The vertical plane of reference is adopted low water. Tidal range at Vancouver is about 3 feet and about 0.2 feet at Bonneville  during low river stages. Extreme tidal ranges are about 4 and 0.4 feet, respectively. Annual freshets average about 12 feet at Vancouver, while the highest known reached a stage of 33 feet.

The majority of shoaling in the Columbia River occurs during the period immediately following the annual freshet in early summer. The dredge YAQUINA is brought in to remove shoals before low water levels in the fall.

Many shoals in the Columbia River are called sand waves, which look like giant versions of sand ripples that form as waves recede at the beach. In this project, sand waves along the river bottom are often 4 to 8 feet high and up to 300 feet long. In some river reaches, the dredge removes up to 2 feet of advanced maintenance dredging below the authorized channel depth so that shoaling builds below authorized depth during the next freshet and does not restrict commercial barge traffic.

Advanced maintenance width dredging is also practiced up to 100 feet outside the authorized channel width in locations where heavy shoals encroach from the sides. During the past 2 years, minimum maintenance dredging has averaged just over 100,000 cubic yards per year. Dredged material is placed at in-water sites.

Authorized channel is 27 feet deep and generally 300 feet wide from Vancouver, Wash., Columbia River Mile (CRM) 106.5, to The Dalles, Ore., CRM 189.7.

The channel is presently maintained to 17 feet for barge traffic. An additional barge channel, 15 feet deep and 300 feet wide, from under the wide, fixed span of the Interstate Bridge connects to the main channel about 7,500 feet upstream. An alternate barge channel 17 feet deep and 200 feet wide, under the high, fixed span of the Interstate Bridge, transitioning to 300 feet wide, connects to the main channel about 8,000 feet upstream.

There is a turning basin at Camas-Washougal, Wash., CRM 121.6.

• Channel at the upstream entrance to Oregon Slough, 10 feet deep by 300 feet wide, and approximately 5,800 feet long from Oregon Slough River Mile 5.8 to deep water in the Columbia River at approximately CRM 109.
• Small boat recreational channel 6 feet deep and 100 feet wide, connected with the main channel, between CRM 110.8 and 118.4 on the South side of Government Island.
• Access channel to Hood River Boat Basin, 10 feet deep from deep water in the Columbia River, at approximately CRM 169.
• Barge channel to the waterfront at Bingen, WA, 10 feet deep, 200 feet wide, and approximately 1 mile long, connected with deep water in the Columbia River at approximately CRM 171 and 172. There is also an access channel from the upstream end of the barge channel to a natural mooring basin for small boats, 7 feet deep, 100 feet wide, and approximately 1,000 feet long.

Boat basin at Hood River, Ore., at approximately CRM 169, 10 feet deep by 500 feet by 1,300 feet. Constructed rubble mound east breakwater.

The Dalles Harbor, Ore, at approximately CRM 189, 8 feet deep by 400 feet by 800 feet. Constructed pile, timber, and stone breakwater, 900 feet long, and a shear boom.

The Rivers and Harbors Acts of: Aug. 26, 1937, March 2, 1945, and July 24, 1946.

Section 107 of the Rivers and Harbors Act of 1960 provides authority for the Corps of Engineers to develop and construct small navigation projects. Projects authorized under Section 107 were approved in Oct 1962 and July 1983.

The Energy and Water Development Act of Aug. 17, 1991, and the Water Resources Development Act of Aug. 17, 1999.