Floodplain Management

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Flooding in the Carson River Watershed is a natural process that occurs on a regular basis. It is also one of the most devastating and costly natural events that our communities face. Serious flooding can happen approximately every 10-20 years and often occurs after rain-on-snow events or summer thunderstorms. The Carson River is unique; there is extremely limited upstream water storage capacity or capability, and there are no flood control structures within the river.  However, open floodplains, especially in Hope Valley, Carson Valley, and Dayton Valley, provide our watershed with the best flood control mechanisms available!

During a flood, open floodplain benefits our watershed by storing and slowing flood waters; helping protect our natural resources such as drinking water and wildlife habitat; and avoiding costly damages to structures associated with more developed lands. Protecting the natural functions and values of our floodplain areas are central to maintaining a “living river” and limiting the devastating property loss from flooding in our watershed. Carson Water Subconservancy District (CWSD) works closely with our partners in the Carson River Coalition (CRC) to coordinate, plan and fund numerous studies, plans, and on-the-ground efforts to create watershed-wide solutions that reduce our flood risk and protect our floodplain.

In 2003, the University of Cooperative Extension surveyed CRC members to identify the most important issues that are facing our watershed.  The top concern, reconfirmed by the CRC in 2012, is as follows:

“Protect the floodplain from future development. Once the floodplain and especially the river’s meander belt corridor are impacted by development, the river loses the ability to reestablish its natural functions.  Agricultural fields near the channel are critical for floodwater attenuation, ground water recharge, non-point source pollution buffering and providing habitat for wildlife.”

Some examples of our efforts are listed below:

CWSD coordinates stakeholders throughout the watershed through:

• CRC Forums and Meetings
• Housing and partially funding the CRC/Watershed Coordinator position since 1999
• The River Corridor Working Group, a sub-group of the CRC that meets regularly about issues     affecting the river corridor.
• In 2005, CWSD signed the Cooperative Technical Partner Agreement with Federal Emergency Management Agency (FEMA).
• In 2012, the various counties located along the Carson River, State and Federal agencies entered into a Risk MAP Charter agreement with FEMA.  The Charter agreement enables FEMA and CWSD to work on flood related issues on a watershed basis instead on a county by county basis.  This is the first Charter Agreement in FEMA Region 9 and is a blueprint for other regional cooperation programs.

CWSD produces planning documents:

• Carson River Watershed Regional Floodplain Management Plan, 2008
• Carson River Watershed Regional Floodplain Management Plan Supplemental Update, 2013
• Carson River Watershed Adaptive Stewardship Plan 2007
• Hydraulic Modeling and Floodplain Mapping Guidelines, Carson River, NV & CA, October 2011
• FEMA RiskMap Discovery Report, December 2012
• Revising FEMA Flood Hazard Maps from Lahontan Reservoir to beyond Alpine County, CA (in progress through grants from FEMA).

CWSD provides funds to support:

• CRC/Watershed Coordinator since 1999
• On-the-ground flood protection and river enhancement projects
• Research and studies to assess flood issues, risk and solutions
• Preparation of planning documents (examples above)
• Flood awareness program