Flood Mitigation Case Study Coralville, Iowa

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Flood Mitigation Case Study Coralville, Iowa

Flood Mitigation Case Study

Coralville, Iowa

Dan Holderness, PE

Coralville City Engineer

Teresa Stadelmann, PE

HR Green


§¨¦ 29 §¨¦ 380

Omaha

§¨¦ 80

Des Moines

§¨¦ 35

Flood Mitigation Case StudyCoralville, Iowa

Cedar Rapids

Coralville


Clear Creek

Biscuit Creek

Flood Mitigation Case StudyCoralville, Iowa

Coralville Reservoir

Iowa River


The Flood of 2008

Flood Mitigation Case StudyCoralville, Iowa

• June 4 th

▫ US Army Corps of Engineers warns water could go over

Coralville Reservoir spillway

▫ Sandbagging begins and continues for 10 days

• June 5 th

▫ Water begins flooding in Coralville

• June 8 th

Iowa River surpasses flood stage

• June 9 th

Flood roughly equal to 1993 predicted

• June 10 th

▫ Due to continuing rainfall, flood larger than 1993 predicted

Coralville Reservoir goes over spillway for second time in

50-year history, flood gates opened wide


Flood Mitigation Case StudyCoralville, Iowa


The Flood of 2008

Flood Mitigation Case StudyCoralville, Iowa

• June 11 th

▫ Peak flow projection raised to 33,000 cfs

▫ Storms predicted in late evening and early morning hours

• June 12 th

▫ Rain begins shortly after midnight

▫ Edgewater Drive neighborhood evacuated

▫ Corps reports significant rainfall in Iowa River basin from

overnight storm and revises projected flood peak to 40,000 cfs

▫ Critical infrastructure in jeopardy

Coralville Wastewater Department staff works in several feet of

floodwater to remove control panels and other items from four

storm water pump stations and two sanitary lift stations, as well

as traffic signal controllers

▫ Water breaches CRANDIC Railroad embankment, flooding

Highway 6 and the Coralville Strip


Iowa River overtops

CRANDIC embankment

Flood Mitigation Case StudyCoralville, Iowa


June 13th

Flood Mitigation Case StudyCoralville, Iowa


June 13th

Flood Mitigation Case StudyCoralville, Iowa


The Flood of 2008

• June 13 th

▫ 4 th Avenue neighborhood evacuated

▫ Sandbag dike breaks at Edgewater

Drive & Quarry Road

▫ 1993 Iowa River record elevation

surpassed

▫ Interstate 380 closed

• June 14 th

Coralville Reservoir passes record

elevation

▫ Sandbagging efforts continue

▫ Additional storms and tornado warning

• June 15 th

Iowa River crests earlier than

expected, maximum flow 41,000 cfs

Flood Mitigation Case StudyCoralville, Iowa


The Flood of 2008

• June 17 th

▫ Interstate 380 reopens

• June 21 st

▫ US Highway 6 reopens, one lane each

direction

• June 23 rd

▫ 1 st Avenue and 4 th Street remain closed

• June 24 th

▫ Water stops going over Coralville spillway

• July 7 th

Iowa River falls below flood stage

Flood Mitigation Case StudyCoralville, Iowa


Flood Aftermath

Flood Mitigation Case StudyCoralville, Iowa

• Impacted

▫ 273 acres flooded

▫ 420 Households

▫ 200 Businesses

• Damages

▫ $21M commercial

▫ $4M residential

▫ $7M public infrastructure


Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


First Steps

Flood Mitigation Case StudyCoralville, Iowa

• City immediately began both recovery work and planning

for the future

▫ Coordination with neighboring communities

▫ Buyouts along Edgewater Drive

• September 2008 - two consultants under contract to

complete flood mitigation studies

Flood protection along Iowa River / CRANDIC Railroad alignment

▫ Storm sewer system, pump stations and remainder of flood

protection

• November 2008 – flood mitigation studies completed

▫ Vital information obtained to complete funding applications


Flood

Study Area

Flood Mitigation Case StudyCoralville, Iowa


US Hwy 6

Flood Mitigation Case StudyCoralville, Iowa

1 st Avenue

1 st Avenue Bridge

over Clear Creek


Iowa Interstate

Railroad

Flood Mitigation Case StudyCoralville, Iowa

CRANDIC

Railroad


4 th Avenue

Neighborhood

McGurk Meyers PS

Iowa Land Lodge PS

Flood Mitigation Case StudyCoralville, Iowa

Edgewater Drive

Neighborhood

Taco Bell PS

Jiffy Lube PS


Flood Mitigation Study Goals

Flood Mitigation Case StudyCoralville, Iowa

• Evaluate existing storm water and flood protection

system against the June 2008 flood plus one foot of

freeboard and identify areas for improvement in the flood

