Flooding occurs when climate (or weather patterns), geology, and hydrology combine to create conditions where river and stream waters flow outside of their usual course and “overspill” beyond their banks.
In Clark County, the combination of these factors, in addition to ongoing development, create chronic seasonal flooding conditions.
Flooding is most common from October through April, when storms from the Pacific Ocean, 60 miles away, bring intense rainfall to the area. Clark County receives approximately 40 inches of rain on average each year.
Larger floods result from heavy rains that continue over the course of several days, increased by snowmelt at a time when the soil is near saturation from previous rains. Frozen topsoil also contributes to the frequency of floods.
Floods in recent years were caused by these types of circumstances.
Riverine flooding and urban flooding are the two types of flooding that primarily affect Clark County.
Riverine flooding is the overbank flooding of rivers and streams, the natural processes of which add sediment and nutrients to fertile floodplain areas. This list (PDF - 40K) contains the many rivers and streams in Calrk County that flood.
Urban flooding results from the conversion of land from fields or woodlands to parking lots and roads, through which the land loses its ability to absorb rainfall.
Is your property in danger of flooding? Maps are available online. Use these instructions to find that information. Elevation certificates may be available for properties in the Special Flood Hazard Area at our offices. You can speak with a trained permit technician or pick up additional information at our downtown Permit Center located at 1300 Franklin St., Vancouver or at our Battle Ground location at 1808 SW 9th Ave. Bldg C, Suite 101. Battle Ground. You can call us at (360) 397-2375.
