Creating an ArcGIS Hydro Data Model Extension for Flood Plain Mapping
The ArcGIS Hydro Data Model can be easily adapted to display
purely cartographic data, such as the types of data used in creating flood plain
maps for the Federal Emergency Management Agency (FEMA) and the National Flood
Insurance Program (NFIP).
This chapter describes the following:
· FEMA's Digital Flood Insurance Rate Map (DFIRM) database
· DFIRM data requirements
· Creating DFIRM Features
· Modifying the ArcGIS Hydro Data Model to support a DFIRM database
· Creating a flood plain map
Click here to view the PDF version of Chapter 11.
Chapter 11 Data
The Benchmarks feature class contains a benchmark elevation point depicted on the existing FIRM. The Bridges, Buildings, and Docks classes contain polygons outlining their respective features. The Corporate Limits and Etj classes are line features delineating city limits and extraterritorial jurisdictional areas. The Parcels feature class includes polygons and attribute information of each parcel along the river.
The Neatlines class shows the grid used for FEMA's Digital Flood Insurance Rate Map (DFIRM) panel index. The Hydro Junction, and Watershed feature classes do not contain any data and are created when applying data to the ArcGIS Hydro Data Model DFIRM Extension. The Roads class contains the attribute data used to label the roads near flood hazards. The classes Waterbodies and Hydro Edge show the location of all streams, river, lakes and creeks.
The Contours and Spot Elevations provide the elevation information used to develop the floodplains. The contours are available to the reader at the CRWR ftp site at ftp://ftp.crwr.utexas.edu/pub/consortium/DFIRM. The Floodplain class displays the flood hazards shown on DFIRMs, including the 100 and 500-year floodplains. This layer has been omitted from the geodatabase on the CD-ROM pending approval of the flood map panel by FEMA. The Waterbodies Annotation and Roads Annotation classes are created in ArcMap when labeling features.
The geodatabase does not contain the base map image used for the DFIRM panel, because a geodatabase is unable to hold raster data. The image file, Basemap.tif, can be found in the folder ArcGIS\Chapter11\Chapter11Data.
This geodatabase includes more than the required data for a standard DFIRM database. However, a DFIRM database may contain much more information than is shown here. The Parcels, Buildings, and Spot Elevations classes are all examples of data that is neither required in the DFIRM database nor shown on the flood plain map, but can provide useful information.
The geodatabase (in zipped format) can be found in the folder ArcGIS\Chapter11\Chapter11data, along with the DLL file needed in order to run the ArcGIS Hydro Data Model in ArcCatalog or ArcMap. For instructions on how to use the DLL file and deploy the data model, go to the Instructions page.
Chapter 11 Display
The data from Chapter 11 can be viewed as a map document or template in ArcMap.
This DFIRM map example can be found in the folder ArcGIS\Chapter11\Chapter11Data and viewed in ArcMap.
