.742+961 - 195.742050 - 195.001882 - 193.213+390 - 196.741978 - 194.911800 - 193.041850 - 193.071763 - 193.051700 - 193.041610 - 193.041458 - 192.84CAMERON PL1+527 - 191.532+883 - 195.731+705 - 191.99STORNOWAY PLARTHUR AVCROWN DRTHE KINGSWAY1800QUEENSWAY CTMOUNTAIN ASH RDCHAMBERLAIN PLST MARY'S ST1405 - 192.20THE QUEENSWAY14051327 - 191.990+450 - 191.571250 - 191.790+400 - 191.520+350 - 191.320+300 - 191.160+250 - 191.000+200 - 190.830+150 - 190.630+100 - 190.41BARNES CRSTOCKER RDCHAMBERLAIN STDUFFUS ST0+450 - 191.571777 - 193.05BRUNSWICK AVNEW ROMAINE STBORDEN AVGRADY AV1428 - 192.22BROWN ST0+384 - 190.33BARBARA CRCRAWFORD PLST MARY'S STGILLESPIE AVORPINGTON RDCAMERON STCRAWFORD DR0+223 - 190.29HAWLEY STFRANK STCHAMBERLAIN STBROWN STLUNDY'S LNLITTLE STBELLAIRE STHAROLD DRMERVIN AVNOBLE PLROMAINE STHAROLD PL0+083 - 190.26Cross SectionsLabels0+021 - 186.960+055 - 190.26ALBERT STNew XCG CNRSpill ModelUpdated DMWills ModelUpdated ORCAModelDOUGLAS AVMCCANNAN AVFAGAN AVHOWDEN STSPRUCE AVALFRED STBRAUND PLStation - Water Surface Elevation (m)Water Depth (m)0 - 0.010.01 - 0.050.05 - 0.10.1 - 0.20.2 - 0.30.3 - 0.40.4 - 0.50.5 - 0.60.6 - 0.70.7 - 0.80.8 - 0.90.9 - 11.0 - 1.5PRISCILLA ST1.5 - 22.0 - 2.52.5 - 33.0 - 3.53.5 - 44.0 - 4.54.5 - 5STEELE AVRIVERSIDE DR0+865 - 190.551+187 - 190.897 & 115 HY7 & 115 HYJOHNSTON DRGUTHRIE DRFigure 3.2July 2004 EventSurface FloodingË0 100 200 300 400MetersNote:1. Elevation data is based on the Digital Elevation Model (DEM)provided by the City of Peterborough dated 2005.2. Results are for modelling "Case 3" which includes reportedwashouts of former CNR in vicinity of Orpington Road andCameron Street; and 60% blockage of the Erskine Avenuestorm sewer inlet on the Examiner Ditch.

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSIS3.2 Regional Storm EventOnce model performance had been demonstrated, the Regional Storm event wasanalyzed. As noted above, the analysis was based on applying the updated mainstem HEC-RAS model which represents the twin 3.6-m CSP culverts under the CPRwest of The Parkway as installed in 2008.3.2.1 Rainfall Input to ModelThe Regional Storm for Peterborough is the Zone 3 Regional Storm, as prescribedfor flood-risk mapping by the Ontario Ministry of Natural Resources technicalguidelines (OMNR, 2002). This historical event is also referred to as the“Timmins” event, which is a rain storm that occurred in the Timmins area inSeptember 1961. The Natural Hazard Technical Guidelines (OMNR, 2002) dictatethat this event should be used for flood-risk analysis in the portion of Province inwhich Peterborough is situated.Table 3.2 provided below presents a comparison of the Regional Storm with the July2004 event. Note that the 1-hour and 2-hour durations, the July 2004 event was moreintense. As noted in the 1990 Flood Risk Mapping Study, and also determined bymodelling during the Byersville/Harper Creek Flood Reduction Study (XCG, 2009),this is the range of critical storm duration for the Byersville Creek watershed.Table 3.1Comparison of rainfall of July 14-15, 2004 over ByersvilleCreek with Zone 3 Regulatory eventTable Heading 1July 14-15, 2004 Event OverByersville Creek WatershedRegulatory Timmins StormTotal event 151 mm in 42 hours 193 mm in 12 hrsMaximum amount in 1 hour 46 mm 43 mmMaximum amount in 2 hours 71 mm 63 mmMaximum amount in 6 hours 98 mm 132 mmMaximum amount in 12 hours 118 mm 193 mm3.2.2 Flows Computed by PCSWMM ModelAppendix C provides a detailed presentation of peak flows computed by thePCSWMM EXTRAN model for the lower Byersville Creek watershed, for theRegional Storm.As with the July 2004 event, the detailed PCSWMM EXTRAN flows were resolvedinto a simplified set of peak flows for input to the steady-state HEC-RAS model.Appendix D includes output tables from the HEC-RAS model that list the flowvalues applied in the HEC-RAS model runs.With respect to the twin 3.6-m CSP culverts under the CPR on the main stem ofByersville Creek (west of The Parkway), it should be noted that removing these3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-508/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSISculverts and the rail embankment from the flow routing model would not have anysubstantial effect on peak flows along the main channel of Byersville Creek, sincethere is no significant flow attenuation by the channel storage created by the back-upbehind the rail embankment. This can be seen by reviewing the peak flood flowvalues above and below the CPR rail line as tabulated in Appendix D. On this basis,it was not considered warranted to model the main stem flows with the CPR culvertsremoved or washed out as happened during the July 2004 event. With respect to thecomputation of water surface elevation using HEC-RAS, the effect of the CPRembankment has been included, as required by the OMNR technical guidelines.3.2.3 Mapping of Surface Flooding Using HEC-RAS: Existing SystemFigure 3.3 presents the mapping of estimated surface flooding for the RegionalStorm ("Timmins") event, as determined from the water surface elevation computedby the HEC-RAS model using peak flows from the PCSWMM2005 model.Note that Figure 3.3 is for the existing system without any modifications to existingculverts.As was done for the July 2004 event, the mapping of the surface flooding areas hasbeen carried out using the DEM supplied by the City, with the general procedure asdescribed above.Some points to note about the mapping shown on Figure 3.3.• To map the full spatial extent of flooding, computed water surface elevations ateach modelled cross-section have been projected laterally along the section linesshown on the map figure.• These projections across the DEM did in some areas result initially in surfaceflooding or ponding within isolated patches or pockets that in all likelihoodwould not in fact experience such flooding, because there is no known orapparent hydraulic connection to the floodway. Some judgment and editing wastherefore necessary to develop the mapping as shown.• Similarly, because of the presence of multiple flow paths and the fact that themain stem and Examiner Ditch flow paths go through near 90-degree turns, therewas a requirement for some interpretation and judgment in mapping the floodsurface where cross-sections from the separate HEC-RAS models overlap or areorthogonal to one another.Along the eastern limit of the mapped area, the flood surface from the ExaminerDitch has been projected eastward to Erskine Avenue, and then further eastward ontothe Lansdowne Place property. This reflects a flood surface elevation in the rangeof 192.92 m to 193.02 m along the Examiner Ditch between The Kingsway and TheQueensway, and a low road surface elevation of 192.54 m along a sag in ErskineAvenue just south of The Kingsway. In other words, the mapping of surfaceflooding extending to the east of Erskine Avenue is based on lateral spread of flood3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-608/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSISflow along the Examiner Ditch across Erskine Avenue and then onto the LansdownePlace property.The estimated extent and depth of surface flooding to the east of Erskine Avenue isbased on a revision made by XCG to the City-supplied DEM, whereby elevationinformation taken from the site grading plan for the recent Lansdowne Placeproperty has been patched into the DEM for this property parcel.3.2.4 Mapping of Surface Flooding Using HEC-RAS: Proposed CulvertModificationsThe Byersville/Harper Creek Flood Reduction Study (XCG Consultants, 2009 forCity of Peterborough) provided the City with a number of recommended actions andmeasures to reduce surface flooding throughout the Byersville Creek watershed.One component of the recommended strategy was replacement of the existing twin2.0-m culverts under the CPR east of The Parkway that discharge into the ExaminerDitch; see Figure 1.2 above. The recommendation was that these two culverts bereplaced by a single 1.0-m culvert, to substantially reduce peak flows discharged tothe Examiner Ditch from the area north of the CPR.The effect of this specific measure on downstream flood levels and flooded area hasbeen examined, as modelling scenario "Case 4".To model the effect of this proposed measure, the following procedure was used:• The PCSWMM2005 EXTRAN model was modified to represent the culvertreplacement. It was assumed that culvert invert and length would remain thesame as existing.• The EXTRAN model was then used to simulate system response to the RegionStorm event. It was assumed that there would be no alteration in the naturalponding/storage area situated immediately north of the culverts in question.• The resulting peak flows computed by EXTRAN are provided in map figures inAppendix C of this report. Peak flows entering the Examiner Ditch at the CPRwere reduced from 11.9 m3/s to 5.3 m3/s. Further to the south, the amount ofspill flow over the former CNR is substantially reduced but not completelyeliminated.• The peak flows from EXTRAN were then applied in the HEC-RAS models, andthe resulting flood surface was mapped. Figure 3.4 provides the result.The net effect is a substantial reduction in flooded area between the CPR rail lineand the former CNR line, as well as some reduction within the area south of theformer CNR.With respect to area to the east of Erskine Avenue and particularly the LansdownePlace property and immediate vicinity, there is a substantial benefit and virtual3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-708/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateRESULTS OF ANALYSISelimination of the surface flooding that had been projected under existing conditions(per Figure 3.3). This results from the fact that computed water surface elevationalong the Examiner Ditch between The Kingsway and The Queensway is reduced byapproximately 0.40 metres to a peak elevation of 192.63 m, resulting in watersurface projection eastward that results in 0.10 m of ponding depth overtop ofErskine Avenue at the sag just south of The Kingsway intersection, and projectionfurther to the east as shown on Figure 3.4.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 3-808/11/10

WEBBER AVRALPHSON CRWENTWORTH ST1+025 - 190.71ARTHUR AVWIGHTMAN AVROBERT RD0+725 - 190.41WESTERN AVFORD STERSKINE AV0+543 - 190.41HIGH STMONAGHAN RDKENT STWHITEFIELD DRTHE PARKWAYCLONSILLA AV1+800 - 192.332+275 - 192.922+031 - 192.672+662 - 195.722+512 - 195.712+332 - 195.72+148 - 192.912+506 - 195.713+025 - 195.751+845 - 192.66RYE ST3+645 - 200.381+346 - 191.443+165 - 196.243+073 - 196.152+917 - 195.732+703 - 195.72Costco1+305 - 191.083+554 - 198.781964 - 193.581950 - 193.541+565 - 191.732+961 - 195.732050 - 194.881882 - 193.193+390 - 196.721978 - 194.791800 - 193.011850 - 193.041763 - 193.021700 - 193.021610 - 193.011458 - 192.84CAMERON PL1+527 - 191.522+883 - 195.731+705 - 191.98STORNOWAY PLARTHUR AVCROWN DRTHE KINGSWAY1800QUEENSWAY CTST MARY'S STMOUNTAIN ASH RDCHAMBERLAIN PL1405 - 192.15THE QUEENSWAY14051327 - 191.950+450 - 191.291250 - 191.770+400 - 191.220+350 - 191.050+300 - 191.040+250 - 190.910+200 - 190.710+150 - 190.560+100 - 190.37BARNES CRSTOCKER RDCHAMBERLAIN STDUFFUS STNEW ROMAINE STBORDEN AV0+450 - 191.291777 - 193.021428 - 192.18HAWLEY STGRADY AVBROWN ST0+384 - 190.41BARBARA CRLansdownePlace"Lansdowne Place siteplan indicates emergencyspillway elevation of 192.40m.CRAWFORD PLROMAINE STST MARY'S STGILLESPIE AVORPINGTON RDCAMERON STCRAWFORD DR0+223 - 190.41FRANK STCHAMBERLAIN STBROWN STLUNDY'S LNLITTLE STBELLAIRE STHAROLD DRMERVIN AVNOBLE PLHAROLD PL0+083 - 190.410+021 - 190.410+055 - 190.41ALBERT STCross SectionsLabelsDOUGLAS AVMCCANNAN AVFAGAN AVHOWDEN STSPRUCE AVALFRED STNew XCG CNRSpill ModelUpdated DMWills ModelUpdated ORCAModelBRAUND PLStation - Water Surface Elevation (m)Water Depth (m)0 - 0.010.01 - 0.050.05 - 0.10.1 - 0.20.2 - 0.30.3 - 0.40.4 - 0.50.5 - 0.60.6 - 0.70.7 - 0.80.8 - 0.90.9 - 1PRISCILLA ST1.0 - 1.51.5 - 22.0 - 2.52.5 - 33.0 - 3.53.5 - 44.0 - 4.54.5 - 5Current RegulatoryFlood Risk Lineper ORCASTEELE AVRIVERSIDE DR0+865 - 190.561+187 - 190.897 & 115 HYJOHNSTON DR7 & 115 HYGUTHRIE DRMCNAMARA RDFigure 3.3Regional Storm EventExisting Condition (Modelling Case 1)Surface FloodingË0 100 200 300 400MetersNote:1. Elevation data used in the analysis is based on the Digital Elevation Model(DEM) provided by the City of Peterborough dated 2005. All ground elevationsare based on the DEM with the exception of the Costco and Lansdowne Placeproperties which have been developed since then. Site grading plans for the twoproperties were used to modify the DEM to more accurately represent thedevelopments. Site grading plan for Costco property by MMM Group, datedFeb.13, 2008. Site grading plan for Lansdowne Place by CounterpointEngineering dated June 4, 2008.2. The potential extent of surface flooding associated with any spill via theLansdowne Place emergency spillway has not been analyzed.

