This post is a short recipe for a longer lesson that you can complete on the Learn ArcGIS website. You’re in the right place if you:
- Want to find areas at risk from storm surge flooding
- Have some pre-existing GIS skills
- Don’t have a lot of time
Full lesson: Map Hurricane Storm Surges. If you are unclear about anything in this recipe, consult the lesson.
Ingredients:
1. ArcGIS Pro, with either the Spatial Analyst or Image Analyst extensions
2. Elevation raster data.
- You can use the Terrain Imagery Layer from Living Atlas, which has coverage of the entire world.
- You can use your own data. You need a raster layer where each cell has an elevation value. A Digital Elevation Model (DEM) is ideal.
Process:
1. Zoom to your area of interest.
2. Export a new raster layer from the Terrain layer that only covers your area of interest.
- In the Contents pane, right click Terrain, point to Data, and choose Export Raster.
- For Clipping Geometry, choose Current Display Extent.
- Decrease the Cell Size if the file size is too large to export.
![Export Raster pane Export Raster pane](https://www.esri.com/arcgis-blog/wp-content/uploads/2020/08/export-raster.png)
3. Remove the original Terrain layer from the map.
4. Use the Con tool with your new Terrain.tif layer to assign a value of 1 to low lying areas and a value of 0 to high ground.
- Add an expression like this: Where VALUE is less than or equal to 3. 3 is an arbitrary value representing the storm surge. If you want to map a 5 meter storm surge, change this value to 5.
- For Input true raster or constant value, type 1. For Output, type 0.
![The Con tool in the Geoprocessing pane The Con tool in the Geoprocessing pane](https://www.esri.com/arcgis-blog/wp-content/uploads/2020/08/con-tool.png)
5. Symbolize the new raster so values of 0 have no color and values of 1 have a transparent color.
6. Compare the new layer to a basemap to explore which areas are at risk from storm surges.
![Map with storm surge in blue Map with storm surge in blue](https://www.esri.com/arcgis-blog/wp-content/uploads/2020/08/flood.png)
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