Flood-Inundation Maps for the Schoharie Creek at Prattsville, New York

Prattsville has experienced severe flooding along the Schoharie Creek, most notably during August 2011 following Hurricane Irene, which severely damaged or destroyed large areas of the town, and caused several million dollars in damages (Figure 1).

Before and during a flood, forewarning and emergency response are critical. The rescue efforts of emergency responders are often hampered by lack of an understanding of where flooding is occurring at any given moment, but also where flooding is likely to occur in the near future. Emergency responders would benefit from a library of flood-inundation maps that are referenced to the stages recorded at the U.S. Geological Survey (USGS) streamgage in Prattsville. By referring to the appropriate map, emergency responders can discern the severity of existing and predicted flooding (depth of water and aerial extent), identify roads that are or will soon be flooded, and make plans for notification or evacuation of residents in harm’s way.

Objective and Approach

Digital flood-inundation maps for a 2.6 mile reach of the Schoharie Creek at Prattsville, New York (Figure 2) will be created by the USGS in cooperation with the New York State Department of Environmental Conservation. Flood profiles will be computed for the stream reach by means of a one-dimensional step-backwater model; this model will be based on existing models where available, but will be updated to reflect current ground conditions following the August 2011 flood. This hydraulic model will be used to compute 17 water-surface profiles for flood stages at 1-foot intervals referenced to the USGS streamgage Schoharie Creek at Prattsville, N.Y. (station number 01350000) for stages 9 to 25 feet, which exceeds the estimated 0.2-percent annual-exceedance-probability flood, or 500-year recurrence interval flood.

The simulated water-surface profiles will be combined with a geographic information system (GIS) digital elevation model derived from Light Detection and Ranging (LiDAR) data to delineate the area flooded at each water level and to map the estimated depth of water. These flood maps will be overlaid on high-resolution, georeferenced, aerial imagery of the study area in the form of static maps, and will also be available on the USGS Flood Inundation Mapper website: (https://fim.wim.usgs.gov/fim/?site_no=01350000) which displays current USGS and predicted (from the National Weather Service Advanced Hydrologic Prediction Service) stages, has a variety of basemaps, and allows users to interact with model results and inundation scenarios.

Related Publications

Coon, W.F., and Breaker, B.K., 2012, Flood-inundation maps for the West Branch Delaware River, Delhi, New York, 2012: U.S. Geological Survey Scientific Investigations Map 3216, 9 p. pamphlet, 10 sheets, scale 1:20,000. Available online at http://pubs.usgs.gov/sim/3216

Project Location by County

Delaware County, NY, Greene County, NY