GOLFVIEW RDWEBBER AVRALPHSON CRWENTWORTH ST1+025 - 190.71ARTHUR AVGOODFELLOW RDWIGHTMAN AVROBERT RD0+725 - 190.41WESTERN AVFORD STERSKINE AV0+543 - 190.410+543 - 190.410+384 - 190.41HIGH STSHIRLEY AVMONAGHAN RDKENT STWHITEFIELD DRTHE PARKWAYCLONSILLA AV2+031 - 192.671+800 - 192.332+332 - 195.72+148 - 192.911+565 - 191.73SILVERDALE RD2+275 - 192.922+031 - 192.672+662 - 195.252+512 - 195.242+332 - 195.222+148 - 192.911+845 - 192.66RYE ST2+506 - 195.231+800 - 192.333+025 - 195.482+917 - 195.731+845 - 192.663+645 - 200.382+961 - 195.732+883 - 195.732+662 - 195.722+275 - 192.922+512 - 195.713+390 - 196.721+346 - 191.443+165 - 196.243+073 - 196.152+917 - 195.33+554 - 198.78 3+554 - 198.782+703 - 195.72Costco1+305 - 191.081964 - 193.511+565 - 191.731+187 - 190.891950 - 193.333+390 - 196.722+961 - 195.321882 - 192.82050 - 1962+703 - 195.261978 - 1961800 - 192.751850 - 192.781763 - 192.631700 - 192.611610 - 192.531458 - 192.351+705 - 191.981+346 - 191.443+165 - 196.243+073 - 196.153+025 - 195.75CAMERON PL1+527 - 191.522+883 - 195.291+705 - 191.98STORNOWAY PLARTHUR AVCROWN DRTHE KINGSWAY1+527 - 191.527 & 115 HY0+865 - 190.561800QUEENSWAY CTMOUNTAIN ASH RDCHAMBERLAIN PLST MARY'S ST1405 - 192.15THE QUEENSWAY14051327 - 192.090+450 - 191.241250 - 192.050+400 - 191.150+350 - 191.020+300 - 190.960+250 - 190.870+200 - 190.620+150 - 190.460+100 - 190.37BARNES CRSTOCKER RDCHAMBERLAIN STDUFFUS ST0+450 - 191.241777 - 192.74BRUNSWICK AVNEW ROMAINE STBORDEN AVGRADY AV1428 - 192.16BROWN ST0+384 - 190.41CRAWFORD PLLansdownePlaceGILLESPIE AVORPINGTON RDBARBARA CRST MARY'S STCAMERON STCRAWFORD DR0+223 - 190.410+223 - 190.41HAWLEY STFRANK STCHAMBERLAIN STBROWN STLUNDY'S LNLITTLE STMERVIN AVBELLAIRE STHAROLD DRNOBLE PLROMAINE ST0+055 - 190.410+083 - 190.41Cross SectionsLabels0+083 - 190.410+021 - 190.410+055 - 190.41ALBERT STNew XCG CNRSpill ModelUpdated DMWills ModelUpdated ORCAModelDOUGLAS AVMCCANNAN AVFAGAN AVHOWDEN STSPRUCE AVALFRED STBRAUND PLStation - Water Surface Elevation (m)Water Depth (m)0 - 0.010.01 - 0.050.05 - 0.10.1 - 0.20.2 - 0.30.3 - 0.40.4 - 0.50.5 - 0.60.6 - 0.70.7 - 0.80.8 - 0.90.9 - 11.0 - 1.51.5 - 22.0 - 2.52.5 - 33.0 - 3.53.5 - 44.0 - 4.54.5 - 5PRISCILLA STCurrent RegulatoryFlood Risk Lineper ORCASTEELE AVRIVERSIDE DR7 & 115 HYJOHNSTON DRGUTHRIE DRFigure 3.4Regional Storm Event with ProposedCPR Culvert Replacement (ModellingCase 4) Surface FloodingË0 100 200 300 400MetersNote:1. Elevation data used in the analysis is based on the Digital Elevation Model(DEM) provided by the City of Peterborough dated 2005. All ground elevationsare based on the DEM with the exception of the Costco and Lansdowne Placeproperties which have been developed since then. Site grading plans for the twoproperties were used to modify the DEM to more accurately represent thedevelopments. Site grading plan for Costco property by MMM Group, datedFeb.13, 2008. Site grading plan for Lansdowne Place by CounterpointEngineering dated June 4, 2008.

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateLIMITATIONS OF ANALYSIS4. LIMITATIONS OF ANALYSIS4.1 Limitations of Modelling ApproachAs described above, the modelling approach has been based on the use of EXTRANfor dynamic flow routing and computation of how much flow travels along variousflow paths within the subject area. HEC-RAS has then been used in “steady state”mode to compute water surface elevations associated with the peak flows computedby EXTRAN.This approach accounts for the considerable surface storage effects that are presentwithin the subject area, along the main stem of Byersville Creek itself, and withinother area subject to surface ponding or flooding. Additionally, this approachaccounts for capacity limitations of the storm sewer system and represents the factthat surcharging of pipe systems such as the Erskine Avenue storm sewer may havecontributed to surface flow along streets such as Erskine Avenue.The modelling approach is considered to be a reasonable representation of thesystem, considering the favourable reproduction of what occurred during the eventof July 2004. However, it needs to be recognized that the modelling tools that havebeen applied are what is termed “one dimensional” models of open channel flow.The models have been applied such that a number of interconnected flow conduitshave been used to provide a presentation of what is in fact a very two-dimensionalsituation in which surface flow does not follow one well-defined floodway, butinstead bifurcates, flows along multiple surface paths, and then reconverges near thewatershed outlet.While the modelling approach is considered a reasonable approximation, it needs tobe realized that it may not account for all localized flow patterns. Nonetheless, theresulting mapping of the area subject to surface flooding is considered to be acomprehensive mapping of where flooding risk exists, based on the availabletopographic base mapping.4.2 Base MappingThe topographic base mapping and the resulting mapping of flooded areas, is derivedfrom the digital elevation model (DEM) supplied by the City. The vertical precisionof the DEM is 0.25 m, having been reportedly derived from air photo interpretationin which a vertical accuracy of 0.16 m was achieved (per report to City ofPeterborough by OSI Geomatics, 2005).As noted above, the 0.25-m precision of the available topographic mapping isconsistent with technical guidelines for floodplain mapping that have previouslybeen published by the Ontario Ministry of Natural Resources ("Flood PlainManagement in Ontario: Technical Guidelines" , section "J - Surveys and MappingProcedures for Floodplain Mapping", Ont. Ministry of Natural Resources, 1986).3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 4-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateLIMITATIONS OF ANALYSISThe original DEM supplied by the City, having been based on aerial photographytaken in May 2005, did not reflect recent site developments on the Costco property(circa 2008) on The Parkway east of Crawford Drive, or the recent redevelopment ofLansdowne Place (circa 2009). Site grading plans for these two propertydevelopment has been used to update the DEM for these two specific properties bymanually digitizing sufficient elevation points to provide mapping precision (i.e.density of elevation points) over those two properties that meets or exceeds that ofthe original DEM coverage of those properties.On this basis, the mapping provided in this report represents mapping of surfaceflooding area that is based on best available information, and which therefore can beused as the basis for finalising an update to the flood-risk mapping for this area.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 4-208/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateFINALIZATION OF MAPPING5. RECOMMENDATIONS5.1 Flood-Risk Mapping UpdateIt is recommended that the flood mapping presented in this report (Figure 3.3) beconsidered by the City of Peterborough and Otonabee Region ConservationAuthority, as an update to the Regulatory flood-risk mapping within the ByersvilleCreek watershed below Lansdowne Street West. This would fulfill therecommendation made in the Byersville/Harper Creek Flood Reduction Study (April2009) that the flood-risk mapping in the area should be updated.5.2 Implementation Priorities for Byersville Creek Flood Reduction:With respect to the replacement of the existing twin 2.0-m CSP culverts locatedunder the CPR line east of The Parkway as recommended in the Byersville/HarperCreek Flood Reduction Study report, the analysis presented here has confirmed thatthis individual modification will have immediate benefits in the lower watershed.This analysis has confirmed that his measure should be considered a high priority interms of implementing the various measures recommended in the Byersville/HarperCreek Flood Reduction Study. The Byersville/Harper Creek Study report (Table6.2) recommended that this culvert replacement be considered a top priority giventhat it, along with other measures recommended for the lower watershed, wouldprovide a benefit/cost ratio of approximately 4.2. This recommendation thereforeremains appropriate.The Byersville/Harper Creek Flood Reduction Study report provides an estimatedcost for the culvert replacement of $300,000.5.3 Additional Recommended MeasuresThe Byersville/Harper Creek Flood Reduction Study recommended that culvert inlettrash racks be improved at a number of locations within the watershed.Improvements to various culvert inlet trash racks were identified as a priority forimplementation of the overall flood-reduction strategy.The inlet trash rack on the Examiner Ditch at the pipe inlet to the Erskine Avenuestorm sewer (see Figure 1.2) should be included amongst these priority locations.Routine inspection and clean-out of any accumulated debris along the ExaminerDitch should be part of routine storm drainage system maintenance carried out by theCity.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 5-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateREFERENCES CITED6. REFERENCES CITEDGreenland International Consulting, 2003. Byersville Creek Two-Zone conceptAssessment for Floodplain Planning & Encroachment Analysis Study Report.Prepared for City of Peterborough. Sept. 2003.Huber, W.C. and R.E. Dickinson (1988), Storm Water Management Model User'sManual, Version 4, EPA/600/3-88/001a (NTIS PB88-236641/AS),Environmental Protection Agency, Athens, GA, 1988, 595 pp.John W. Merriam & Associates, 2005. High Water Mark Descriptions, PeterboroughFlood of July 15, 2004. Prepared for Otonabee Conservation, dated May2005.Marshall Macklin Monaghan Limited and Totten Sims Hubicki Limited, 1991.Flood Risk Map Sheets for Otonabee River Tributary - Byersville Creek.Prepared as part of Canada-Ontario Flood Damage Reduction Program. Mapnumbers OTR4-26, 4-27A, 4-27B, 4-28, 4-29 and 4-30. Dated March 1991(OTR4-26 updated Nov 1995 from CNR to CPR).Ontario Ministry of Natural Resources, 2002. “Technical Guide – River and StreamSystems: Flooding Hazard Limit”, prepared by Ont. Ministry of NaturalResources Water Resources Section, 300 Water Street, P.O. Box 7000,Peterborough, Ontario. Published as part of Ontario’s Natural HazardsTechnical Guidelines, prepared by the Ontario Ministry of Natural Resourcesin support of the natural hazards policies 3.1 of the Provincial PolicyStatement of the Province of Ontario’s Planning Act. © 2001, Queen’sPrinter for Ontario. Published by Watershed Science Centre, TrentUniversity, Peterborough, Ontario, Canada. ISBN 0-7794-1008-4.OSI Geomatics, 2005. "Aerial Triangulation Report for City of Peterborough",prepared by OSI Geomatics, 107 - 930 West 1st Street, North Vancouver,B.C. V7P 3N4. OSI project # 050099, report dated June 29, 2005.Roesner, L.A., Aldrich, J.A. and R.E. Dickinson (1988), Storm Water ManagementModel User's Manual, Version 4: Addendum I, EXTRAN, EPA/600/3-88/001b (NTIS PB88236658/AS), Environmental Protection Agency,Athens, GA, 1988, 203 pp.Totten Sims Hubicki Associates, 1990. “Flood Risk Mapping Study”, prepared forCity of Peterborough and Otonabee River Conservation Authority underCanada/Ontario Flood Damage Reduction Program; “Volume 2 Hydrology”dated Feb. 9, 1989 and “Volume 3 Hydraulics Report” dated Dec. 1990.XCG Consultants, 2009. Byersville/Harper Creek Flood Reduction Study FinalReport, including technical appendices. Report prepared for City ofPeterborough Utility Services Department, attention Mr. Chris Lang., P.Eng.,report dated April 27, 2009.3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update 6-108/11/10

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateAPPENDICESAPPENDIX APHOTOS OF JULY 2004 EVENTAS SUPPLIED BY ORCA3-2087-09-01/R_3-04108226_Byersville Creek Mapping Update08/11/10A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownLooking east along Orpington Road at Erskine Ave intersectionLooking southward from north side of Orpington at a location roughly mid-way between CNR and ErskineXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 1 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownLooking eastward along Orpington, per Google street viewSame location as aboveXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 2 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownAlong Orpington RoadAlong Orpington RoadXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 3 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownAlong Orpington RoadThe Parkway at Queensway (looking northward through the intersection)XCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 4 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownCrawford Drive facing east from Myers TruckingCrawford Drive facing west at entrance to Myers TruckingXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 5 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownLooking north from The Kingsway, just west of Erskine AvenueLansdowne PlaceXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 6 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownLansdowne PlaceLooking westward along Lansdowne Street at The Parkway intersectionXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 7 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownJohnston Drive outlet to Otonabee RiverLooking at downstream face of Con-Span culvert under Johnston Rd (flow into Otonabee River)XCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 8 of 9APPENDIX A

