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Developing Digital Flood Insurance Rate Maps for Lago VistaBy Kevin Michael Donnelly and David R. Maidment ABSTRACT Flood Insurance Rate Maps (FIRMs), managed by the Federal Management
Agency, display flood hazards and are used to calculate insurance
premiums for the National Flood Insurance Program. This research
presents an approach for developing new data included in a DFIRM
database, as well as converting existing map data into digital format.
A raster base map combining USGS Digital Orthophoto Quadrangles
(DOQs) and community developed digital orthophotos was created.
Flood hazard zones were redelineated based upon previously determined
100-year and 500-year water surface elevations and recently developed,
detailed contour data. This study also demonstrates how a DFIRM
data model can be developed to run off an existing geodatabase model.
The ArcGIS Hydro data model was extended to contain DFIRM features
based upon FEMA's Standard DFIRM Spatial Database. An evaluation
of the 100-year floodplain developed using "approximate"
study methods (FEMA's Zone A) and a procedure for converting contour
data between the vertical datums, NGVD29 and NAVD88, are also presented.
The methodology is applied to a study area surrounding Lago Vista,
Texas. The results of this research indicate that GIS is an effective
environment for developing, utilizing, and storing Flood Insurance
Rate Maps. The highlighted links that follow are connected to Adobe pdf files of the corresponding material. To view them you must have the Adobe Acrobat Reader 3.0. View the Report...(2.7MB)
These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 1997 Center for Research in Water Resources. |
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