Floodplains

Floodplains store water for later release. Floodplains and wetlands help recharge aquifers. An aquifer is the underground water storage vessel that receives water percolating down after infiltration and retains it for a period of time before gravity drains it out through a spring or seep or it is withdrawn from a well. Wetlands also function as both belowground sponges and above-ground reservoirs. A floodplain next to a stream acts as a lake while the stream is in flood, releasing the water slowly rather than all at once as it would if the stream was in a big concrete ditch.

Understanding risks of living near a floodplain
As people continue to build in floodplains, they change the height of flood flows. Buildings take up space that would previously have accommodated flood flows. Impervious surfaces cause more rapid runoff and less infiltration.

Levees or other structures that attempt to contain flows in the channel cause problems and will eventually fail. Levees or berms placed a distance from the edge of the stream allow room for floodwaters to spread out and soak in. When placed far from the stream, levees or berms need not be high. Often they are so low that they are hardly noticeable.

Make sure that any flood protection does not adversely affect neighbors.

Insurance
Sooner or later, a floodplain will flood. If you must build on it, put the building on stilts or make the bottom level into flood compatible spaces such as carports, garages, unfinished storage areas, etc. Recognize that a 100-year flood has a 1 percent chance of flooding at that level or greater every year, even if it flooded that high last year. You assume a risk when you choose to live in a floodplain. Insurance can help in an emergency, but the flood will still disrupt your life.

Local ordinances may limit development to flood-compatible land uses within floodplains. Make sure all land uses in a floodplain are compatible with local stream ordinances. A local stream ordinance may require:

• set back limits for any buildings,
• set back limits for other construction activities, such as patios or decks, excavation, or storing or using heavy equipment,
• maintaining vegetation or buffers,
• permits before any stream alterations, including restoration, bridges or roads,
• no dumping into streams, etc.

Put Flood-compatible Uses in Floodplains
Flood-compatible uses allow hydrological and many biological processes to continue. Areas such as parks and recreational areas are far less likely to suffer permanent or expensive damage in floods than expensive buildings, businesses, or developments. Use of these areas is more easily avoided during a flood.

• Parks
• Recreation
• Open Spaces
• Agriculture
• Wildlife Habitat
• Parking Lots

Modified from Living on the Land 2001: Stewardship for Small Acreages
Project Leaders: Susan Donaldson, University of Nevada, Cooperative Extension
and Sherman Swanson, University of Nevada, Reno

Return to regular view	Text-only	Updated: 08/28/2009