protection

• Identify and evaluate alternatives to withstand a similar

flood

• Develop opinion of capital costs for the improvements

• Develop recommendations to prioritize the capital

improvements


Flood Mitigation Case StudyCoralville, Iowa

Mitigation Study Recommendations

• Comprehensive flood protection

▫ Repair existing storm water pump stations

▫ Backflow prevention

▫ Mixture of berms, flood walls, and removable flood walls specific

to each location and future development / redevelopment plans

▫ Additional storm water pump stations to handle interior drainage

• Build on the existing system

▫ Prevent backflow for entire storm sewer system

▫ Raise protection level of existing pump stations and flood walls

▫ Close gaps in protection

• Protect critical infrastructure

▫ Transportation corridors

▫ Sanitary lift stations

▫ Electrical substations and switch gear

• Protect the lowest / most flood prone areas first


Flood Mitigation Case StudyCoralville, Iowa

Mitigation Study Recommendations

E

C

D

B

A

Flood Protection Regions

▫ Each region can be built

independently and provide flood

protection for that region alone

▫ Allows for smaller projects to be

completed as funding becomes

available


Flood Mitigation Case StudyCoralville, Iowa


Pump Station

Flood Mitigation Case StudyCoralville, Iowa


42 document discharges to the

Iowa River and its tributaries

Storm Sewer Outfall

Pump Station

Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


Incorporating Green Space

Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa


Flood Mitigation Case StudyCoralville, Iowa

Pump Station 1

Pump Station 2


Pump Station 9

Pump Station 3

Pump Station 10

Flood Mitigation Case StudyCoralville, Iowa

Pump Station 4


Flood Mitigation Case StudyCoralville, Iowa


Funding

Flood Mitigation Case StudyCoralville, Iowa

Mitigation studies completed with City funds

• Several grant programs pursued for design/construction

▫ HMGP, CDBG, EDA, I-JOBS

• Grants awarded

▫ I-JOBS $27.1 Million Berms, walls, pump stations, 1st Avenue, Bridge

▫ EDA $ 7.1 Million Flood protection along CRANDIC

▫ CDBG $ 3.1 Million Flood protection along CRANDIC

▫ CDBG $ 600,000 Storm sewer backflow prevention

▫ I-JOBS II $ 3.6 Million Clear & Biscuit Creek flood protection

▫ CDBG $10.0 Million Pump stations, 4 th Ave storm sewer


Progress to Date

Flood Mitigation Case StudyCoralville, Iowa

• Projects Completed

▫ Restored all existing pump stations to pre-flood operation Summer 2009

• Under Construction

▫ Storm sewer backflow prevention

▫ 1 st Avenue Bridge over Clear Creek with removable floodwall closures

Iowa River Landing Wetland Park and flood walls (Region A)

▫ 1 st Avenue Corridor Flood Protection, including four new pump stations

along the Iowa River and flood control berms (Regions A and C)

▫ 1 st Avenue Reconstruction


2010-11 Construction

Flood Mitigation Case StudyCoralville, Iowa


2010-11 Construction

Flood Mitigation Case StudyCoralville, Iowa


2010-11 Construction

Pump Station #4

Flood Mitigation Case StudyCoralville, Iowa


2010-11 Construction

Flood Mitigation Case StudyCoralville, Iowa


2010-11 Construction

Flood Mitigation Case StudyCoralville, Iowa


Projects in Design

Region B

I-JOBS II

CDBG

Pump Stations

Iowa River /

CRANDIC Alignment

Flood Mitigation Case StudyCoralville, Iowa

• Region B Flood Protection

Iowa River / CRANDIC

Alignment Flood Protection

• I-JOBS II Flood Protection

• Clear Creek and Biscuit Creek

• CDBG Storm Water Pump

Stations

• Two new pump stations

• Upgrades to four existing pump

stations

• 4th Avenue storm sewer system


Flood Mitigation Case StudyCoralville, Iowa


Success Story

Flood Mitigation Case StudyCoralville, Iowa

• Coordination and quick response within community

• Data collection during the flood

• Coordination with neighboring Iowa City and the

University of Iowa

▫ Updated Iowa River and Clear Creek HEC-RAS models

• Coordination with consultants during and after flood

• Aggressive pursuit of grant funding opportunities

• Commitment to an aggressive schedule

• Because of the work completed to date, redevelopment

is occurring in many areas that were flooded

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