APPENDIX A: PHOTOS PROVIDED TO XCG BY ORCA IN LATE 2009 AND EARLY 2010Photos taken July 15, 2009, Exact time of day of these photos is unknownSubmerged inlet of Johnston Road culvertLooking upstream at Byersville Creek, from Johnston RoadXCG file 3-2087-09-01 Lower Byersville Creek Flood Risk Mapping Report Page 9 of 9APPENDIX A

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateAPPENDICESAPPENDIX BHAND-OUT QUESTIONNAIRE DELIVERED TOLOCAL RESIDENCES IN FEBRUARY 20103-2087-09-01/R_3-04108226_Byersville Creek Mapping Update08/11/10B

APPENDIX BHAND-OUT QUESTIONNAIRE DELIVERED TO LOCAL RESIDENCESFEBRUARY 2010In February 2010, XCG Consultants prepared and distributed a questionnaire to local residentswithin the residential area south of the former CNR rail line. The purpose of the questionnairewas to gather further information on the flood event of July 14-15, 2004, particularly withrespect to where surface flow and surface flooding had happened in the area.The following items are included in this appendix:1. A copy of the questionnaire (3 pages including map, see below) that was handed outdoor-to-door within the area. Distribution took place on February 10, 2010.2. A map showing where the questionnaire was distributed. A total of 250 copies of thequestionnaire were distributed.3. A table summarizing the comments and information received. A total of 13 responseswere received, one by e-mail and the remainder by regular post.4. As noted in the table, a few photos were submitted with some of the responses. Thesephotos are also included here.XCG file 3-2087-09-01 APPENDIX B Page 1 of 9Residents Survey Questionnaire

February 9, 2010Dear Resident,XCG Consultants Ltd. (an engineering consulting firm) has been retained by the City ofPeterborough’s Utility Services Department to update the flood-risk map for Byersville Creek.The flood-risk map identifies areas that may be subject to risk of surface flooding during a rarerainfall event known as the Regional Storm. For Peterborough, the Regional Storm is anhistorical rain event known as the “Timmins” storm that occurred in 1961. This rainfall waslarger than rainfall that caused extensive flooding in Peterborough on July 14-15, 2004.To assist with the update, XCG wishes to obtain information from residents in your area aboutthe extent of surface flooding and runoff flow during the event of July 14-15, 2004. Currently,we have some photos from July 15, 2004, obtained from the Otonabee Region ConservationAuthority and the City of Peterborough, showing surface flooding along Erskine Avenue, alongCrawford Drive and along Orpington Road.We wish to obtain any additional photos or recollections you may have regarding the July 2004flood. Information we are interested in includes depth of flood water, duration of flooding, anddirection of flow. One particular question we have is: Did water flow southward over top ofwhat is now the recreational pathway (former CNR rail line) and flow on to Orpington Road, orCameron Street or Mountain Ash Road?Please see the attached map. You can sketch on it any information you have about where thewater flowed, and where flooding happened, and then mail it back to us, along with anycomments or photos you may have. Or you can e-mail to us if you like. Please see our addressbelow.We appreciate any information you can provide. The information will be used to help verify thatour flood mapping is accurate.Yours truly,Harold Chard, P.Eng.,XCG Consultants Litd.,2620 Bristol Circle,Oakville, Ontario L6H 6Z7E-mail: haroldc@xcg.comPhone : 905-829-8880 x239XCG file 3-2087-09-01 PAGE 1 of 3

XCG file 3-2087-09-01 PAGE 2 of 3

MOUNTAIN ASH RDBARNES CRROBERT RDERSKINE AVTHE QUECROWN DRMCKELLAR STEXAMINER DITCHKAWARTHA BATTERY671 ERSKINE AVEGILLESPIE AVQUEENSWAY CTKENNER COLLEGIATEVOCATIONAL INSTITUTERECREATIONAL PATHWAY (FORMER CNR LINE)CAMERONST PARKORPINGTON RDCAMERON STFGROVE PUBLICSCHOOLBELLAIRE STMASTERBRANDCABINETSBARBARA CRCRAWFORD PLCRAWFORD DRSTOCKER RDBYERSVILLE CREEK0 25 50 100 150 200Meters

MAP SHOWING EXTENT OF HAND-OUT DISTRIBUTION OF THE QUESTIONNAIREXCG file 3-2087-09-01 APPENDIX B Page 5 of 9Residents Survey Questionnaire

ResponseNo.XCG file 3‐2087‐09‐01Project TitleLower Byersville Creek Flood‐risk Mapping UpdateClientCity of Peterborough, Mr. Bruno Bianco, P.Eng.SubjectResidents' Survey ResponsesAs of April 14, 2010Name Address Flooding Type Flooding Location Measurements Photos/Sketch Comments1 Myles& Valerie Harrison Orpington Rd. Surface Orpington Rd. from CNR Line 4ft (1.22m) depth on the street SketchExtend‐ Approx. 3ft (0.91m) from doorstep2 Barnes Cr. Surface Barnes Cr. To Erskine Ave. "knee" high / could be 2‐3ft3 Mountain Ash Rd. Basement FloodingBack of the properties on the west side ofMountain Ash 2.5 ft of water in the basement Sketch4 Photos‐ View fromLaneway eastNo basement floodingDepth & Horizontal distance can be estimated / No basement floodingNot clear if water entered through windows and/or garage door, or sewer backup. Noinformation on depth of surface flooding. Sketch indicates flow north towards Cameron St ‐local grading behind the buildings?SurfaceBack of the properties on the west side ofMountain AshSketchNo flooding at North end of Mountain Ash, surface flooding at the south end. Indicatesflood from the main Creek/backwater, as well, as flow from the west along Cameron St.Mountain Ash & Crawford Dr.Water drained‐off approx. 30 min after rain stopped.4 835 Mountain Ash Rd.5 Cameron St./East of ErskineSurface & BasementFlooding, incl. SewageWashout at CNR Tracks & Cameron St 12 inches of water on Cameron St Berm wash‐out under the tracks Cameron St & CNR (Pathway)Water coming along Erskine Ave. in northdirection from Crawford Dr. and overflowingonto Cameron St. 6‐7inch of water in the basement Indicates potential backwater from main creek,Water from west side of Cameron contributedto the flooding as well.West side of Cameron is lower than east part.6 Cliff & Carol Block 858 Cameron St. Surface Washout at CNR Tracks & Examiner Ditch SketchOrpington Rd, Cameron St, Mountain Ash &Rear yard swaleApprox. within 15ft front and back of thepropertyNo basement flooding/property slightly higher than adjacent properties7 Robert Rd. Surface Crawford Dr. & Robert Rd. 3.5 ft depth on Crawford Dr. Sketch Approx. a couple of hrs before water levels subsided.8 Stocker Rd. Surface Stocker Rd Sketch Water from main creek9 845 Stocker Rd. Surface Stocker RdWater from main creek came up to 3m 2 photos of maininto the back yard. Front yard ‐ water level creek, 1 photo ofpast the tree.street floodingPhotos taken when water was already receding. No indication of overflow on Stocker Rdfrom main creek. Mostly street flooding.10 Linda & William Theobald 814 Orpington Rd. Surface Washout at CNR Tracks & Examiner DitchBreach approx. 8 ft wide and 4 ft deep andapprox. 5ft flood depth in the field behindthe property. Approx. 3ft of water onOrpington St. Sketch/2 Photos Channel still is full of debris.Overflow/Washout at CNR Tracks atintersection with Cameron St & Orpington RdSketch11 525 Robert Rd. Surface Robert RdWater approx. within 15 ft of Robert Rdonto the front yard. Sketch Indicated overflow/flow direction from Crwaford Dr. North.12 507 Robert Rd.Surface & basementflooding.Robert Rd13 Ron Geeza 835 Cameron St., Apt. 4 Surface Cameron StWater levels on the street were approx.2.5 to 3 ft deep at the C/L. Most homesreceived approx.1ft to 16 inch. of water intheir basementsCNR berm washout‐ approx. 30 inch depthbelow the tracks. Approx. 18‐20 inches ofdepth at the intersection of Cameron andErskine Ave. The water did not crestMonaghan St.e‐mailFlows from Crawford Dr. Manholes along the street were lifted. Grading at the back of theproperties has been altered by the property owners over the years resulting in ineffectivedrainage even during small storm events. (drainage also includes small drainage pipes).First sign of sewer backup observed at about 5:30am. Within 90 minutes water reachedapprox. 16 inch depth (peak WL)Berm wash‐out under the tracks Cameron St & CNR (Pathway). Approximately 20yards ofmaterial removed by water from under the tracks. At the outlet to Otonabee River, approx.40 ft of water jet from the culvert into the river.

PHOTOS THAT ACCOMPANIED SURVEY RESPONSES:Surface flooding on BarnesCrescent, at north intersectionwith Erskine Ave. In the bottomphoto, the pickup truck issouthbound on Erskine. Publicschool is in the background.XCG file 3-2087-09-01 APPENDIX B Page 7 of 9Residents Survey Questionnaire

XCG file 3-2087-09-01 APPENDIX B Page 8 of 9Residents Survey QuestionnaireWater level in main channel ofByersville Creek immediatelysouth of Stocker Road, sometime after the peak of the eventof July 2004.

Surface flooding on Stocker Road (south west corner). Resident reported that mainsource of water was from the Byersville Creek channel (flow between the houses)XCG file 3-2087-09-01 APPENDIX B Page 9 of 9Residents Survey Questionnaire

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateAPPENDICESAPPENDIX CUPDATE OF PCSWMM MODEL(HYDROLOGY AND FLOW ROUTING)3-2087-09-01/R_3-04108226_Byersville Creek_Mapping Update04/16/10C

APPENDIX CUPDATE OF PCSWMM MODELC.1 Overview:As part of the Byersville/ Harper Creek Flood Reduction Study, a computer model of watershedhydrology and watercourse hydraulics was developed. The model was developed using the U.S.EPA’s Stormwater Management Model Version 4 (Huber et al., 1988), operated using thePCSWMM2005 interface.Development and application of the model is described in detail in the Byersville/Harper CreekFlood Reduction Study Final Report (April 2009) prepared by XCG Consultants Ltd., for theCity of Peterborough.In summary, the model is as follows:1. For modelling purposes, the watershed was subdivided into 42 constituent subcatchmentsbased on considering topography and drainage systems.2. Computation of runoff hydrographs from each of these areas is carried out using theRUNOFF object in PCSWMM2005.3. Addition of these flows and routing through the upper watershed (above ClonsillaAvenue) is carried out using the TRANSPORT object in PCSWMM2005.4. For the lower portion of the watershed (below Clonsilla Avenue), flows are added androuted using the EXTRAN object of PCSWMM2005. The EXTRAN object provides fulldynamic routing of flows and accounts for storage effects associated with channel orfloodplain storage. The EXTRAN object allows for representation of backwater effectsand of impacts of flood conditions in the main outlet channels on conditions withintributary storm sewer systems.For the purposes of updating the flood-risk mapping for the lower Byersville Creek watershed(i.e. below Lansdowne Street West), it was necessary to make some modifications to the modelto better represent surface flow patterns that were reported to have occurred during the floodevent of July 14-15, 2004, with respect to the residential area south of the former CNR rail tracks(now a recreational pathway) in the area of Orpington Road, Cameron Street, Mountain AshRoad, Erskine Avenue, and vicinity.C.2 Model ModificationsThe modifications consisted of the following:XCG file 3-2087-09-01 APPENDIX C Page 1 of 11Aug 11, 2010Update of PCSWMM Model

C.2.1 Subcatchment Refinements:Refinement of subcatchment delineations to better represent flow distribution along the system,as follows (See Figure C-1):• Subcatchment 5 was subdivided into two catchment areas (5A and 5B; see Figure C-1) withtheir location of outflow to Byersville Creek being as indicated on Figure C-2 (modelschematic diagram) presented below.• Subcatchment 8 was subdivided into subcatchments 8A (west of Erskine Ave) and 8B (east ofErskine Ave) to better discriminate between areas draining directly into the Examiner Ditch,versus area that drains into the Erskine Avenue storm sewer upstream of the Examiner Ditchinflow to the sewer.C.2.2 Additional of Hydraulic Routing Elements:A detailed elsewhere in this report, investigations including survey of local residents werecompleted to obtain further information on where surface flooding and surface flow happened inthe event of July 14-15, 2004, particularly in the area south of the former CNR line. It wasdetermined that flow had overtopped the former CNR line and contributed to surface flow andflooding in the area to the south. A number of flow routes were reported by local residents andconfirmed from available photographs from various sources including ORCA and local residents.These include:• Flow overtop of and some washout of the former CNR rain embankment at the east end ofCameron Street, and in the vicinity of the east end of Orpington Road (where the ExaminerDitch makes a 90 o turn to the east)• Surface flow along Orpington Road, Cameron Street, Erskine Avenue, Crawford Drive; andfrom Crawford Drive onto Mountain Ash Road and once Robert Road.• Surface flooding and flow along Stocker Road and along Barnes Crescent.Details of the available observations are provided on a map figure elsewhere in this report.On this basis, and using review of available topographic and ground survey information, anumber of hydraulic elements were added to the PCSWMM2005 EXTRAN object.Figure C-2 provides a schematic diagram of the modified model that depicts the various elementsthat have been included to represent the various observed and potential overland flow paths inthe area south of the former CNR line.XCG file 3-2087-09-01 APPENDIX C Page 2 of 11Aug 11, 2010Update of PCSWMM Model

