REUSE OF ARCHIVED UAS DATA FOR GIS ANALYSIS OF ICE JAM FLOODING IN PLYMOUTH, NH

This poster reports on GIS analysis performed on archived UAS data collected in response to the Plymouth, NH ice jam of February 2017. Ice jams are a costly occurrence throughout the northern CONUS as noted by the USACE Ice Jam Database (2020). Media Wing Airshark collected the imagery data under contract with the USGS National UAS Program Office (2017) and rapidly processed it for delivery the day following the flight. Data collected with a DJI Inspire 1 with FC550 sensor for image collection over four miles of the Pemigewasset River resulted in a final 3 cm resolution mosaic image of the ice jam impacted area. We accessed the data set from USGS Earth Explorer and processed it with ArcGIS and Pix4D. First, we examined the aerial mosaic of the ice flow in relation to prior high resolution aerial photos. Next, we compare DEMs derived from the aerial imagery with 1 meter resolution USGS DEMs of the area at six transect locations located along the river. Lastly, we overlay the FEMA National Flood Hazard Layer over the image mosaic to assess spatial extent of the ice jam flooding in relation to expected flood extents. Analysis of the UAS data at transects illustrate the extent of the ice jam and provide useful information on flooding potential within an immediate response time. The results indicate rapid deployment of UAS provides actionable information for local communities on location and extent of flooding threats in response to ice dam breaks.