Interactive

Hydrographic Survey for Riverbed Erosion

U.S. Geological Survey were out on the Missouri River at Williston, North Dakota, USA, performing a hydrographic survey to monitor the state of riverbed erosion. They were using a multibeam echo sounder which transmits sound energy and analyzes the return signal (echo) that has bounced off the riverbed or other objects. Multibeam sonars emit sound waves from directly beneath a ship's hull to produce fan-shaped coverage of the riverbed. 

Gage height at the Williston gage was approximately 27.65 feet when this video was taken. Additional information about the USGS streamgage at Williston is available at http://waterdata.usgs.gov/nd/nwis?program=nwisman&site_no=06330000