Hydrologist wants study of grit stirred up by boats on Kenai

Posted: Tuesday, March 14, 2000

KENAI (AP) -- Boat wake studies planned for the Kenai River may include an added dimension -- studies of how much sediment is stirred up by river craft -- if a federal hydrologist's recommendations are followed.

Lance Trasky of the Alaska Department of Fish and Game said adding turbidity studies could shed important light on the effects of wakes on riverbanks and habitat.

The Army Corps of Engineers already plans work on Johnson Lake and the Kenai River this summer to determine how changes in hull configuration, horsepower and loading affect the size of wakes. Previous studies have linked wakes to riverbank erosion.

The Corps will pay for half of its $120,000 study, and the state will pay the rest from $120,000 the Legislature appropriated to study both wakes and crowding on the river.

Last week, U.S. Geological Survey hydrologist Janet Curran proposed measuring turbidity, too, when the Corps does its work on the river. The measurements would cost about $20,000, with analysis and a report adding about $35,000 more.

Curran said wakes can increase turbidity by stirring up sediment already on the river bottom or by eroding new sediment from the banks. Her study would determine how much turbidity boat wakes stir up. Experiments to determine the impacts on fish would be the next logical step, she said.

Gary Liepitz, a Fish and Game habitat biologist, said some turbidity gives cover from predators, but too much could make it difficult for young fish to find food. The effects on fish could be difficult to measure, though, since those would likely vary with species and location.

On Thursday, Chris Degernes, Kenai area superintendent for Alaska State Parks, asked the Kenai River Special Management Area advisory board to approve funding the turbidity study from the $120,000 state appropriation.

That would leave the crowding study high and dry, she said. However, it may still be possible to obtain funding for the crowding study from the federal Environmental Protection Agency.

The advisory board voted 10-4 to ask Fish and Game to add Curran's project to the wake study.

Douglas Vincent-Lang, a state management biologist, said he wanted to consult the legislators who pushed for the appropriation before deciding on the wake study.

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