Figure C-1Subcatchment Boundaries forPCSWMM Runoff ModelUpdated April 2010LILY LAKE RD!(FAIRBAIRN STLegend4!( OutfallsStorm SewersCHEMONG RD!(!(WatercoursesWaterbodies15!(!(Drainage BoundaryRailwayACKISON RDMONAGHAN RDPARKHILL RD!(!(!(28!(StreetsLot LinesWELLER STPARK STElevation ContoursWALLIS DRFAIR AVE!(!(Cedar GroveSWM Pond!(1816!(!(!(!(!(25CHARLOBREALEY DR!(192034!(Kawartha HeightsPark Pond!(1731!(!(!(372135!(29HIGH STERBROOKE ST13GolfCoursePond30!(!(36GOODFELLOW RD23!(!(!(27!(24!(33321439!(1!( !( !(!(!(!(26!(!(!(!(!(!( !(!(!(98.1LANSDOWNEERSKINE AVE382240RYE ST10!(!(!(8.212416!(!(11!(DOBBIN RDBREALEY DRDobbin RoadSWM Pond!(!(!(SPILLSBURY DR!(College ParkSWM Pond!(!(!(!(!(DRARKWAY75.2!(5.1CRAWFORD DR!(43!(!(0 400 800Meters2!(!(

FIGURE C-2: SCHEMATIC OF MODIFIED PCSWMM EXTRAN MODEL, Lower Byersville Creek watershedXCG file 3-2087-09-01 APPENDIX C Page 4 of 11Aug 11, 2010Update of PCSWMM Model

C.3 Model Application and ResultsC.3.1 Rainfall InputsThe modified PCSWMM model was used to simulate flow hydrographs for two events:• The event of July 14-15, 2004• The Regional Storm event, referred to as the Zone 3 Regional Storm or the “Timmins event”,as prescribed for flood-risk mapping studies by the technical guidelines published by theOntario Ministry of Natural Resources (OMNR, 2002).The rainfall data used to model the July 2004 event was developed from radar rainfall intensitydata supplied by the City of Peterborough during the Byersville/Harper Creek Flood ReductionStudy. As documented in the Byersville/Harper Creek Flood Reduction Study Report, AppendixF, XCG Consultants reviewed the radar rainfall data for a set of 1-km 2 radar grid cells thatencompass the Byersville Creek watershed. The radar rainfall data were scaled to provide eventtotal rainfall that matches with available ground measurements of rainfall amount. The result ofthis analysis was development of a rainfall time series comprised on rain amounts for each 10-minute interval, describing the rainfall that occurred over the Byersville Creek watershedbetween 4:00 on July 14, 2004 and 22:00 on July 15, 2004, with the total rainfall amount being151.3 mm. See event plot below.Rainfall of July 14-15, 2004 over Byersville Creek watershedXCG file 3-2087-09-01 APPENDIX C Page 5 of 11Aug 11, 2010Update of PCSWMM Model

For the Regional Storm, the event rainfall was as described in the Ontario Ministry ofTransportation Drainage Manual, Chapter H (Design Chart H3-3a) for the Zone 3 RegionalStorm, consisting of 193 mm of rainfall in 12 hours.A comparison the Regional Storm with the July 2004 event is provided below.Comparison of rainfall of July 14-15, 2004over Byersville Creek with Zone 3 Regulatory eventJuly 14-15, 2004 Event OverByersville Creek WatershedRegulatory TimminsStormTotal event 151 mm in 42 hours 193 mm in 12 hrsMaximum amount in 1 hour 46 mm 43 mmMaximum amount in 2 hours 71 mm 63 mmMaximum amount in 6 hours 98 mm 132 mmMaximum amount in 12 hours 118 mm 193 mmBased on the above table alone, it is not immediately apparent as to whether the July 2004 eventwould be a more severe event over Byersville Creek watershed than the Timmins event. At the1-hour and 2-hour durations, the July 2004 event was more intense. As noted in the 1990 FloodRisk Mapping Study, and also determined by modelling during the Byersville/Harper CreekFlood Reduction Study (XCG, 2009), this is the range of critical storm duration for theByersville Creek watershed.XCG file 3-2087-09-01 APPENDIX C Page 6 of 11Aug 11, 2010Update of PCSWMM Model

C.3.2 Model Results for Event of July 2004Figure C-3 presents peak flows computed by the PCSWMM2005 EXTRAN model of LowerByersville Creek, for the event of July 14-15, 2004. This figure provides a detailed examinationof simulated peak flows within the area south of Lansdowne Street West.The peak flows from the PCSWMM2005 EXTRAN model were used as input to the steady-stateHEC-RAS model, in order to compute water surface elevations and allow mapping of surfaceflooding areas.The performance of the PCSWMM EXTRAN model has been assessed by examining how wellit replicates what is known to have actually occurred during the event of July 2004. Thisassessment was based on considering the magnitude of surface flows computed by the model atvarious locations (e.g. along Orpington Road, Cameron Street, Crawford Drive, ErskineAvenue), and by examining the resulting mapping of surface flooding.As indicated on Figure C-3, three separate cases were modelled to help with examining howsensitive the results are to assumptions about what actually happened at some critical locations.• There were reported to have been washouts of the former CNR rail embankment at twolocations, and very rough dimensions of the washout were provided by local residents.• As well, XCG’s site investigations showed that the location at which the Examiner Ditch flowsinto the Erskine Avenue storm sewer in prone to debris accumulation and blockage. Seephotos below.The model has been used to simulate the flow hydrographs for three scenarios:Case 1Case 2Case 3No washout of the former CNR, and no blockage of the Erskine Avenue storminlet on Examiner DitchNo washout of the former CNR, and 60% blockage of the Erskine Avenue storminlet on Examiner DitchRepresentation of reported washouts of the former CNR, and 60% blockage of theErskine Avenue storm inlet on Examiner DitchThe model proved to be most sensitive to the presence or absence of the CNR washouts, and lesssensitive to whether there was blockage at the storm sewer inlet.It was found that Case 3 results in the most realistic representation of what actually happenedduring the event of July 2004, indicating that the reported CNR washouts and resulting flowconveyance from north of the CNR to the south were a significant contributing factor to theobserved surface flooding to the south of the CNR.Figure 3.2 in the main body of this report shows the extent of surface flooding for Case 3.XCG file 3-2087-09-01 APPENDIX C Page 7 of 11Aug 11, 2010Update of PCSWMM Model

Photo date May 28, 2007Photo date May 28, 2007Photo date Feb. 5, 2010Photos of Debris Accumulation at Examiner Ditch Inlet to Erskine Avenue Storm SewerXCG file 3-2087-09-01 APPENDIX C Page 8 of 11Aug 11, 2010Update of PCSWMM Model

C.3.2 Model Results for Regional Storm EventFigure C-4 presents peak flows computed by the PCSWMM2005 EXTRAN model of LowerByersville Creek, for the Regional Storm event.As with the July 2004 event, peak flows from the PCSWMM2005 EXTRAN model were used asinput to the steady-state HEC-RAS model, in order to compute water surface elevations andallow mapping of surface flooding areas.The model has been used to simulate the flow hydrographs for the Regional Storm, for threescenarios:Case 1Case 2Case 4No washout of the former CNR, and no blockage of the Erskine Avenue storminlet on Examiner Ditch; existing twin 2.0-m CSP culverts under CPR east of TheParkway (head end of Examiner ditch)No washout of the former CNR, and 60% blockage of the Erskine Avenue storminlet on Examiner Ditch; existing twin 2.0-m CSP culverts under CPR east of TheParkway (head end of Examiner ditch)Representation of reported washouts of the former CNR, and 60% blockage of theErskine Avenue storm inlet on Examiner Ditch; single 1.0-m culvert under CPReast of The Parkway (proposed replacement of the existing twin 2.0-m CSPculverts) at head end of Examiner ditch.Case 1 has been used for generating updated flood-risk mapping for the existing system. Figure3.3 in the main body of this report shows the results for Case 1.Case 2 has been used only to examine model sensitivity to blockage of this storm sewer inlet.Case 4 has been examined to determine the net effect of the proposed culvert replacement(downsizing) at the top end of the Examiner Ditch, on the flood-risk area. Figure 3.4 in the mainbody of this report shows the results for Case 4.XCG file 3-2087-09-01 APPENDIX C Page 9 of 11Aug 11, 2010Update of PCSWMM Model

WEBBER AVRYE STMOUNTAIN ASH RDROBERT RDERSKINE AVBARNES CRSURVEY STSTORNOWAY PLIN PLCHAMBERLAIN STARTHUR AVFigure C-3Peak Flows from PCSWMMEXTRAN ModelJuly 15, 2004 Storm EventDUFFUS STBROWN STGRADY AVREYNOLDS CTBROWN STLUNDY'S LNNOBLE PLRALPHSON CRWENTWORTH STGOODFELLOW RDWIGHTMAN AVFORD STNEW ROMAINE STModelling Scenarios:Case 1 - no washout at former CNR,no storm sewer inlet blockageCase 2 - no washout, 60% blockageat Erskine Avenue storm inletCase 3 - same as Case 1, but with CPR3+CPR4replaced by single 1.0m culvertST MARY'S STST MARY'S STMERVIN AVROMAINE ST307330731 - 47.62 - 47.63 - 47.6ARTHUR AVLdwn 30501 - 49.1, 7.52 - 49.1, 7.53 - 49.1, 7.530503025LANSDOWNE30251 - 56.32 - 56.33 - 56.2LegendHarper 11 - 8.882 - 8.883 - 8.88Harper 1233223321 - 44.32 - 44.33 - 44.328831 - 43.32 - 43.33 - 43.32506CPR1 + CPR2(Twin 3.6m CSP culverts)2883CPR1 + CPR21 - 60.702 - 60.703 - 60.7025061 - 43.32 - 43.33 - 43.3Pkwy Sp11 - 12.92 - 12.93 - 12.9Pkwy Sp1CPR3 + CPR4(Twin 2.0m CSP culverts)E2CROWN DRE21 - 12.82 - 12.83 - 12.8E3THE KINGSWAYCPR3 + CPR41 - 12.82 - 12.83 - 12.8E31 - 12.82 - 12.83 - 12.8E6E61 - 10.42 - 10.33 - 10.5THE QUEENSWAYE19BORDEN AVE191 - 2.152 - 1.903 - 1.91E16ERSK61 - 4.712 - 4.743 - 3.08#Peak Flow, Case 1# # #Model Conduit ID andFlow DirectionModel Conduit IDPeak Flow, Case 2Peak Flow, Case 3MCKELLAR STHAWLEY STLITTLE STTHE PARKWAYCrawford1 - 63.22 - 63.43 - 63.122751800bThe Parkway1800a1565aCrawford152722751 - 60.72 - 60.73 - 60.71800b1 - 60.02 - 60.03 - 60.0The Parkway1 - 64.22 - 64.23 - 64.21800a1 - 64.132 - 64.103 - 64.101565a1 - 62.52 - 63.63 - 62.915271 - 63.12 - 63.33 - 63.015401565a1 - 02 - 03 - 0KINGSWAY CTCAMERON PLE131 - 4.202 - 4.303 - 4.10E111 - 3.472 - 3.563 - 3.00E13E11E151 - 0.042 - 0.343 - 1.01QUEENSWAY CTE8E10E16E18RECREATIONAL PATHWAY (FORMER CNR LINE)E15E81 - 10.22 - 9.83 - 10.4E101 - 8.392 - 9.363 - 8.85E141 - 2.582 - 2.493 - 3.48E161 - 2.202 - 3.693 - 5.18E181 - 0.002 - 0.003 - 1.22E14E91 - 3.12 - (-3.1)3 - (-3.0)BYERSVILLE CREEKE9E17E171 - 1.842 - 2.993 - 4.10E20E201 - (-0.25)2 - (-0.17)3 - 1.21STOCKER RDCRAWFORD DRERSK2ERSK3ERSK4ERSK6ERSK7ERSK8ERSK21 - 02 - 03 - 0GILLESPIE AVORPINGTON RDERSK31 - 1.192 - 0.843 - 1.73ERSK41 - 2.192 - 2.273 - 4.64CAMERON STERSK61 - 4.522 - 4.563 - 6.58ERSK71 - 1.732 - 1.773 - 3.06ERSK81 - 3.272 - 3.413 - 6.02BARBARA CRBELLAIRE STCRAWFORD PLNote:Conduits ERSK2 toERSK8 representoverland flow alongErskine Avenue.The EXTRAN Modelalso includes theErskine Avenuestorm sewer fromMcKellar Streetsouth to ByersvilleCreek.Surcharge of thestorm sewer cancontribute tooverland flowalongErskine Avenue.SHIRLEY AVHAROLD PLHARO7 & 115 HY1300b1300b1 - 62.92 - 63.13 - 62.81187 865 0543b 0543a 223 Mghn Outlet11871 - 62.32 - 62.43 - 62.18651 - 62.02 - 62.03 - 61.70543b1 - 62.52 - 62.53 - 62.10543a1 - 71.32 - 71.3JOHNSTON DR3 - 74.22231 - 72.72 - 72.63 - 75.2Outlet1 - 72.72 - 72.63 - 75.2

