Flood Plain Management | Surface Water Management | Public Works and Utilities

Public Works & Utilities >> Surface Water Management >> Flood Event Information >> Flood Plain Management

One of the many attractive features of Pierce County is the system of glacial rivers running from Mt. Rainier to Puget Sound. Located in fertile agricultural valleys, supporting salmon runs and recreation, these scenic rivers can quickly turn dangerous, sweeping away everything in their path. Responsible usage of the rivers and the surrounding floodplain to minimize flood losses and maximize other beneficial uses is the goal of the floodplain management approach.

Regulations

Many agencies, including local, County, and State departments, Federal agencies and Tribal organizations, control usage of flood-prone areas.

The Federal Emergency Management Agency (FEMA) has taken the lead with the National Flood Insurance Program to require that all new structures built within the floodplain be elevated above the 100-year flood level, and limits filling in the floodplain. Flood insurance through FEMA is available to homeowners and is required when flood-prone properties are sold or refinanced.

Any work in or near a wetland, including riverine wetlands, is regulated by the Corps of Engineers (COE) and Pierce County. Applications for a COE Section 404 permit must be made directly with the Corps.

At the State level, work within 200 feet of most rivers, lakes and creeks requires a Shorelines permit from the Washington State Department of Ecology (DOE). Water diversions are also controlled by DOE. The Department of Fisheries is charged with the preservation of fishery resources, and a Hydraulic Project Approval application (HPA) must be approved by Fisheries before work in a fish-bearing stream begins.

Most requirements, including Shorelines and the State Environmental Policy Act, are enforced by the local jurisdictions, usually during the permit application process. Local ordinances also control activities such as grading and filling within floodplains and wetlands.

Developing the Floodplain

Floodplain areas are ideally suited for recreational and agricultural uses. Limiting the amount of permanent improvements which may be damaged during a flood, such as homes and commercial developments, is preferred. Building is permitted in most floodplains, but structures must be elevated above the 100-year flood elevation. No permanent structures are allowed in designated floodways. Other uses such as gravel removal and water diversion for irrigation are strictly regulated.

Although large areas of natural floodplain are protected by a levee system, property owners should not rely solely on the existing levees to protect their property from all flood events. Few of the levees are considered adequate to contain a 100-year flood; however, larger floods or a levee failure can quickly overwhelm an area that was considered 'safe.'

Water Words

100-YEAR FLOOD ---- The flooding resulting from a storm which has a 1% chance of occurring in any given year.

FLOODPLAIN ---- An area which is covered by water during a flood, i.e. 'the 100-year floodplain.' Development within this area is regulated. The floodplain may also be considered a 'floodway'.

FLOODWAY ---- The main river channel and surrounding area which is needed to convey the flood flows. No filling or development is allowed in the floodway.

LEVEE ---- A flood-control facility designed to protect an area from flooding. Levees are often rated by the 'level of protection' they offer.

REVETMENT ---- A flood-control facility which reduces erosion along a riverbank and may act as a levee during smaller floods.

Floodplain Preparedness Information