A GIS STUDY OF THE FLOODING FROM HURRICANE IDA ON STATEN ISLAND, NY

During September 1-2, 2021 Staten Island experienced very heavy rainfalls from Hurricane Ida that resulted in extensive flash flooding. The National Weather Service reported rainfall amounts ranging from 5.81 inches to 9.64 inches for Staten Island (Richmond County, NY). The NYS Mesonet weather station at the College of Staten Island recorded 8.31 inches of rain.

In order to study the effects of flooding on Staten Island this author has plotted the following on a LiDAR DEM in a GIS: Pre-1900 Staten Island streams; present day streams; Staten Island Bluebelts; NYC contour lines with a 2 foot contour interval; data from NYC recently published stormwater maps; and Staten Island streets and buildings with blocks and lots. Since many of the Staten Island streets slope, the intersection of the streets with the contour lines provided flow directions for the storm water. Much of the flooding can be explained by this GIS study.

In addition, during this rainfall event, this author monitored the FDNY scanner frequency and recorded many locations where rescuing of motorists occurred on flooded roadways. In many instances the FDNY indicated water depths. These locations were then plotted on the GIS.

Furthermore, since we now know the locations of potentially flooded roadways, Staten Island residents could be alerted to the depth of future flooding by the installation of “road may flood” signage with at least a 5 foot staff gauge.