WEBBER AVRYE STMOUNTAIN ASH RDROBERT RDERSKINE AVBARNES CRSURVEY STSTORNOWAY PLIN PLCHAMBERLAIN STARTHUR AVFigure C-4Peak Flows from PCSWMMEXTRAN ModelRegional Storm EventDUFFUS STBROWN STGRADY AVREYNOLDS CTBROWN STLUNDY'S LNNOBLE PLRALPHSON CRWENTWORTH STGOODFELLOW RDWIGHTMAN AVFORD STNEW ROMAINE STModelling Scenarios:Case 1 - no washout of former CNR,no storm sewer inlet blockageCase 2 - no washout, 60% blockageat Erskine Avenue storm inletCase 4 - same as Case 1, but with CPR3+CPR4replaced by single 1.0m culvertST MARY'S STST MARY'S STMERVIN AVROMAINE ST307330731 - 47.42 - 47.14 - 47.1ARTHUR AV30503025LANSDOWNE30251 - 55.22 - 55.54 - 55.2LegendHarper 11 - 8.82 - 8.84 - 8.8Harper 1233223321 - 44.12 - 44.34 - 44.128831 - 43.12 - 43.14 - 43.12506CPR1 + CPR2(Twin 3.6m CSP culverts)288325061 - 43.12 - 43.14 - 43.1CPR1 + CPR21 - 60.82 - 61.04 - 60.8Pkwy Sp11 - 12.102 - 12.364 - 12.10Pkwy Sp1CPR3 + CPR4(Twin 2.0m CSP culverts)E2CROWN DRE21 - 11.82 - 11.94 - 5.30E3THE KINGSWAYCPR3 + CPR41 - 11.82 - 11.94 - 5.30E6E61 - 9.62 - 9.64 - 5.1THE QUEENSWAYE19BORDEN AVE191 - 1.952 - 1.644 - 1.82E16ERSK61 - 4.712 - 4.744 - 3.08#Peak Flow, Case 1# # #Model Conduit ID andFlow DirectionModel Conduit IDPeak Flow, Case 2Peak Flow, Case 4MCKELLAR STHAWLEY STLITTLE STTHE PARKWAYCrawford1 - 62.62 - 62.74 - 61.622751800bThe Parkway1800a1565aCrawford152722751 - 60.82 - 61.14 - 60.81800b1 - 59.52 - 59.84 - 59.1The Parkway1 - 63.42 - 63.94 - 63.41800a1 - 63.32 - 63.94 - 63.31565a1 - 64.02 - 63.34 - 62.515271 - 62.52 - 62.64 - 61.615401565a1 - 02 - 04 - 0KINGSWAY CTCAMERON PLE131 - 3.732 - 3.824 - 2.66E111 - 3.382 - 3.484 - 2.94E13E11E151 - 0.002 - 0.124 - 0.00QUEENSWAY CTE8E10E16E18RECREATIONAL PATHWAY (FORMER CNR LINE)E15E81 - 9.232 - 9.254 - 5.20E101 - 7.482 - 8.344 - 3.76E141 - 2.852 - 2.494 - 1.60E161 - 1.282 - 2.744 - 0.50E181 - 02 - 04 - 0E14E91 - 2.52 - (-3.0)4 - 3.3BYERSVILLE CREEKE9E17E171 - 1.272 - 2.464 - 0.44E20E201 - (-0.20)2 - (-0.97)4 - 0.08STOCKER RDCRAWFORD DRERSK2ERSK3ERSK4ERSK6ERSK7ERSK8ERSK21 - 02 - 04 - 0GILLESPIE AVORPINGTON RDERSK31 - 1.362 - 0.964 - 0.90ERSK41 - 2.052 - 2.134 - 0.75CAMERON STERSK61 - 4.712 - 4.744 - 3.08ERSK71 - 1.862 - 2.004 - 0.95ERSK81 - 4.032 - 3.914 - 1.75BARBARA CRBELLAIRE STCRAWFORD PLNote:Conduits ERSK2 toERSK8 representoverland flow alongErskine Avenue.The EXTRAN Modelalso includes theErskine Avenuestorm sewer fromMcKellar Streetsouth to ByersvilleCreek.Surcharge of thestorm sewer cancontribute tooverland flowalongErskine Avenue.SHIRLEY AVHAROLD PLHARO7 & 115 HY1300b1187 865 0543b 0543a 223 Outlet11871 - 61.92 - 62.04 - 61.18651 - 61.72 - 61.74 - 60.80543b1 - 62.52 - 62.44 - 61.60543a1 - 72.32 - 72.1JOHNSTON DR4 - 68.62231 - 73.52 - 72.54 - 69.7Outlet1 - 73.52 - 72.54 - 69.7

City of PeterboroughLower Byersville Creek Flood-Risk Mapping UpdateAPPENDICESAPPENDIX DHEC-RAS MODEL DETAILS3-2087-09-01/R_3-04108226_Byersville Creek_Mapping Update08/11/10D

APPENDIX DUPDATE OF HEC-Ras MODELD.1 Overview:In order to conduct the analysis of flood levels in the lower area of Byersville Creek, existing hydraulic models approved and providedby the local Conservation Authority were screened, modified and applied, as applicable. The overall HEC-Ras model of the study areahas three (3) distinctive components:1. Main Branch of Byersville Creek from Clonsilla Ave. to the outlet at Otonabee River2. Examiner Ditch, between CPR track and Erskine Ave; and3. CNR Ditch representing a spill path from Examiner Ditch along the former CNR tracks to Main Creek upstream of CrawfordDr.In addition, a new model section was developed for the area immediately south of CNR tracks and east of Erskine Ave to evaluatespills from Examiner Ditch over the CNR berm. This fourth (4 th ) model is referred to as the Lower Spill model (CNR Spill Area).Figures D-1 to D4 provides a schematic of the above noted HEC-Ras model components.Upon review and updates of existing models, baseline condition models were established for further hydraulic analysis. The baselineconditions for the CNR spill area has been determined by refining model parameters to achieve observed flood records (within reason)during the July 15 th 2004 storm event, using flows generated using PCSWMM watershed model.A number of modeling assumptions and professional judgment based on experience and field observations were applied to completethe hydraulic analysis and determine the extent of flooding. The modeling scenarios summarized in Table D-1 were used to generateflood levels at key locations.FIGURE D-1 Byersville Creek - Main BranchFIGURE D-2 Examiner Ditch modelXCG file 3-2087-09-01 APPENDIX D Page 1 of 16Update of HEC-Ras Model

FIGURE D-3 Examiner Ditch West Spill model: Spill along CNR towards Crawford Dr.FIGURE D-4 Lower Spill model : CNR Spill Area – Spill towards Erskine Ave.D.2 Model ModificationsIn summary, the model(s) modifications consisted of the following:1. New cross-sections were generated using DEM model and/or survey information;2. Local modification to existing cross-sections were applied to better represent intent of this analysis;3. “n” values and contraction/expansion coefficients were updated, where applicable;4. Reduction in storage areas due to building structures and/or local storage areas accounted for in the PCSWMM model wereapplied, where applicable;5. Weirs were incorporated at identified spill/hydraulic connectivity locations for verification purposes;6. Starting water levels were evaluated and selected as per attached Table D-2;7. CPR culvert structures were updated, as required, to reflect modelling scenarios.D.3 Model verification – CNR Spill AreaThe verification of flood levels in the lower area of Byersville Creek, especially in the spill area south of the CNR tracks, wascompleted using available flood records. Estimated flow depths, flow directions, extent of flooding, high water marks were reviewedand used as reference to simulate similar water level conditions using July 14-15, 2004 flows.Iteration of water levels at locations representing hydraulic connectivity (e.g. at the Parkway), including spills and/or temporary redirectionof flows from the main creek, backwater effect, was performed to achieve reasonable water levels as per observed records, aswell as, balanced water levels within the HEC-Ras model at the points of model intersections/convergence.D.4 Model ResultsThe summary of modelling results, including key parameters such, applied flow, computed water level, flood width and flow velocityat each cross-section is presented in the attached Tables D-3 to Table D-14.A visual representation of the estimated extent of flooding during the Regional (Timmins) Storm event is provided in Figure 3.3 andFigure 3.4 in the main report. The key modelling scenarios used to simulate the flooding conditions are Case 1 and Case 4, asdiscussed in the main report.Accordingly, Figure 3.3 presents the results of flooding conditions within the study area during July 14-15, 2004 storm event usingCase 3 modelling scenario.XCG file 3-2087-09-01 APPENDIX D Page 2 of 16Update of HEC-Ras Model

Table D-2: Starting water elevations applied in HEC-RAS modelsModel # Location Storm EventModellingScenario/CaseHEC-RasCross-Sec.WL Comment 1 Comment 21Byersville Creek Main Branch: Clonsill Avenue toOutlet at Otonabee RiverJuly 14-15, 2004Flooding Event3 18 186.75A summer navigable water elevation on the OtonabeeRiver as per Note 1. A critical depth occurs at theculvert, thus, upstream water levels are not affectedby downstream water levels during significant flowevents such as Regional and July 2004 events.ORCA Model: used mean WLs on Otonabee River/ Allsections looking upstream/Base geometry from1990&1996. Local updates from site developmentapplications.Timmins RegionalStorm1 & 4 18 187.00Estimated high water level on Otonabee River duringMarch 1999 was applied. Note 3.2 Lwer Spill. Model: Southeast of former CNR lineJuly 14-15, 2004Flooding Event3 543 190.36Downstream water level based on estimated waterlevel along the main creekReference xsec. 543 - Main Ck model3 450CriticalDepthUpstream water levels estimated on the south side ofCNR using PCSWMM model. Critical depth occurs inHEC-Ras model.WL at extension of the Examiner Ditch = 191.51m; WL atCameron St = 191.67mTimmins RegionalStorm1 & 4 543 190.37Downstream water level based on estimated waterlevel along the main creekReference xsec. 0+543 - Main Ck model1 & 4 450CriticalDepthUpstream water levels estimated on the south side ofCNR using PCSWMM model. Critical depth occurs inHEC-RAS model.Case 1: WL at extension of the Examiner Ditch =191.47m; WL at Cameron St = 191.48m; Case 4:Negligeble spill at Cameron St at CNR tracks3Examiner Ditch Model: From CPR trackssouthward to inlet to Erskine Avenue storm sewerJuly 14-15, 2004Flooding Event3 1050 192.01 Water levels estimated using PCSWMM model.1 & 4 1050 RC Rating Curve as per D.M. Willis HEC-RAS modelTimmins RegionalStorm1 & 4 1050 RC Rating Curve as per D.M. Willis HEC-RAS model4Examiner Ditch West Spill Model: Spill flow fromExaminer Ditch southwestward along former CNRrail lineJuly 14-15, 2004Flooding Event3 1327 192.01Water levels estimated using HEC-RAS "ExistingExaminer Ditch" modelNode 9 in PCSWMM ModelTimmins RegionalStorm1 & 4 1327 191.95Water levels estimated using HEC-RAS "ExistingExaminer Ditch" modelNode 9 in PCSWMM ModelNotes:1. Starting water surface elevations at the outlet of Byersville Creek, as per "Byersville Creek Two-Zone Concept Assessment for Floodplain Planningand Encroachment Analysis"; Greenland International Consulting (Sept. 2003)188.50 m Flood Stage on Otonabee River186.75 m A summer navigable water elevation on the Otonabee River (similar to 1990 Peterborough Flood Risk Mapping Study).This elevation was applied to derive a rating curve at the outlet for unsteady flow analysis.2. Estimated water level at the Beyersville Creek outlet during the July 14-15, 2004 storm event using high water marks189.6 m Monaghan Rd. Debris line, as per "July 2004 Flood" Report; John W. Merriam & Associates (2005)High water mark record at Johnston Drive outlet "High Water Mark Description- Peterborough Flood";John W. Merriam & Associates (May 2005).189.3 m South armour stone plus 0.3m - elevation estimated using culvert data (record drawing)3. Culvert Data - Outlet to Otonabee RiverTop of RoadTop of StructureTop of ArmourSummer Water Level VarianceWater Level March 24, 1999190.97 m188.90 m189.00 m186.59 m186.72 m186.895 mRef. Dwg. 2335SP01-PUCU2; Sheet No.1 (March 2000)

