High-Water Marks in the Five Boroughs of New York City from Flash Flooding Caused by the Remnants of Hurricane Ida, September 1, 2021

This data release contains results of a high-water mark survey across the five boroughs of New York City following flash flooding caused by the remnants of Hurricane Ida, September 1, 2021.� The survey was conducted between September 7 and November 23, 2021, and is based on observations of mud, debris, and seed lines left by the flooding.� Real time and static GNSS surveying as well as available lidar data were used to determine high-water mark elevations at 83 locations.� Additional data associated with Hurricane Ida flooding can be found in the USGS Flood Event Viewer, https://stn.wim.usgs.gov/fev/#2021Ida