A Simple Method to Create Flood Inudation Models

In my class this week, my students asked me to show them how I created some of the flood inudation models.  The lab is a bit tricky to customize with tools like Arc Hydro or Hazus, but I was thinking, when I had an emergency situation and needed a flood zone I turned to QGIS and GRASS to create a quick inudation model. It worked well enough for discussion during the drill and thought that it would be a good way for the students to work with it.

GRASS needs be setup in a location before working with it.  In the past this was a barrier for some to use it, but in the new version, you can use an existing layer as a refrence point.  For my example I was using an elevation model of Oatka Creek so I loaded that.  Screen Shot 2016-04-11 at 7.40.55 PMScreen Shot 2016-04-11 at 7.41.03 PMScreen Shot 2016-04-11 at 7.41.40 PMScreen Shot 2016-04-11 at 7.42.13 PM

Then you can load the Mapset and Add your elevation data.  I changed my symbology to the Elevation ramp.  Screen Shot 2016-04-11 at 7.44.08 PM

The tool for this example is the Fill lake (r.lake) and what that does is basically fills water at a known point (like a gage station) to a level that you specifiy.  The tool is located in the Raster ser under Hydrologic Modeling.

Screen Shot 2016-04-11 at 7.44.20 PM

The tool is pretty easy to run.  You need your elevation and a water level.  In the optional tab, I add the export raster and the seed point.

Screen Shot 2016-04-11 at 7.44.54 PMScreen Shot 2016-04-11 at 7.44.59 PM

This only took a few seconds to run and created an inudation map for that location.  It is not perfect, but depending on what you need it may be good enough.

Screen Shot 2016-04-11 at 7.45.14 PM

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