TABLE D-3HEC-RAS RESULTS for EVENT OF JULY 14-15, 2004Model Scenario Case 3: Washouts at former CNR modelled, and 60% blockage of Erskine Avenue storm inletMAIN BRANCH Model ‐ CASE 3River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaTop Froude #Width Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)3645 July 15 2004 37.2 199.17 200.37 200.37 200.77 0.013833 2.79 13.34 16.84 13554 July 15 2004 47.6 197.06 198.79 198.83 199.36 0.014091 3.35 14.22 14.01 1.063390 July 15 2004 56.2 194.79 196.74 197.08 197.44 0.009629 4.25 18.68 29.05 0.993165 July 15 2004 56.2 193.68 196.25 195.9 196.3 0.000905 1.47 70.64 243.57 0.313073 July 15 2004 56.2 193.29 196.15 195.33 196.2 0.001195 1.37 75.64 145.53 0.263068 July 15 2004 56.2 193.29 196.15 195.81 196.2 0.000347 1.37 122.69 216.78 0.263047 Lansdowne Bridge3026 July 15 2004 56.2 193.23 195.81 195.81 196.02 0.001255 2.47 59.33 152.72 0.493025 July 15 2004 56.2 193.23 195.76 195.27 195.78 0.000769 1.04 84.45 194.34 0.213023 July 15 2004 56.2 193.23 195.76 195.26 195.78 0.000622 0.93 84.47 193.77 0.193009 July 15 2004 56.2 193.23 195.75 195.26 195.77 0.000648 0.95 83.27 189.91 0.192999 July 15 2004 56.2 193.23 195.74 195.26 195.77 0.000669 0.96 82.39 188.47 0.22993 July 15 2004 56.2 193.23 195.73 195.26 195.76 0.000682 0.97 81.84 187.54 0.22986 July 15 2004 56.2 193.23 195.73 195.26 195.76 0.000698 0.98 81.21 226.35 0.22969 July 15 2004 56.2 193.08 195.74 195.75 0.000118 0.46 166.46 304.31 0.092961 July 15 2004 56.2 193.08 195.74 195.75 0.000135 0.58 166.03 299.02 0.112947 July 15 2004 56.2 192.9 195.74 195.74 0.00011 0.47 213.4 342.21 0.092940 July 15 2004 56.2 192.9 195.74 194.59 195.74 0.000093 0.43 205.89 243.61 0.082939 July 15 2004 56.2 192.9 195.74 194.59 195.74 0.000116 0.48 188.78 243.23 0.092917 July 15 2004 56.2 192.9 195.73 194.6 195.74 0.000106 0.46 205.21 243.57 0.092889 July 15 2004 56.2 192.9 195.73 195.74 0.000076 0.39 257.14 337.02 0.072883 July 15 2004 56.2 192.25 195.73 194.24 195.74 0.000069 0.42 225.19 260.97 0.082703 July 15 2004 56.2 192.01 195.72 195.72 0.000053 0.44 199.42 318.93 0.082662 July 15 2004 56.2 191.95 195.71 195.72 0.000098 0.64 157.84 121.92 0.112512 July 15 2004 56.2 191.5 195.71 195.71 0.000036 0.43 251.95 172.23 0.072506 July 15 2004 43.3 191.2 195.71 195.71 0.000038 0.45 185.5 143.14 0.072332 July 15 2004 60.7 190.6 195.7 195.71 0.000033 0.43 242.99 140.53 0.062320 July 15 2004 60.7 190.6 195.68 193.12 195.7 0.000121 0.78 139.11 169.65 0.122310 CPR TRACKS Bridge2300 July 15 2004 60.7 190.3 192.81 192.81 193.8 0.007723 4.4 13.81 38.53 12275 July 15 2004 60.7 189.69 192.93 191.92 193.16 0.001682 2.42 33.92 19.52 0.452148 July 15 2004 60.7 189.6 192.92 191.64 192.98 0.000653 1.19 92.94 148.21 0.252031 July 15 2004 60.7 189.5 192.68 192.85 0.00197 1.81 34.21 21.56 0.431845 July 15 2004 64.2 188.81 192.69 192.71 0.000232 0.99 193.49 457.25 0.171839 July 15 2004 64.2 188.95 192.66 190.33 192.71 0.000178 0.97 66.09 97.85 0.171823 THE PARKWAY Bridge1807 July 15 2004 64.2 188.95 192.36 190.33 192.4 0.000191 0.95 110.56 85.13 0.171800 July 15 2004 64.1 188.68 192.35 192.4 0.000578 1.61 136.07 330.62 0.271765 July 15 2004 64.1 188.82 191.99 191.11 192.33 0.00279 3.21 51.41 407.68 0.581705 July 15 2004 64.1 188.34 191.99 191.34 192.15 0.001777 2.33 74.46 610.72 0.411645 July 15 2004 64.1 188.32 191.67 191.37 191.98 0.003505 3.07 48.39 525.4 0.561585 July 15 2004 64.1 188.29 191.71 191.04 191.8 0.001224 2.18 107.73 410.92 0.381565 July 15 2004 62.9 188.28 191.74 191.77 0.000584 1.52 169.35 277.62 0.271552 July 15 2004 62.9 188.2 191.75 189.52 191.76 0.000029 0.33 231.13 357.31 0.081543 CRAWFORD Culvert1534 July 15 2004 62.9 188.2 191.54 189.52 191.55 0.000045 0.39 173.82 217.87 0.11527 July 15 2004 63.1 188.47 191.53 191.55 0.000297 0.98 165.54 317.72 0.191346 July 15 2004 63.1 188.22 191.45 190.7 191.49 0.00055 1.34 86.89 99.98 0.241322 July 15 2004 63.1 188.08 191.05 191.33 0.002453 2.53 31.07 18.84 0.521305 July 15 2004 62.8 188.2 191.09 191.26 0.00163 2.32 66.76 166.21 0.441187 July 15 2004 62.8 187.54 190.89 191.06 0.001836 2.25 50.91 85.79 0.421025 July 15 2004 62.8 187.44 190.71 190.81 0.001183 1.81 62.02 70 0.33865 July 15 2004 62.8 187.42 190.55 190.62 0.001035 1.64 62.78 44.85 0.31725 July 15 2004 62.1 187.39 190.38 190.48 0.000968 1.5 49.63 31.86 0.32543 July 15 2004 62.1 187.33 190.36 190.38 0.000242 0.89 138.84 193.61 0.17384 July 15 2004 62.1 186.93 190.33 190.34 0.000177 0.75 179.88 390.96 0.13223 July 15 2004 72.7 186.6 190.29 190.31 0.000302 1 177.43 293.28 0.1883 July 15 2004 72.7 186.29 190.26 190.28 0.000144 0.8 149.14 127.6 0.1355 July 15 2004 72.7 186.6 190.26 190.2 190.27 0.000084 0.6 223.33 146.19 0.142.5 JOHNSTON Bridge30 July 15 2004 72.7 186.3 189.14 188.79 189.16 0.000347 1.03 115.66 80.93 0.227 July 15 2004 72.7 186.37 188.15 188.15 188.93 0.012399 3.92 18.54 11.84 124 July 15 2004 72.7 186.3 187.27 187.73 188.79 0.044997 5.48 13.27 14.5 1.8321 July 15 2004 72.7 186.23 186.96 187.43 188.62 0.067276 5.71 12.73 18.1 2.1718 July 15 2004 72.9 186.16 186.8 187.25 188.38 0.074041 5.57 13.09 20.95 2.25

TABLE D-4HEC-RAS RESULTS for EVENT OF JULY 14-15, 2004Model Scenario Case 3: Washouts at former CNR modelled, and 60% blockage of Erskine Avenue storm inletRiver Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)2050 July 15 2004 12.9 192.9 195.00 193.99 195.04 0.000599 0.82 15.65 111.86 0.211978 July 15 2004 12.8 192.69 194.91 193.57 194.98 0.000551 1.14 11.25 94.81 0.241974 Culvert1964 July 15 2004 12.8 192.6 193.60 193.54 193.97 0.010203 2.72 4.71 17.66 0.91950 July 15 2004 12.8 192.46 193.56 193.65 0.00426 1.9 13.75 30.34 0.591882 July 15 2004 12.8 191.85 193.21 193.21 193.34 0.005135 1.95 12.83 47.91 0.621850 July 15 2004 12.8 191.65 193.08 192.72 193.11 0.001133 1.01 20.57 45.55 0.31800 July 15 2004 12.8 191.35 193.06 193.07 0.000524 0.78 28.69 55.61 0.211777 July 15 2004 12.8 191.22 193.06 192.43 193.06 0.000142 0.2 69.23 175.64 0.11770 Culvert1763 July 15 2004 12.8 191.19 193.06 193.06 0.000011 0.06 283.47 908.01 0.031700 July 15 2004 12.8 191.24 193.06 193.06 0.000021 0.11 224.44 749.38 0.041610 July 15 2004 12.8 191.12 193.05 193.05 0.000066 0.28 161.31 532.98 0.071553 July 15 2004 12.8 191.26 192.96 193.01 0.001251 1.1 14.76 24.7 0.321500 July 15 2004 12.8 191.06 192.95 192.97 0.000354 0.77 21.17 20.48 0.191458 July 15 2004 10.5 190.8 192.87 191.62 192.93 0.0006 1.13 9.27 336.26 0.251442 Culvert1428 July 15 2004 10.5 190.48 192.39 192.49 0.001139 1.42 7.37 77.73 0.341427 Lat Struct1405 July 15 2004 10.5 190.45 192.36 192.44 0.001257 1.41 10.91 12.68 0.341327 July 15 2004 10.4 190.35 192.12 192.22 0.001716 1.53 9.24 11.08 0.391250 July 15 2004 3 190.01 192.08 192.09 0.000167 0.43 8.77 12.32 0.11194 July 15 2004 3 190.28 192.06 191.01 192.08 0.000366 0.63 8.49 67.05 0.161123 July 15 2004 3 190.35 192.03 192.05 0.000524 0.68 8.81 27.23 0.181050 July 15 2004 3 190.67 192.01 191.18 192.02 0.000215 0.36 9.18 12.32 0.12

TABLE D-5HEC-RAS RESULTS for EVENT OF JULY 14-15, 2004Model Scenario Case 3: Washouts at former CNR modelled, and 60% blockage of Erskine Avenue storm inletLOWER SPILL Model (south of former CNR) ‐ CASE 3U/S Starting WL =Critical Depth D/S Starting WL =190.41TopWidthX‐sec.MaxDepthModelEstimatedDepthRiver Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaFroude # ChlGr. Elev. High Water Mark DifferenceFlood Recordreference(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m) (+/‐) Depth WL As per obtained As per obtainedRiver Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl (m) (m) (m) (m) (m) (m) flood records flood records(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)460 Jul‐04 9.8 191.18 191.59 191.45 191.61 0.00076 0.7 57.78 354.09 0.37 0.41 191.4 0.3 191.7 ‐0.11 0.19 ID.4Comment/ Flood Recordreference450 Jul‐04 9.8 191.18 191.57 191.6 0.001086 0.8 44.78 351.04 0.44 0.39 190.9 1.1 192 ‐0.43 0.67 ID. 1400 Jul‐04 9.8 191 191.52 191.54 0.000515 0.62 56.16 292.31 0.31 0.52 190.9 0.8 191.7 ‐0.18 0.62 ID. 10Orpington St/Sag elevation inthe middle of the rd.Orpington St/Sag elevation inthe middle of the rd.Orpington St/Sag elevation in350 Jul‐04 9.8 191.03 191.32 191.32 191.41 0.008777 1.88 31.86 201.26 1.19 0.29 190.9 1.1 192 ‐0.68 0.42 ID. 1the middle of the rd.300 Jul‐04 9.8 190.59 191.16 190.92 191.18 0.000394 0.52 38.71 207.12 0.27 0.57 190.85 0.3 191.15 0.01 0.31 ID. 4 Cameron St250 Jul‐04 10.06 190.76 191 191 191.07 0.007947 1.63 36.31 324.67 1.11 0.24 190.76 0.5 191.26 ‐0.26 0.24 ID. 5 & 6Intersection of Erskine Ave. &Cameron St200 Jul‐04 10.06 190.35 190.83 190.6 190.84 0.000608 0.63 67.44 288.19 0.33 0.48 190.35 0.9 191.25 ‐0.42 0.48 ID.2 Barnes Cr150 Jul‐04 10.06 190.34 190.63 190.61 190.71 0.007116 1.46 24.81 205.59 1.03 0.29 0100 Jul‐04 10.06 189.98 190.41 190.32 190.45 0.001964 0.92 14.66 71.28 0.57 0.43 0

TABLE D-6HEC-RAS RESULTS for EVENT OF JULY 14-15, 2004Model Scenario Case 3: Washouts at former CNR modelled, and 60% blockage of Erskine Avenue stormEXAMINER DITCH WEST SPILL model ‐ CASE 3Spill from Examiner Ditch southwestward along the north side of former CNR track ‐ Case 3River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaTopWidth(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)871 PF 1 8.85 191.33 192.07 191.56 192.07 0.000029 0.11 94.75 225826 PF 1 8.85 191.59 192.04 192.06 0.002888 0.74 14.71 116.94781 PF 1 8.85 191.59 192.02 192.02 0.000298 0.25 32.16 106.62745 PF 1 8.85 191.59 191.91 191.91 191.98 0.017275 1.17 7.41 53.68676 PF 1 8.85 191.17 191.69 191.34 191.70 0.000121 0.18 50.02 126.93626 PF 1 3.00 191.20 191.69 191.69 0.000053 0.09 32.44 121.31606 PF 1 3.00 191.17 191.69 191.69 0.000015 0.06 49.48 126.63578 PF 1 3.00 191.30 191.69 191.69 0.000079 0.1 29.49 141.55508 PF 1 3.00 191.15 191.69 191.69 0.000028 0.06 48.15 179.61448 PF 1 3.00 191.00 191.68 191.69 0.000019 0.06 54.86 193.98294 PF 1 3.00 191.36 191.68 191.68 0.000078 0.07 40.32 251.42281 PF 1 3.00 191.28 191.68 191.68 0.000028 0.05 59.87 339.77266 PF 1 3.00 190.22 191.68 191.68 0.000169 0.19 15.87 46.09222 PF 1 3.00 190.00 191.68 191.68 0.000013 0.06 48.64 123.8172 PF 1 3.00 190.50 191.68 191.68 0.000003 0.03 74.42 161.31159 PF 1 3.00 190.00 191.68 191.68 0.000007 0.05 61.78 173.19152 PF 1 3.00 191.49 191.66 191.68 0.0008 0.54 6.25 71.93142 PF 1 3.00 191.49 191.63 191.63 191.66 0.003082 0.83 3.84 59.14135 PF 1 3.00 191.00 191.14 191.23 191.55 0.351836 2.85 1.05 15.32122 PF 1 3.00 190.28 190.88 190.88 191.03 0.019066 1.74 1.73 5.892 PF 1 3.00 190.00 190.78 190.46 190.79 0.001236 0.53 5.64 14.5150 PF 1 3.00 190.00 190.51 190.51 190.65 0.019821 1.61 1.86 7.27

