Drought in Nevada: The Power of the Watershed Approach for floodplain management

The Power of the Watershed Approach for floodplain management

by John Cobourn, Extension Water Specialist, University of Nevada Cooperative Extension

One truism often repeated is that droughts end with major floods. Although every major flood may not be the end of a drought, some of Nevada's river systems have had significant flooding, leading to extensive and long lasting damage (http://pubs.usgs.gov/fs/1997/0182/report.pdf).

I have said that community water issues can be best understood in the context of the whole watershed. I also stated that on the Carson River in Nevada, the Carson Water Subconservancy District (CWSD) sponsors a community watershed group called the Carson River Coalition (CRC). It views all issues in the watershed in terms of integrated watershed management (IWM). This approach says problems with water quality, water supply, fish and wildlife habitat and floodplain management should be addressed in an integrated fashion.

Through a consensus process, the CRC has designated its most important single issue, the Main Message of the Coalition, to be protecting natural floodplains from urban development. (www.unce.unr.edu/publications/files/nr/2004/fs0471.pdf) This is a good example of the power of the watershed approach. Urban development on low-lying river floodplains puts the infrastructure built there at risk of damage from the very large floods that occur every fifteen years or so. It also converts valuable agricultural land to pavement and rooftops, and it destroys wildlife habitat.

After large floods cause damage to homes or businesses, communities generally build levees along the river channel to protect infrastructure. After a few cycles of larger floods, higher levees and more development, the river could be put in an extremely expensive concrete-lined ditch, like the Los Angeles River. The wildlife habitat will be lost, and recharge of groundwater aquifers will be reduced. The water quality will often be that of urban stormwater runoff, which tends to be poor.

Since everything in a watershed is interconnected, the CRC does not want to solve a flooding problem in ways that would create water quality or wildlife habitat problems. To preserve the natural functions and values of the river and its floodplain, they recommend using floodplains for agriculture, parks and other open space uses. Keep residences and businesses out of the floodplain, and there will be fewer flooding problems. The CRC’s recommendations for floodplain management can be viewed in the Carson River Watershed Regional Floodplain Management Plan (http://www.cwsd.org/wp-content/uploads/2014/07/FinalDraftfloodplainplan7-08.pdf)