This module takes the learner through seven case studies of flash flood events that occurred in the conterminous U.S. between 2003 and 2006. The cases covered include:
- 30-31 August 2003: Chase & Lyon Counties, KS
- 16-17 September 2004: Macon County, NC
- 31 July 2006: Santa Catalina Mountains near Tucson, AZ
- 25 December 2003: Fire burn area near San Bernardino, CA
- 30 August 2004: Urban flash flood in Richmond, VA
- 19-20 August 2003: Urban flash flood in Las Vegas, NV
- 9 October 2005: Cheshire County, NH
This module assists the learner in applying the concepts covered in the foundation topics of the Basic Hydrologic Sciences course. Some of the specific topics pertinent to these cases are the physical characteristics that make a basin prone to flash floods, basin response to precipitation, flash flood guidance (FFG), the relationship between wildfire and flash floods, and the relationship between urban development and flash floods. Related topics brought out in the cases include radar quantitative precipitation estimation (QPE), the National Weather Service Flash Flood Monitoring and Prediction (NWS FFMP) products, debris flows, impounded water, and interagency communications. The core foundation topics are recommended prerequisite materials since this module assumes some pre-existing knowledge of hydrologic principles. In particular, the Runoff Processes and Flash Flood Processes modules contain material directly related to these cases.
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- Understand the hydrologic response to intense rainfall that leads to rapid runoff and flash floods.
- Recognize the utility and limitations in NWS flash flood forecasting tools (FFMP, FFG, Radar QPE).
- Understand that flash flood prone basins can be very small.
- Identify the LEC (Low Echo Centroid) storm signature and realize its implications on rainfall production.
- Understand the utility and limitations of different Z-R relationships.
- Recognize the information provided by FFMP's (Flash Flood Monitoring and Prediction) upstream/downstream tool.
- Recall how and why FFMP basin rainfall can mask radar problems such as terrain blocking.
- Think about how one may use other data in areas with terrain blocking of the radar beam.
- Understand the impact that fire may have on basin hydrology.
- Recall how debris flows can occur with flash floods.
- Understand how changing the FFG values may be appropriate in some situations.
- Recognize the important information provided by FFMP's difference and ratio fields.
- Be aware of important collaborative efforts between the NWS and other agencies, such as the USGS.
- Understand the dramatic impact that urban and suburban development can have on basin response.
- Understand how and why FFG may need to be altered in urbanized areas.
- Anticipate the very short time lag between peak rainfall and peak flooding in urbanized areas.
- Recognize that flash flooding may occur downstream of basins that receive the greatest rainfall.
- Recognize the potential of flash flooding from the sudden release of water impounded by human engineered structures.
- Recognize the importance of interagency communication prior to and during flash flood events, especially those that involve structural failures.
hydrology, hydrologic cycle, runoff, flash flood, flash flood prediction, flood frequency, Flash Flood Guidance (FFG), Quantitative Precipitation Estimation (QPE), Flash Flood Monitoring and Prediction (FFMP), Low Echo Centroid (LEC), catchment, drainage, frontogenesis, theta-e, radar reflectivity, satellite, Z-R coefficients, warm-rain process, basin, sounding, downstream, upstream, precipitation efficiency, rainbands, debris flow, slope failure, beam blocking, multi-sensor rainfall, FFMP difference field, FFMP ratio field, FFMP basins, orographic lift, burn area, burn severity, radar coverage, rainfall threshold, time since burn, urbanization, cubic feet per second (cfs), cubic meter per second (cms), basin response, infiltration, culverts, storm sewer, road grid, dry wash, impounded water, structural failure, radar overshooting
July 2020 - The lesson was updated to current internet standards (mp4/html5), with no changes to content.
