APPLICATION OF THE US FEDERAL EMERGENCY MANAGEMENT AGENCY (FEMA) PUBLICATION 94, FOR INFLOW DESIGN FLOOD (IDF) EVALUATIONS ON HIGH-HAZARD NRCS DAMS IN MASSACHUSETTS

摘要

The US Department of Agriculture (USD A), Natural Resources Conservation Service (NRCS), Massachusetts State Office, is currently evaluating several dams in the Sudbury/Assabet/Concord (SuAsCo) Watershed for compliance with current Massachusetts Department of Conservation and Recreation, Office of Dam Safety (DCR/ODS), and NRCS criteria for High Hazard Dams under existing and full build-out watershed conditions. On some of the dams, the NRCS is evaluating the possibility of using an Inflow Design Flood (IDF) for the Freeboard Hydrograph (FBH) lower than that required by Technical Release (TR) 60 (i.e. the Probable Maximum Precipitation (PMP) for a High Hazard Dam), prior to developing rehabilitation plans. Justification for lowering the IDF is established through an engineering analysis of the IDF based on the Federal Emergency Management Agency (FEMA), Publication 94, entitled "Federal Guidelines for Dam Safety -Selecting and Accommodating Inflow Design Floods" (FEMA 94; Reference 1); as interpreted by Hoeft and Locke (Reference 2) for application to NRCS dams. This paper presents the methodology, approach, and findings for IDF evaluations on five (5) High-Hazard Dams within the SuAsCo Watershed in Massachusetts; Hop Brook, Rawson Hill, Cold Harbor, Delaney, and Tyler. The evaluations included considerations for dams in series and how this affected the approach and results.