GIS for Faster Analysis of Dam-Break Flows Steve Pitman GIS in Water Resources – Fall 2003 Dr. David Maidment – UT Austin

The Problem: A breached dam releases large volumes of water very rapidly Can’t predict dam-break floods using observations of natural floods Existing dam-break models –Complex, tricky and time consuming –Not conducive to rapid analysis

Dams in the U.S. Approx. 77,000 total Consider a worst case scenario: On the Colorado River, Glen Canyon Dam and Hoover Dam, 370 miles apart, created Lake Powell and Lake Mead with combined storage equal to roughly four times the river’s annual flow. USBR Photo Lake Powell What would this water do if rapidly released?

Teton Dam, Idaho – June 5, 1976 Teton Dam, Idaho – present day

GIS in Dam-Break Analysis Today Pacific Disaster Center uses the M2M interface to translates FLDWAV output for display in ArcGIS NWS developing FLDWAV-GIS link for displaying flood predictions PBS&J (FEMA Contractor) has fielded a Watershed Analyst extension that automates pre- and post-processing of watershed modeling data

Current Dam-Break Models DWOPER & DAMBRK developed by National Weather Service (NWS) in 1970’s NWS released FLDWAV in 1990’s –Combined DWOPER & DAMBRK –Added functionality Input: Dam parameters Valley geometry Output: Flow rates & depths at selected locations Estimate breach characteristics Geometry Formation time Outflow Hydrograph Flood Routing Finite-difference solution of dynamic wave equations

Adding Automation with GIS Geodatabase GIS Geospatial data Time Series data Interface Data Model Pre-ProcessingPost-Processing

Example USGS – The National Map

Resources Applied Hydrology, Chow et al, McGraw Hill (1988) U.S. Geological Survey websites U.S. Bureau of Reclamation websites National Inventory of Dams, U.S. Army Corps of Engineers Arc Hydro, Maidment, ESRI Press (2002) Source of photos