According to NOAA’s National Weather Service, a flash flood is a life-threatening flood that begins within 6 hours--and often within 3 hours--of a causative event. That causative event can be intense rainfall, the failure of a dam, levee, or other structure that is impounding water, or the sudden rise of water level associated with river ice jams.
The “Flash Flood Processes” module offers an introduction to the distinguishing features of flash floods, the underlying hydrologic influences and the use of flash flood guidance (FFG) products. Through use of rich illustrations, animations, and interactions, this module explains the differences between flash floods and general floods and examines the hydrologic processes that impact flash flooding risk. In addition, it provides an introduction to the use of flash flood guidance (FFG) products including derivation from ThreshR and rainfall-runoff curves as well as current strengths and limitations.
July 2020 - The lesson was updated to current internet standards (mp4/html5), with no changes to content.
July 2014: Section 3 of this module focuses on the legacy Flash Flood Guidance (FFG) methodology used in the NOAA/NWS River Forecast Centers. Since the time of publication (2006) other methodologies for FFG generation have replaced the legacy product. These other methodologies (Gridded Flash Flood Guidance-GFFG, Flash Flood Potential Index-FFPI, Distributed model-based FFG) are not covered in the FFG section.
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