Module 3 - Coastal Flooding

 

Figure 1 - NJ Coastal Flooding

Figure 2 -  Fl Coastal Flooding

In Part 1 of the lab, I explored how GIS and LiDAR can be used to analyze natural disasters, focusing on Hurricane Sandy’s impact on Mantoloking, New Jersey. My goal was to measure erosion caused by the storm using pre‑ and post‑event LiDAR data. After loading both datasets into a 3D scene, I compared the pre‑ and post‑storm point clouds to observe visible differences.

Next, I created DEMs by converting each LAS file to a TIN and then to a raster. Using Raster Calculator, I subtracted the pre‑storm DEM from the post‑storm DEM to highlight areas of erosion and deposition. The red‑to‑blue color ramp helped me visualize where the storm removed sand, destroyed structures, or deposited debris. I then compared these changes with building footprints and imagery using bookmarks to answer questions about rebuilding, damage patterns, and data reliability

 In part 2 of the lab, I modeled a 1‑meter storm surge using both the LiDAR DEM and the USGS DEM to see how each dataset affects flood mapping results. I created flood rasters by selecting all areas below the surge height, used Region Group to identify connected flood zones, and kept only the region that was truly connected to open water. I then converted the flood areas to polygons and performed spatial joins to determine which buildings were flooded according to each DEM. All in an effort to determine the accuracy of the DEM’s.

Throughout the process, I had to troubleshoot several issues, including incorrect data paths, confusion about Region Group values, verifying that “0” meant not flooded, and fixing queries for omission and commission errors. I also resolved problems with map layout, such as removing unwanted basemap labels. After calculating errors, I found that the USGS DEM produced extremely high commission rates, meaning it greatly overestimated flooding. Because of this, I used the LiDAR results for my final map since they were more accurate and realistic.