A collaborative project was undertaken to set conservation priorities and identify risks along two watercourses in Orange County, NY. Digital flood inundation mapping, which depicts estimates of the spatial extent and depth of flooding corresponding to select river flows and water surface elevations, was produced for 14.2 miles of the Neversink River and 4.2 miles of its tributary, the Basher Kill. Analysis of stream gauge records and regression equations were used to determine hydrology and estimate flow return intervals. Using HEC-RAS modeling software, one-dimensional hydraulic modeling was employed to determine water surface elevations and calculate specific stream power along both watercourses for a range of flow conditions ranging from the estimated 2-year to 500-year recurrence interval, and including flows recorded during the April, 2005 flood of record. Inundation mapping for the more frequent flow events (the 2-year, 5-year, and 10-year recurrence interval floods) was used to identify opportunities for ecological restoration, prioritize areas for protection, evaluate floodplain connectivity, and identify remnant stream channels, or binnekills. Maps representing the larger and less frequent flow events (the 2005 flood, and the 100-year and 500-year recurrence interval floods) were used to assess risk to inhabited areas resulting from flooding, and combined with stream power calculations to create a coarse-screen measure of potential erosion and channel migration. The resulting products from this study will be combined with other available data such as land cover, soil mapping and field observations, to further refine conservation prioritization and risk assessment. River reaches were identified where an understanding of complex flow conditions is required, and the application of more powerful, two-dimensional hydraulic modeling may be warranted.

Mark Carabetta, PWS, CFM is a senior environmental scientist responsible for an array of ecological inventory, river and wetland restoration, and flood mitigation projects. He has led numerous conservation, restoration and flood mitigation projects in New York, New England, and southern Ontario. Mr. Carabetta has degrees in botany and natural resources management and engineering, and is a certified wetland scientist and floodplain manager with over 20 years of experience in the environmental field. Mr. Carabetta manages Milone & MacBroom's regional office in New Paltz, New York.