A branch of surveying which deals with any body of still or running water such as a lake, harbor, stream or river, hydrographic surveys are used to define shore line and underwater features. Surveyors operate in nearly any body of water, from the shallowest of waters, lakes, bays, to riverine environments.
Reasons for a Hydrographic Survey:
- Habitat restoration
- Tidal measurement as it affects sea defense works
- Determination of direction and flow of current in connection with flood plain or construction interests
Hydrographic Mapping of the Multnomah Channel
SWLS provided services to ESA for the hydrographic mapping of the Multnomah Channel near the south tip of Sauvie Island. The objective of the project was to provide information to help with the restoration of Miller Creek to its original path. The hydrographic portion of the survey supplemented the land survey topography mapping.
On this survey, our 16’ shallow water sled was used with a Trimble RTK GPS. The Hydrolite sonar unit was also used, streaming depth values into a TSC3 data collector at a rate of 2 Hz. The depths were then subtracted from the RTK X, Y, and Z position of the transducer. A bar check was performed two times a day to adjust the sound velocity in the sonar measurements.
Other Statewide Hydrographic Survey Projects
Columbia River Estuary Task Force (CREST) – Clatskanie River, Clatsop County, Oregon
Mt Hood Environmental – Early Winters Creek, Okanagon, Washington
Pacific Northwest National Laboratory – Grays River, Grays River, Washington
Cascade Environmental Group – Youngs Bay / Wallooski River, Clatsop County, Oregon
USACE Portland District – Willametter Valley Flood Study, Oregon