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A GIS Flood Tool for Mapping Extent of Inundation

A GIS Flood Tool for Mapping Extent of Inundation. James Verdin USGS Earth Resources Observation and Science verdin@usgs.gov. Motivation. Floods consistently account for a major portion of the world’s annual loss of life and property to natural disasters

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A GIS Flood Tool for Mapping Extent of Inundation

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  1. A GIS Flood Tool for Mapping Extent of Inundation James Verdin USGS Earth Resources Observation and Science verdin@usgs.gov

  2. Motivation • Floods consistently account for a major portion of the world’s annual loss of life and property to natural disasters • Many developing country communities lack flood mapping to build scenarios for mitigation and response planning • USGS developed the GIS Flood Tool (GFT) with support from the USAID OFDA • UNEP and Global Risk Identification Program • Testing and training support by Riverside Technology inc. (RTi) of Fort Collins, Colorado

  3. GFT Concepts • A tool to produce flood inundation patterns given either: • A specified discharge (m3/s) • A specified stage (m) • Translation of discharge to stage is done using the Manning equation for flow in an open channel • Mapping of stage onto land surface is done using aRelative DEM

  4. GFT Software • ArcGIS-based tools, written in Python and VBA • Uses DEMs to: • Derive stream network • Develop cross-sectional information • Provide base for inundation mapping • Can work with any DEM • For our workshops, we used hydrologically conditioned SRTM data (HydroSHEDS-FM)

  5. Manning Equation Wetted Perimeter Area Where: V = mean velocity in meters/second R = hydraulic radius in meters S = slope of the energy line n = coefficient of roughness (“Manning’s n”) Q = discharge (m3/sec) Q = V * A

  6. Height above MSL 10.2 m 13.7 m Mean Sea Level (MSL) Height above River water surface 3.5 m River water surface 0 m Concept of Relative DEM

  7. Query Relative DEM for all values less than 10 meter Q = 6,000 cms H = 10 meters

  8. Training Workshops • Kenya (Sept 2010) at RCMRD in Nairobi • Riverside Technology Inc. in Ethiopia (Jan 2012) • Review concepts of GIS, DEMs, and flood hydrology • Achieve proficiency in the use of the GFT to: • Map the extent of inundation for a given discharge • Create a library of inundation maps corresponding to regular increments of stage • Apply the GFT to participant flood inundation problems

  9. Thank you

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