Eric Tate  
GIS Project Proposal:
Display of Flood Water Levels in a GIS

etate@mail.utexas.edu 


Background
Since the mid 1960's, hydraulic river modeling has been conducted using the computer model HEC-2, designed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers. In the early 1990s, HEC released the Windows version of HEC-2, called HEC-RAS. Using HEC-RAS, the user can calculate water surface profiles at user-input stream stations for steady flow in channels. This type of information would be quite valuable viewed in a GIS environment such as ArcView, in which a coverage of a RAS-calculated floodplain could be compared to coverages of existing structures such as homes, businesses, and transportation arteries. As such, developing a methodology to display flood results in ArcView would be useful.

The steps involved in the process will likely include the following:

  1. Run HEC-RAS to generate water surface elevations for a given flow rate.
  2. Read the stream geometry and water surface profiles from the RAS report text file.
  3. Write the stream information to an ArcView table.
  4. Create a line coverage of the stream centerline.
  5. Link a known point in the centerline to a corresponding point in a river digital line graph or river reach file.
  6. Add remaining cross-section coordinates to the coverage, perpendicular to the stream centerline.
  7. Develop a interpolation algorithm to determine the floodplain boundaries between known stream cross-sections.
  8. Compare existing coverages to the floodplain coverage to determine if structures will be impacted.

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