Shorelands, wetlands and floodplains associated with Shorelines of the State

The land areas bordering shorelines of the state that are under jurisdiction of the Shoreline Management Act are called "shorelands." The Act defines a minimum geographic area and also provides local government options to include a greater area within its shoreline master program.

Shorelands | Wetlands | Floodplains


Shorelands include those lands extending landward 200 feet in all directions as measured on a horizontal plane from the ordinary high water mark (OHWM).

On rivers, the shoreland area includes the entire floodway and contiguous flood plain areas landward 200 feet from the floodway.

Associated wetlands

All wetlands which are in proximity to and either influence or are influenced by tidal waters or a lake or stream subject to the Shoreline Management Act are considered associated wetlands.

River deltas associated with shorelines of the state are also considered associated, except for those lands protected from floodwaters by authorized flood control devices. Deltas are created at the mouth of a river where it enters a larger waterbody.

The entire wetland is associated if any part of it lies within the area 200 feet from either the ordinary high water mark or floodway.

Factors used to determine whether wetlands meet the "proximity and influence" test include but are not limited to one or more of the following:
  • Periodic inundation
  • Hydraulic continuity
  • On marine waters: formation by tidally influenced geohydraulic processes; or a surface connection through a culvert or tide gate
  • On streams: the entire wetland is associated if any part is located within the 100 year floodplain of a shoreline.

Consider all factors together when determining association.

A wetland's hydrology does not have to be in a defined channel to be considered associated. Hydraulic continuity clues include undrained hydric soils continuous with the waterbody, and sheet flow from the site during or following precipitation events.

In some cases wetlands outside the 100-year floodplain may be associated if they are hydraulically connected with shoreline waters through surface or subsurface flows.

In coastal systems, all wetlands behind the primary dune are associated with the larger water body, i.e. ocean, bay, etc. Wetlands behind the second dune must have direct hydrologic (surface) connection or be part of a continuum of associated wetlands to be associated.

A road, dike or other barrier between the shoreline and the wetland does not necessarily preclude hydraulic continuity.

If there is an obvious topographic break from the elevation of the waterbody (excluding natural or man-made berms), the wetland is probably not associated.

Optional area: 100-year floodplain

Local government may, at its discretion, include all or a larger portion of the one hundred-year floodplain within shoreline jurisdiction, as long as such portion includes, as a minimum, the floodway and the adjacent land extending landward two hundred feet from the floodway boundary.

When updating an SMP, local governments now have the option to include in SMP jurisdiction the buffer needed to protect associated wetlands.

If a local government exercises this option, the buffers for critical areas would be considered within jurisdiction regardless of whether the buffer zone is in the floodplain.

Note: the legislature stipulated that forest practices regulated under the Forest Practices Act (RCW 76.09) are not subject to additional shoreline regulations on lands subject to any expanded buffer zones. This exemption only applies to forest practices and does not apply to shoreline regulations addressing conversions to nonforest land use.


For more information

Back to Top