Appendix L - Federal Emergency Management Agency

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Appendix LWhen digitizing maps, it is important to measure how well the registration control points line up to themap. The measurement of fit is sometimes called the Root Mean Squared Error (RMSE). The RMSEvalue represents the amount of error between new and original coordinate locations calculated by thetransformation process. The RMSE should be minimized, and the spatial features on the maps must be asclose to their true location on the base map as possible.• Digitized linework must be collected at a reasonably fine line weight.• Only simple line strings or simple linear elements may be used for all linework.• Line features must be continuous (no dashes, dots, patterns, or hatching).L.4.6.5 Vertex spacing [October 2011]Vertices along digitized or generated boundaries should be spaced such that, on average, no vertices existwithin a 10-foot ground sample distance from one another. Exceptions may occur in areas of fingerflooding to ensure the flood zone is properly delineated. Exceptions should be documented in themetadata. Floodplain Boundary Standard (FBS) requirements must be met, as outlined in the FEMARevised Procedure Memorandum No. 38 – Implementation of Floodplain Boundary Standard (Section 7.0of MHIP 1.0) dated October 17, 2007, as well as the Floodplain Standards Audit Procedures, version 2.0dated October 17, 2007.If boundaries are delineated on highly accurate topographic data, denser vertex spacing may be required.Wherever possible, vertices should be thinned to meet the average 10-foot ground spacing, while allowingfor small localized areas of denser spacing.L.4.6.6 PGDB Standards [October 2011]Personal geodatabases must be submitted in Esri Personal Geodatabase version 9.3 format or higher, andthe version must be accurately documented in the FIRM Database metadata file.All spatial FIRM layers should exist within one feature dataset. The feature dataset assists in the creationof topology layers when necessary and allows for the expansion of topology rules in the future. Thesingle FIRM Database feature dataset must be named “FIRM_Spatial_Layers” in order to aid in theautomated loading of spatial layers into the DVT automated checking tool and the NFHL.Non-spatial tables shall exist outside of the FIRM_Spatial_Layers feature dataset, but inside the PGDB.L.4.6.7 XY Tolerance for Geodatabases [October 2011]The XY tolerance for a feature dataset created in a geodatabase to store FIRM data must be 0.25 feet(0.0762 meters).L.4.6.8 Coincident Features [October 2011]Coincident features are those that share the same location or boundary, such as a flood zone boundary anda floodwall. These coincident features must be superimposed, vertex (shape point) for vertex, within thefiles. If they are not located properly, it could appear that the flood zone ends before the wall, leaving astrip of land on the waterside of the floodwall that is not in the flood zone. A lack of alignment can causeproblems with digital files.Guidelines and Standards forFlood Risk Analysis and Mapping Page L-24 Section L.4 Preliminary and Final Databases
Appendix LIn the FIRM Database, flood hazard data are contained in both area and line features: S_Fld_Haz_Ar andS_Fld_Haz_Ln. For this data theme, two layers are defined because they have attributes that apply to theentire area and attributes that apply to portions of the boundaries of these areas. However, the spatialelements that make up these features must be identical. All elements in the S_Fld_Haz_Ln table mustmatch the boundaries of the elements in the S_Fld_Haz_Ar table, within the specified database tolerance.L.4.6.9 Feature Precision [October 2011]The position of horizontal control features of the FIRM products will be based on published standards.The assigned mapping partner shall not re-digitize these control features, but shall use the exactcoordinates in the published standards. Candidate sources of control points include:• U.S. Geological Survey 7.5-minute series quadrangle map corner coordinates• Coordinate grids• Public Land Survey Systems (PLSS)L.4.6.10 Data Compilation [October 2011]Existing digital data may affect the choice of scale for data compilation. If base mapping is available at ascale greater than 1″ = 400′ (e.g. 1″ = 200′) the assigned mapping partner may choose to compile anddigitize the revised data developed during the flood risk project at the base map scale.In general, the most accurate data source available must be relied upon to reference other featurescompiled onto the map. This may mean that, in limited circumstances, floodplain boundary delineationsmade on very high-resolution topographic maps may appear slightly misplaced on a less accurate basemap. However, if the base map meets FEMA standards, these differences should be very small. If thispolicy creates significant visual problems with the floodplain boundary delineations on the base mapselected, the mapping partner shall resolve the issue with the FEMA Project Officer.Likewise, when high-accuracy data are collected for a flood risk project, it is FEMA’s goal to maintainthe accuracy of those data. For example, cross-section line features must correspond as closely aspossible to the actual field survey locations. Often, the mapping partner must graphically extend orreshape that end of a cross section for satisfactory cartographic display.L.4.6.11 Relationship of Base Map to Flood Hazard Data [October 2011]Base map features are physical features like roads, railroads, rivers, lakes, orthophotography and politicalboundaries, that map users may rely on to locate an area of interest on the FIRM. For the graphicstandards for base map features, refer to Appendix K of the Guidelines and Standards. Table L-2 lists thebase map features and lookup tables, and whether or not they are required or required if applicable.Flood hazard data include flood insurance risk zones, Base Flood Elevations (BFEs), cross-sectionlocations, and hydraulic structures on a FIRM that depict the results of flood hazard analyses. Somephysical features, such as surface water features and hydraulic structures, are also used during floodhazard analyses and may be grouped in either category.Guidelines and Standards forFlood Risk Analysis and Mapping Page L-25 Section L.4 Preliminary and Final Databases
Page 1 and 2: Guidelines and Standards for FloodR
Page 3 and 4: Appendix LDate Affected Section(s)
Page 17 and 18: Appendix LTable of ContentsL.1. Flo
Page 19 and 20: Appendix LL.8.17 Table: S_Levee [Oc
Page 21 and 22: Appendix LAppendix LDigital Data an
Page 23: Appendix LFIRM Table NameTableTypeT
Page 26 and 27: Appendix LTable L-2. Mapping Partne
Page 28 and 29: Appendix LFIR M Table NameAcquireB
Page 30: Appendix LAppendix are identified i
Page 33 and 34: Appendix Lfiles for lookup tables.