TABLE D-7HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 1: No washouts at former CNR, and no blockage of Erskine Avenue storm inletMAIN BRANCH Model ‐ CASE 1River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude #Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)3645 Regional 37.4 199.17 200.38 200.38 200.77 0.013833 2.79 13.38 16.84 13554 Regional 47.4 197.06 198.78 198.83 199.35 0.01424 3.36 14.12 13.97 1.073390 Regional 55.2 194.79 196.72 197.06 197.42 0.009666 4.23 18.39 26.02 0.993165 Regional 55.2 193.68 196.24 195.89 196.29 0.000905 1.47 69.65 241.78 0.313073 Regional 55.2 193.29 196.15 195.31 196.2 0.001187 1.36 74.74 144.97 0.263068 Regional 55.2 193.29 196.15 195.81 196.19 0.000343 1.36 121.25 215.2 0.263047 Lansdowne Bridge3026 Regional 55.2 193.23 195.8 195.8 196.02 0.001255 2.46 57.81 150.82 0.493025 Regional 55.2 193.23 195.75 195.27 195.78 0.000753 1.03 84 193.76 0.213023 Regional 55.2 193.23 195.75 195.25 195.78 0.000609 0.92 84.02 193.14 0.193009 Regional 55.2 193.23 195.74 195.25 195.77 0.000635 0.94 82.85 189.25 0.192999 Regional 55.2 193.23 195.74 195.25 195.76 0.000655 0.95 81.99 187.8 0.192993 Regional 55.2 193.23 195.73 195.25 195.76 0.000667 0.96 81.47 186.89 0.22986 Regional 55.2 193.23 195.73 195.25 195.75 0.000682 0.97 80.85 225.81 0.22969 Regional 55.2 193.08 195.74 195.74 0.000115 0.46 165.84 303.79 0.092961 Regional 55.2 193.08 195.73 195.74 0.000131 0.57 165.42 298.49 0.112947 Regional 55.2 192.9 195.73 195.74 0.000107 0.46 212.37 342.18 0.092940 Regional 55.2 192.9 195.73 194.58 195.74 0.000091 0.42 205.18 243.57 0.082939 Regional 55.2 192.9 195.73 194.58 195.74 0.000113 0.47 188.08 242.93 0.092917 Regional 55.2 192.9 195.73 194.59 195.74 0.000103 0.45 204.51 243.54 0.092889 Regional 55.2 192.9 195.73 195.73 0.000074 0.38 256.17 336.62 0.072883 Regional 55.2 192.25 195.73 194.2 195.73 0.000067 0.42 224.49 260.86 0.082703 Regional 55.2 192.01 195.72 195.72 0.000052 0.43 198.99 318.83 0.082662 Regional 43.1 191.95 195.72 195.72 0.000058 0.49 157.97 121.93 0.082512 Regional 43.1 191.5 195.71 195.71 0.000021 0.33 252.45 172.36 0.052506 Regional 43.1 191.2 195.71 195.71 0.000037 0.45 185.7 143.22 0.072332 Regional 60.8 190.6 195.7 195.71 0.000033 0.43 243.18 140.55 0.062320 Regional 60.8 190.6 195.68 193.12 195.7 0.000121 0.78 139.34 170.29 0.122310 CPR TRACKS Bridge2300 Regional 60.8 190.3 192.82 192.82 193.8 0.007704 4.4 13.83 38.62 12275 Regional 60.8 189.69 192.92 191.93 193.16 0.001708 2.44 33.75 19.46 0.452148 Regional 60.8 189.6 192.91 191.64 192.97 0.000673 1.21 91.34 146.11 0.262031 Regional 60.8 189.5 192.67 192.83 0.002032 1.83 33.84 21.39 0.431845 Regional 63.4 188.81 192.66 192.69 0.000254 1.03 182.47 451.64 0.181839 Regional 63.4 188.95 192.64 190.32 192.69 0.000178 0.97 65.69 96.96 0.171823 THE PARKWAY Bridge1807 Regional 63.4 188.95 192.35 190.32 192.39 0.00019 0.94 109.48 84.58 0.171800 Regional 63.3 188.68 192.33 192.38 0.000605 1.64 130.29 321.45 0.281765 Regional 63.3 188.82 191.98 191.09 192.32 0.002755 3.18 50.67 402.44 0.581705 Regional 63.3 188.34 191.98 191.32 192.13 0.001773 2.33 73.3 602.03 0.411645 Regional 63.3 188.32 191.67 191.37 191.97 0.003443 3.04 48.12 519.59 0.561585 Regional 63.3 188.29 191.7 191.04 191.8 0.001229 2.18 106.11 406.59 0.381565 Regional 62.6 188.28 191.73 191.76 0.000598 1.53 166.87 274.23 0.271552 Regional 62.6 188.2 191.75 189.52 191.75 0.000029 0.33 228.16 354.96 0.081543 CRAWFORD Culvert1534 Regional 62.6 188.2 191.53 189.52 191.54 0.000045 0.39 171.51 215.9 0.11527 Regional 62.5 188.47 191.52 191.54 0.000309 1 161.94 315.94 0.191346 Regional 62.5 188.22 191.44 190.69 191.48 0.00056 1.35 85.57 99.25 0.241322 Regional 62.5 188.08 191.05 191.32 0.002439 2.52 30.92 18.79 0.511305 Regional 61.9 188.2 191.08 191.25 0.001602 2.3 65.58 156.95 0.431187 Regional 61.9 187.54 190.89 191.05 0.0018 2.22 50.59 85.2 0.421025 Regional 61.9 187.44 190.71 190.81 0.001142 1.78 62.22 70.18 0.33865 Regional 61.9 187.42 190.56 190.63 0.000995 1.61 63.19 45.26 0.31725 Regional 62.5 187.39 190.39 190.49 0.000966 1.5 49.91 31.96 0.32543 Regional 62.5 187.33 190.37 190.39 0.000238 0.89 140.82 193.79 0.17384 Regional 62.5 186.93 190.34 190.35 0.000173 0.75 184.07 394.76 0.13223 Regional 72.3 186.6 190.3 190.31 0.000324 1.03 179.75 295.05 0.1883 Regional 72.3 186.29 190.27 190.29 0.00014 0.79 150.21 128.33 0.1355 Regional 72.3 186.6 190.27 190.2 190.28 0.000082 0.59 224.53 146.6 0.142.5 JOHNSTON Bridge30 Regional 72.3 186.3 189.13 188.79 189.15 0.000349 1.03 114.9 80.66 0.227 Regional 72.3 186.37 188.14 188.14 188.92 0.012406 3.91 18.47 11.83 124 Regional 72.3 186.3 187.26 187.72 188.79 0.045054 5.47 13.22 14.5 1.8321 Regional 72.3 186.23 186.95 187.43 188.61 0.06734 5.7 12.68 18.1 2.1718 Regional 73.5 186.16 186.81 187.25 188.37 0.072057 5.54 13.27 20.96 2.22

TABLE D-8HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 1: No washouts at former CNR, and no blockage of Erskine Avenue storm inletLOWER SPILL Model (south of former CNR) ‐ CASE 1CNR Spill ‐ Case 1River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude #Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)460 Regional 1.28 191.18 191.33 191.27 191.33 0.001016 0.39 4.55 180.31 0.36450 Regional 1.28 191.18 191.29 191.31 0.003373 0.56 2.77 141.11 0.61400 Regional 1.28 191.00 191.22 191.22 0.000569 0.32 9.56 73.59 0.27350 Regional 1.28 191.03 191.05 191.04 191.08 0.501954 1.9 2.07 85.23 5.44300 Regional 2.63 190.59 191.04 191.04 0.00011 0.21 20.83 148.68 0.13250 Regional 4.91 190.76 190.91 190.91 190.97 0.010571 1.37 17.78 204.24 1.18200 Regional 4.91 190.35 190.71 190.49 190.71 0.000635 0.48 35.34 222.82 0.32150 Regional 4.91 190.34 190.56 190.60 0.006202 1.06 14.25 131.15 0.9100 Regional 7.56 189.98 190.37 190.28 190.40 0.001925 0.82 11.95 64.44 0.55

TABLE D-9HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 1: No washouts at former CNR, and no blockage of Erskine Avenue storm inletEXAMINER DITCH Model ‐ CASE 1River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude #Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)2050 Regional 12.1 192.90 194.88 193.97 194.91 0.000697 0.84 14.39 107.69 0.221978 Regional 11.8 192.69 194.79 193.52 194.85 0.000566 1.11 10.63 86.67 0.251974 Culvert1964 Regional 11.8 192.60 193.58 193.49 193.91 0.009347 2.56 4.61 17.15 0.861950 Regional 11.8 192.46 193.54 193.63 0.003996 1.82 13.13 29.12 0.571882 Regional 11.8 191.85 193.19 193.19 193.32 0.005132 1.92 11.89 47.21 0.611850 Regional 11.8 191.65 193.04 192.72 193.08 0.001195 1.01 18.83 42.53 0.311800 Regional 11.8 191.35 193.01 193.03 0.000541 0.78 26.46 53.37 0.221777 Regional 11.8 191.22 193.02 192.37 193.02 0.000172 0.21 61.94 173.89 0.11770 Culvert1763 Regional 11.8 191.19 193.02 193.02 0.000015 0.06 247.66 904.66 0.031700 Regional 11.8 191.24 193.02 193.02 0.000025 0.12 195.38 709.85 0.041610 Regional 11.8 191.12 193.01 193.01 0.00008 0.3 140.01 512.37 0.081553 Regional 11.8 191.26 192.92 192.97 0.001269 1.08 13.75 24.7 0.321500 Regional 11.8 191.06 192.91 192.93 0.000335 0.73 20.37 20.48 0.181458 Regional 9.6 190.80 192.84 191.58 192.90 0.000523 1.05 9.16 329.83 0.231442 Culvert1428 Regional 9.6 190.48 192.18 192.29 0.001439 1.47 6.51 73.98 0.371427 Lat Struct1405 Regional 7.87 190.45 192.15 192.22 0.00122 1.27 8.5 10.29 0.331327 Regional 7.87 190.35 191.95 192.03 0.001563 1.35 7.49 9.12 0.371250 Regional 7.87 190.01 191.77 191.87 0.002375 1.43 6.06 5.3 0.381194 Regional 2.94 190.28 191.73 191.00 191.76 0.000879 0.83 4.64 33.72 0.241123 Regional 2.94 190.35 191.61 191.66 0.002164 1.1 3.65 5.93 0.351050 Regional 2.94 190.67 191.29 191.17 191.37 0.009405 1.22 2.4 6.55 0.65

TABLE D-10HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 1: No washouts at former CNR, and no blockage of Erskine Avenue storm inletEXAMINER DITCH WEST SPILL model ‐ CASE 1Spill from Examiner Ditch southwestward along the north side of former CNR track ‐ Case 1River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaTop Froude #Width Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)871 Regional 7.48 191.33 192.04 191.55 192.04 0.00003 0.10 88.99 225.0 0.04826 Regional 7.48 191.59 192.01 192.03 0.00313 0.73 11.65 116.4 0.42781 Regional 7.48 191.59 191.99 192.00 0.00028 0.23 29.60 104.6 0.13745 Regional 7.48 191.59 191.89 191.89 191.96 0.01717 1.12 6.46 49.0 0.88676 Regional 7.48 191.17 191.70 191.33 191.71 0.00008 0.15 51.34 127.7 0.07626 Regional 3.40 191.20 191.70 191.70 0.00006 0.10 33.80 123.4 0.06606 Regional 3.40 191.17 191.70 191.70 0.00002 0.07 50.88 127.4 0.03578 Regional 3.40 191.30 191.70 191.70 0.00009 0.11 31.04 146.0 0.07508 Regional 3.40 191.15 191.70 191.70 0.00003 0.07 50.04 181.5 0.04448 Regional 3.40 191.00 191.70 191.70 0.00002 0.06 56.85 194.5 0.04294 Regional 3.40 191.36 191.69 191.69 0.00009 0.08 42.83 259.8 0.06281 Regional 3.40 191.28 191.69 191.69 0.00003 0.06 63.21 342.8 0.04266 Regional 3.40 190.22 191.69 191.69 0.00020 0.21 16.30 46.4 0.11222 Regional 3.40 190.00 191.69 191.69 0.00002 0.07 49.79 125.6 0.03172 Regional 3.40 190.50 191.69 191.69 0.00000 0.04 75.91 163.0 0.02159 Regional 3.40 190.00 191.69 191.69 0.00001 0.05 63.39 176.8 0.02152 Regional 3.40 191.49 191.67 191.69 0.00080 0.56 6.84 74.7 0.5142 Regional 3.40 191.49 191.63 191.63 191.67 0.00311 0.87 4.19 61.2 0.92135 Regional 3.40 191.00 191.15 191.24 191.56 0.32517 2.85 1.19 16.3 3.36122 Regional 3.40 190.28 190.91 190.91 191.07 0.01870 1.78 1.91 6.1 1.0192 Regional 3.40 190.00 190.81 190.48 190.83 0.00126 0.55 6.14 15.1 0.2850 Regional 3.40 190.00 190.54 190.54 190.68 0.01948 1.65 2.06 7.6 1.01

