The USGS has been funded by the Federal Emergency Management Agency through Nevada’s Floodplain Management Program, Nevada Division of Water Resources, to make publicly available historic flood information for the Carson River Basin. The focus of the project is on existing data, both factual and anecdotal, the latter for flood events prior to streamflow monitoring. The data is being made public through the USGS “Flood Chronology of the Carson River Basin, California and Nevada” web site.
The development of the web site included the following steps:
1. Define criteria for selecting flood events. Decisions regarding which flood events to include in this web site were two-fold. First, notable events as published in the literature received primary consideration. Second, using the flood-frequency analyses, streamflows of lesser magnitude than the primary events, though occurring at a higher frequency (see the page “ What is a flood frequency” for further discussion) were selected to illustrate flooding risk posed to those areas in close proximity to the Carson River floodplain and its channel. In addition, flood events affecting active alluvial-fan surfaces where included given the rapid development in these areas.
2. Develop a database for storage and retrieval of flood-related information.
3. Generate tables and graphs summarizing flood statistics and general hydrologic information. Flood-frequency plots were generated using the program, PEAKFQ (Thomas and others, 1998; USGS, 1982). Hydrologic data from the USGS surface-water database are available for the flood events included in this web site.
4. Provide descriptive accounts of the selected flood events.
5. Create an annotated historical flood photo archive. Photographs have been collected from local historical societies, federal and state agencies, newspapers, and private collections.
6. Include short excerpts from videos depicting flood events. Video footage is available for the 1955, 1986, 1991, 1994, and 1997 floods illustrating the regional extent of Carson River flooding and alluvial fan flooding in Carson Valley.
Thomas, W.O., Jr., Lumb, A.M., Flynn, K.M., and Kirby, W.H., 1998, User's manual for program PEAKFQ, annual flood frequency analysis using Bulletin 17B guidelines, written communication, 89 p.
U.S. Geological Survey, 1982, Guidelines for determining flood flow frequency: Interagency Advisory Committee on Water Data, Bulletin 17B of the Hydrology Committee, available online at <http://water.usgs.gov/osw/bulletin17b/dl_flow.pdf>
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