Module 4: Coastal Flooding

 Module 4: Coastal Flooding

In this weeks module we were focusing on how to use DEM and LiDAR data to see storm surges within 1-meter. This module was more difficult than other ones because you had to do a lot of geoprocessing before being able to do analysis. I did have to rely on past modules to help me get the information I needed for the module.

We were given two data types which were dem_lidar and dem_usgs. The dem_lidar is a high-resolution elevation model for a portion of Collier County, FL created using Lidar data. The dem_usgs is a regular elevation model from the USGS created using traditional methods (i.e. photogrammetry) before Lidar data were available. The first thing we needed to do was reclassify the values to where it showed 1-meter or less within the values. After that we needed to use the raster to polygon geoprocessing tool so that we could use the spatial tool to get the information of how many buildings were disturbed by the storm surge. Being able to get this information is important because it shows how each of the data sets interpreted their storm surge. After creating the polygons I got the select by attribute table and got the join_count to get the selected buildings within each data set. This was more helpful for me to do so that I could focus on just the buildings I needed for the table. Also, when making the map having them as their own layer it made it easier to change the colors. The last aspect we needed for the map was to figure out the error of omission and error of commission. Errors of omission are those buildings impacted by the storm surge based on the Lidar DEM (the “true” scenario) but not identified as such based on the USGS DEM. Errors of commission are the buildings not impacted by the storm surge based on the Lidar DEM but incorrectly identified as such based on the USGS DEM. The image below is how the different buildings looked based off if they were within both the data sets, in one data set, or not in a data set at all. 

As stated earlier this module was one of the most difficult because you needed to not only change from feet to meters but use a lot of geoprocessing tools in order to do any analysis.