TABLE D-11HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 4: Same as Case 1 but with twin 2.0-m CPR culverts replacedTwin 2.0‐m CPR culverts east of The Parkway replaecd by single 1.0‐m CSP culvertMAIN BRANCH Model ‐ CASE 4River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaTop Froude #Width Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)3645 Regional 37.4 199.17 200.38 200.38 200.77 0.013833 2.79 13.4 16.8 1.003554 Regional 47.4 197.06 198.78 198.83 199.35 0.01424 3.36 14.1 14.0 1.073390 Regional 55.2 194.79 196.72 197.06 197.42 0.009666 4.23 18.4 26.0 0.993165 Regional 55.2 193.68 196.24 195.89 196.29 0.000905 1.47 69.7 241.8 0.313073 Regional 55.2 193.29 196.15 195.31 196.20 0.001187 1.36 74.7 145.0 0.263068 Regional 55.2 193.29 196.15 195.81 196.19 0.000343 1.36 121.3 215.2 0.263047 Bridge3026 Regional 55.2 193.23 195.80 195.80 196.02 0.001255 2.46 57.8 150.8 0.493025 Regional 55.2 193.23 195.48 195.27 195.56 0.002106 1.63 55.0 115.7 0.353023 Regional 55.2 193.23 195.49 195.25 195.55 0.001768 1.50 55.1 115.9 0.323009 Regional 55.2 193.23 195.44 195.25 195.53 0.002101 1.62 51.2 139.1 0.352999 Regional 55.2 193.23 195.40 195.25 195.50 0.00249 1.75 47.5 127.7 0.382993 Regional 55.2 193.23 195.37 195.25 195.48 0.002846 1.86 44.8 105.2 0.412986 Regional 55.2 193.23 195.25 195.25 195.45 0.00487 2.37 35.0 90.5 0.542969 Regional 55.2 193.08 195.33 194.89 195.35 0.000493 0.85 97.1 176.9 0.182961 Regional 55.2 193.08 195.32 195.35 0.000556 1.04 95.3 152.2 0.222947 Regional 55.2 192.90 195.32 195.34 0.000525 0.92 103.9 200.8 0.192940 Regional 55.2 192.90 195.32 194.58 195.33 0.000463 0.86 114.6 227.8 0.182939 Regional 55.2 192.90 195.31 194.58 195.33 0.000538 0.93 103.1 202.6 0.192917 Regional 55.2 192.90 195.30 194.59 195.32 0.000565 0.95 111.2 227.3 0.192889 Regional 55.2 192.90 195.29 195.31 0.000449 0.84 131.1 280.4 0.172883 Regional 55.2 192.25 195.29 194.20 195.30 0.000319 0.82 128.5 245.3 0.162703 Regional 55.2 192.01 195.26 195.27 0.000134 0.62 135.2 250.1 0.122662 Regional 43.1 191.95 195.25 195.26 0.000187 0.80 102.8 110.6 0.152512 Regional 43.1 191.50 195.24 195.25 0.000057 0.50 176.2 151.7 0.082506 Regional 44.1 191.20 195.23 195.24 0.000111 0.72 123.7 118.8 0.122332 Regional 60.8 190.60 195.22 195.23 0.000083 0.63 176.8 132.3 0.102320 Regional 60.8 191.30 194.90 193.09 195.10 0.000999 1.97 30.8 48.6 0.332310 CPR Culvert2300 Regional 60.8 191.30 193.07 193.07 193.90 0.011184 4.04 15.0 45.3 0.992275 Regional 60.8 189.69 192.92 191.93 193.16 0.001708 2.44 33.8 19.5 0.452148 Regional 60.8 189.60 192.91 191.64 192.97 0.000673 1.21 91.3 146.1 0.262031 Regional 60.8 189.50 192.67 192.83 0.002032 1.83 33.8 21.4 0.431845 Regional 63.4 188.81 192.66 192.69 0.000254 1.03 182.5 451.6 0.181839 Regional 63.4 188.95 192.64 190.32 192.69 0.000178 0.97 65.7 97.0 0.171823 Bridge1807 Regional 63.4 188.95 192.35 190.32 192.39 0.00019 0.94 109.5 84.6 0.171800 Regional 63.3 188.68 192.33 192.38 0.000605 1.64 130.3 321.5 0.281765 Regional 63.3 188.82 191.98 191.09 192.32 0.002755 3.18 50.7 402.4 0.581705 Regional 63.3 188.34 191.98 191.32 192.13 0.001773 2.33 73.3 602.0 0.411645 Regional 63.3 188.32 191.67 191.37 191.97 0.003443 3.04 48.1 519.6 0.561585 Regional 63.3 188.29 191.70 191.04 191.80 0.001229 2.18 106.1 406.6 0.381565 Regional 62.6 188.28 191.73 191.76 0.000598 1.53 166.9 274.2 0.271552 Regional 62.6 188.20 191.75 189.52 191.75 0.000029 0.33 228.2 355.0 0.081543 Culvert1534 Regional 62.6 188.20 191.53 189.52 191.54 0.000045 0.39 171.5 215.9 0.101527 Regional 62.5 188.47 191.52 191.54 0.000309 1.00 161.9 315.9 0.191346 Regional 62.5 188.22 191.44 190.69 191.48 0.00056 1.35 85.6 99.3 0.241322 Regional 62.5 188.08 191.05 191.32 0.002439 2.52 30.9 18.8 0.511305 Regional 61.9 188.20 191.08 191.25 0.001602 2.30 65.6 157.0 0.431187 Regional 61.9 187.54 190.89 191.05 0.0018 2.22 50.6 85.2 0.421025 Regional 61.9 187.44 190.71 190.81 0.001142 1.78 62.2 70.2 0.33865 Regional 61.9 187.42 190.56 190.63 0.000995 1.61 63.2 45.3 0.31725 Regional 62.5 187.39 190.39 190.49 0.000966 1.50 49.9 32.0 0.32543 Regional 62.5 187.33 190.37 190.39 0.000238 0.89 140.8 193.8 0.17384 Regional 62.5 186.93 190.34 190.35 0.000173 0.75 184.1 394.8 0.13223 Regional 72.3 186.60 190.30 190.31 0.000324 1.03 179.8 295.1 0.1883 Regional 72.3 186.29 190.27 190.29 0.00014 0.79 150.2 128.3 0.1355 Regional 72.3 186.60 190.27 190.20 190.28 0.000082 0.59 224.5 146.6 0.1042.5 Bridge30 Regional 72.3 186.30 189.13 188.79 189.15 0.000349 1.03 114.9 80.7 0.2027 Regional 72.3 186.37 188.14 188.14 188.92 0.012406 3.91 18.5 11.8 1.0024 Regional 72.3 186.30 187.26 187.72 188.79 0.045054 5.47 13.2 14.5 1.8321 Regional 72.3 186.23 186.95 187.43 188.61 0.06734 5.70 12.7 18.1 2.1718 Regional 73.5 186.16 186.81 187.25 188.37 0.072057 5.54 13.3 21.0 2.22

TABLE D-12HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 4: Same as Case 1 but with twin 2.0-m CPR culverts replacedTwin 2.0‐m CPR culverts east of The Parkway replaecd by single 1.0‐m CSP culvertLOWER SPILL Model (south of former CNR) ‐ CASE 4CNR Spill ‐ Case 4River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude # Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)460 Regional 0.58 191.18 191.29 191.24 191.29 0.000735 0.26 2.7 140.3 0.29450 Regional 0.58 191.18 191.24 191.24 191.26 0.010915 0.59 1.1 103.1 0.97400 Regional 0.58 191.00 191.15 191.16 0.000498 0.24 5.9 65.6 0.24350 Regional 0.58 191.03 191.02 191.02 191.04 0.692881 0.9 60.4 0300 Regional 2.50 190.59 190.96 190.79 190.97 0.000236 0.28 14.5 120.9 0.19250 Regional 2.35 190.76 190.87 190.87 190.90 0.011272 1.07 10.5 193.0 1.14200 Regional 2.35 190.35 190.62 190.36 190.62 0.00055 0.35 21.6 148.7 0.28150 Regional 2.35 190.34 190.46 190.36 190.50 0.016824 1.15 6.2 78.2 1.34100 Regional 4.68 189.98 190.37 190.23 190.38 0.000738 0.5 12.0 64.4 0.34

TABLE D-13HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 4: Same as Case 1 but with twin 2.0-m CPR culverts replacedTwin 2.0‐m CPR culverts east of The Parkway replaecd by single 1.0‐m CSP culvertEXAMINER DITCH Model ‐ CASE 4Examiner Ditch ‐ Case 4River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow AreaTopWidthFroude # Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)2050 Regional 12.1 192.9 196.00 193.97 196.00 0.00 0.06 263.98 133.93 0.011978 Regional 5.3 192.69 196.00 193.38 196.00 0.00 0.03 207.91 104.95 0.011974 Culvert1964 Regional 5.3 192.6 193.51 193.51 193.96 0.01 2.96 1.79 15.58 11950 Regional 5.3 192.46 193.33 193.09 193.37 0.00 1.2 8.08 19.81 0.421882 Regional 5.3 191.85 192.80 192.80 193.04 0.01 2.17 2.64 7.71 0.891850 Regional 5.3 191.65 192.78 192.49 192.81 0.00 0.89 9.21 29.29 0.321800 Regional 5.3 191.35 192.75 192.77 0.00 0.61 14.42 37.41 0.191777 Regional 5.3 191.22 192.74 191.90 192.74 0.00 0.4 15.05 147.31 0.351770 Culvert1763 Regional 5.3 191.19 192.63 192.71 0.00 1.29 4.12 418.32 0.341700 Regional 5.3 191.24 192.61 192.61 0.00 0.27 20.24 79.23 0.141610 Regional 5.3 191.12 192.53 192.56 0.00 0.8 7.3 48.03 0.271553 Regional 5.3 191.26 192.39 192.45 0.00 1.08 4.92 7.22 0.421500 Regional 5.3 191.06 192.39 192.40 0.00 0.57 11.12 16.22 0.171458 Regional 5.1 190.8 192.35 191.31 192.38 0.00 0.73 6.96 86.29 0.191442 Culvert1428 Regional 5.1 190.48 192.16 192.19 0.00 0.79 6.46 73.76 0.21427 Lat Struct1405 Regional 5.1 190.45 192.15 192.18 0.00 0.82 8.49 10.29 0.211327 Regional 5.1 190.35 192.09 192.11 0.00 0.78 8.86 10.69 0.21250 Regional 5.2 190.01 192.05 192.07 0.00 0.77 8.35 11.51 0.191194 Regional 5.2 190.28 191.96 191.24 192.02 0.00 1.2 6.9 56.15 0.311123 Regional 5.2 190.35 191.73 191.85 0.00 1.7 4.45 7.43 0.511050 Regional 3.3 190.67 191.49 191.20 191.53 0.00 0.85 3.87 8.15 0.39

TABLE D-14HEC-RAS RESULTS for REGIONAL STORM EVENTModel Scenario Case 4: Same as Case 1 but with twin 2.0-m CPR culverts replacedTwin 2.0‐m CPR culverts east of The Parkway replaecd by single 1.0‐m CSP culvertEXAMINER DITCH WEST SPILL model ‐ CASE 4Spill from Examiner Ditch southwestward along the north side of former CNR track ‐ Case 3River Sta Profile Q Total Min Ch El W.S. Elev Crit W.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude #Chl(m3/s) (m) (m) (m) (m) (m/m) (m/s) (m2) (m)871 Regional 3.76 191.33 191.94 191.51 191.94 0.000013 0.06 67.52 186.38 0.03826 Regional 3.76 191.59 191.92 191.93 0.001764 0.47 7.87 32.68 0.3781 Regional 3.76 191.59 191.91 191.91 0.000227 0.17 20.89 97.19 0.11745 Regional 3.76 191.59 191.82 191.82 191.88 0.015907 0.9 3.73 32.33 0.81676 Regional 3.76 191.17 191.69 191.29 191.69 0.000023 0.08 49.52 126.65 0.04626 Regional 2.94 191.20 191.69 191.69 0.000052 0.09 32.24 121 0.05606 Regional 2.94 191.17 191.69 191.69 0.000014 0.06 49.26 126.51 0.03578 Regional 2.94 191.30 191.69 191.69 0.000077 0.1 29.26 140.89 0.06508 Regional 2.94 191.15 191.68 191.68 0.000027 0.06 47.87 179.33 0.04448 Regional 2.94 191.00 191.68 191.68 0.000019 0.05 54.56 193.91 0.03294 Regional 2.94 191.36 191.68 191.68 0.000076 0.07 39.95 250.13 0.06281 Regional 2.94 191.28 191.68 191.68 0.000028 0.05 59.36 339.15 0.04266 Regional 2.94 190.22 191.68 191.68 0.000165 0.19 15.81 46.05 0.1222 Regional 2.94 190.00 191.68 191.68 0.000012 0.06 48.46 123.52 0.03172 Regional 2.94 190.50 191.68 191.68 0.000003 0.03 74.19 161.05 0.01159 Regional 2.94 190.00 191.68 191.68 0.000006 0.05 61.54 172.64 0.02152 Regional 2.94 191.49 191.66 191.68 0.000799 0.53 6.16 71.5 0.49142 Regional 2.94 191.49 191.63 191.63 191.66 0.003098 0.83 3.78 58.77 0.91135 Regional 2.94 191.00 191.14 191.22 191.55 0.355994 2.84 1.03 15.17 3.48122 Regional 2.94 190.28 190.87 190.87 191.02 0.019146 1.73 1.7 5.75 1.0292 Regional 2.94 190.00 190.77 190.46 190.79 0.001232 0.53 5.56 14.41 0.2750 Regional 2.94 190.00 190.51 190.51 190.64 0.019898 1.6 1.83 7.21 1.02