RELATED ECOLOGY PROGRAMS
Ordinary high water mark
The ordinary high water mark (OHWM) as defined in the Shoreline Management Act (SMA) is a biological vegetation mark. Ecology's rules include a default tidal or fresh water elevation line for locations where the OHWM cannot be found.
The OHWM is defined as:
The position of the OHWM in relation to extreme high and extreme low water varies from site to site.
At any given site, the OHWM will vary over time and according to factors that include wind, waves, erosion, accretion, soils, substrates, vegetation, land use changes, runoff, groundwater, the presence of peat, the constancy of pool elevations, and the activities of beavers and other organisms.
Determining the Ordinary High Water Mark on Streams in Washington State - DRAFT (Ecology Publication #08-06-001)
For assistance with ordinary high water mark determinations, contact Ecology's regional planner assigned to your town, city or county.
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