Chapter 10 - Flood Forecasting in the United States NOAA/National Weather Service

Abstract

In the United States, the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) has official responsibility for issuing public routine river and flood forecasts, for the purpose of protection of life and property. The focus of this chapter is a discussion of the models and methodologies developed by the NOAA/NWS for flood forecasting. Since the formation of the 13 River Forecast Centers (RFCs), covering all U.S. states and territories, scientific and technological developments have been significant. Methodologies have evolved from the use of manually intensive graphical and hand-calculated modeling and forecast procedures, to locally developed event-based hydrologic modeling systems in the 1970s and 1980s. This was followed by the emergence of the mainframe computer system-based NWS River Forecast System (NWSRFS) in the late 1970s and early 1980s, developed by the NWS Office of Hydrology. The creation of NWSRFS and subsequent availability of UNIX-based computer workstations made the development of interactive hydrologic forecasting feasible in the early 1990s for use at RFCs for routine operations. This was a time of NWS modernization with the Advanced Weather Interactive Processing System (AWIPS), Next Generation Radar (NEXRAD), and, within NWS hydrologic services, implementation of the Advanced Hydrologic Prediction Services (AHPS). The modernization brought a significant infusion of hydrologic science and technology, including long lead-time probabilistic hydrologic forecasting, mainly for water resources applications, a world-wide-web presence, and the widespread use of gridded flash flood guidance. The NWS is currently in the process of implementing AWIPS-2 and RFCs recently completed the transition from NWSRFS to the Deltares-based (the Netherlands) Flood Early Warning System (FEWS) flood forecast system, called the Community Hydrologic Prediction System (CHPS) by the NWS. Significant emphasis is now being placed on implementation of distributed hydrologic modeling and hydrologic ensemble forecasting, especially for near-term and intermediate lead-time flood forecasting, as well as long lead-time forecast for water resources needs. NOAA/NWS RFCs are emphasizing development of improved streamflow routing with the use of dynamic, unsteady streamflow routing, including near real-time event-based flood inundation mapping, within CHPS. A detailed discussion of the models, forecast procedures, and systems used by NOAA/NWS/RFCs is presented.