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Title: Shoaling rates and related data from Knik Arm near Anchorage, Alaska
Authors: Everts, Craig H.
Moore, Harlan E.
Keywords: Sediments (Geology)
Publisher: Coastal Engineering Research Center (U.S.)
Series/Report no.: Technical Paper;no. 76-1
Abstract: Abstract: In high tidal range areas where large quantities of fine-grained sediment are carried in suspension, the potential for harbor shoaling is great. Because of high current speeds resulting from the tides, and because of winter ice conditions, many small-craft harbors in Alaska are constructed as enclosed basins connected to estuaries by a navigation channel. Such harbors, as typified by Dillingham Harbor where the shoaling rate is 6 feet per year, become sediment traps. This study measured summer shoaling rates in 1971 and 1972 in a sedimentation tank located on a tidal flat near Anchorage, Alaska. The mean shoaling rate was 0.073 foot per day in 1971, and 0.06 foot per day, or 15 percent less in 1972. Shoaling rates were uniform throughout the summer tests; the sediment surface in the 12-foot-diameter tank remained level. The accretion rate in the tank was 10 times as great as the rate on the adjacent tidal flat. Bulk density in the tank increased nonlinearly from the depositional surface to the bottom. The mass accretion rate was about 1.9 pounds per square foot per tidal cycle in 1971 and 1.6 pounds per square foot per tidal cycle in 1972. the mean particle size was 0.0058 millimeter in 1971, and 0.0068 millimeter in 1972. Size varied daily, but not at different collection stations in the tank. Vertical and horizontal circulation in the tank was not observed. Data concerning the characteristics of the fluid and sediment, the suspended sediment concentrations inside and outside the basin, and current velocities near the basin were obtained.
Description: Technical Paper
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Technical Paper

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