Page 35 and 36: Appendix LWhen possible, tables req
Page 37 and 38: Appendix L• Area spatial features
Page 39: Appendix LTopologyFilename(*_TOPOLO
Page 43 and 44: Appendix Lfield length indicates th
Page 45 and 46: Appendix LL.4.8 Deliverables [Octob
Page 47 and 48: Appendix LL.5. Database Table Struc
Page 49 and 50: Appendix LL.7. Metadata Example for
Page 51 and 52: Appendix LFAN_VEL_MX A Alluvial Fan
Page 53 and 54: Appendix LTable: S_Base_Index [Octo
Page 55 and 56: Appendix Lboundary. Each BFE is rep
Page 57 and 58: Appendix LTable: S_CBRS [October 20
Page 59 and 60: Appendix LTIME_UNIT A Recording Int
Page 61 and 62: Appendix LL.8.6 Table: S_Cst_Tsct_L
Page 63 and 64: Appendix LCON_PD A Controlling Wave
Page 65 and 66: Appendix LTable: S_Cst_Tsct_Ln [Oct
Page 67 and 68: Appendix LL.8.7 Table: S_Datum_Conv
Page 69 and 70: Appendix LL.8.8 Table: S_FIRM_Pan [
Page 71 and 72: Appendix LL.8.9 Table: S_Fld_Haz_Ar
Page 73 and 74: Appendix LTable: S_Fld_Haz_Ar [Octo
Page 75 and 76: Appendix LL.8.11 Table: S_Gage [Oct
Page 77 and 78: Appendix LL.8.12 Table: S_Gen_Struc
Page 79 and 80: Appendix LL.8.13 Table: S_HWM [Octo
Page 81 and 82: Appendix LL.8.14 Table: S_Hydro_Rea
Page 83 and 84: Appendix LL.8.16 Table: S_Label_Pt
Page 85 and 86: Appendix LL.8.17 Table: S_Levee [Oc
Page 87 and 88: Appendix LTable: S_Levee [October 2
Page 89 and 90: Appendix LL.8.19 Table: S_LOMR [Oct
Page 91 and 92:
Appendix LL.8.20 Table: S_Nodes [Oc
Page 93 and 94:
Appendix LL.8.21 Table: S_PFD_Ln [O
Page 95 and 96:
Appendix LTable: S_PLSS_Ar [October
Page 97 and 98:
Appendix LST_FIPS R State FIPS. Thi
Page 99 and 100:
Appendix LL.8.24 Table: S_Profil_Ba
Page 101 and 102:
Appendix LFLD_PROB3 A Description o
Page 103 and 104:
Appendix LL.8.26 Table: S_Stn_Start
Page 105 and 106:
Appendix LL.8.27 Table: S_Subbasins
Page 107 and 108:
Appendix LL.8.28 Table: S_Submittal
Page 109 and 110:
Appendix LField R/A TypeTable: S_Su
Page 111 and 112:
Appendix LTable: S_Trnsport_Ln [Oct
Page 113 and 114:
Appendix LField R/A TypeTable: S_Ts
Page 115 and 116:
Appendix LTable: S_Wtr_Ar [October
Page 117 and 118:
Appendix LTable: S_Wtr_Ln [October
Page 119 and 120:
Appendix LXS_LTR A Cross Section Le
Page 121 and 122:
Appendix LL.8.34 Table: S_Zone_AR [
Page 123 and 124:
Appendix LH_DATUM R Horizontal Datu
Page 125 and 126:
Appendix LField R/A TypeTable: Stud
Page 127 and 128:
Appendix LIN_ID_DAT R Initial Ident
Page 129 and 130:
Appendix LL.8.37 Table: L_Comm_Revi
Page 131 and 132:
Appendix LSTRM_PRM A Storm Paramete
Page 133 and 134:
Appendix LTable: L_Cst_Model [Octob
Page 135 and 136:
Appendix LField R/A TypeTable: L_Cs
Page 137 and 138:
Appendix LL.8.41 Table: L_ManningsN
Page 139 and 140:
Appendix LL.8.43 Table: L_MT2_LOMR
Page 141 and 142:
Appendix LL.8.44 Table: L_Mtg_POC [
Page 143 and 144:
Appendix LL.8.45 Table: L_Pan_Revis
Page 145 and 146:
Appendix LL.8.46 Table: L_Pol_FHBM
Page 147 and 148:
Appendix LL.8.48 Table: L_Profil_La
Page 149 and 150:
Appendix LL.8.49 Table: L_Source_Ci
Page 151 and 152:
Appendix LL.8.50 Table: L_Summary_D
Page 153 and 154:
Appendix LL.8.51 Table: L_Summary_E
Page 155 and 156:
Appendix LL.8.52 Table: L_XS_Elev [
Page 157 and 158:
Appendix LWSEL_FLDWY A Base Flood W
Page 159 and 160:
Appendix LField R/A TypeTable: L_XS
Page 161 and 162:
Appendix LV_DATUM R Vertical Datum.
Page 163:
Appendix LL.10. Domain Tables [Octo
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Appendix L - Federal Emergency Management Agency

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