129 



dams are not very effective for flood control ( they can store only 7% of the 

 mean annual runoff), we still get flooding; the erosion end of the beach cycle is 

 still alive and well. The deposition end, however, is ill. The flood waters are 

 relatively free of the large sediment that forms beaches; we call this clear water 

 flooding. Some sand is still recruited from the river's tributaries below the dam, 

 especially the Imnaha and Salmon Rivers, but this is a fraction of that which 

 once came down the Snake. 



Geologists Grams and Schmidt pubHshed the most comprehensive study of 

 Hells Canyon beach erosion done to date in 1991, after reviewing changes in 

 beaches from 1955 to 1990. They foimd the number and size of beaches 

 reduced by 75% following construction of the dams, and attributed the loss to 

 clear water flooding. When asked what role boat wakes played in the loss, they 

 replied that it was insignificant. 



According to a U.S. Army Corps of Engineers study in 1976, twenty years 

 ago, beaches, gravel and mud bars made up about 1% of the shoreline in Hells 

 Canyon. The Forest Service, in their EIS felt this figure might have been low, 

 but still guessed the percentage at less than 5%. The balance of the canyon's 

 shoreline is armored with rock. 



A monitoring study was done by the Forest Service in 1993. Surprising no 

 one, they found that boat wakes moved sand near the water's edge. Sometimes 

 they found an increase of sand in their transects and sometimes a decrease. In 

 either case the sand was not being moved very far. However, when the floods 

 cover the bars, this micro movement caused by wakes becomes moot. It 

 matters not one scintilla in the broad picture of beach dynamics. If ever there 

 was a river where the effects of power boat wakes on the shoreline are nil. Hells 

 Canyon, with its rocky shores, is it! 

 Noise and Speed 



Jet boats roar up and down the river with their 900 horsepower engines at 60 

 to 100 miles per hour. This is the tongue-in-cheek way our opponents try to 

 typify river running jet boats. This description might fit the race boats 

 sometimes seen on television at competitive events, but these are not the boats 

 used for recreation in Hells Canyon. In fact, use of this type of craft is now 

 prohibited by state laws without a special event permit, and the Forest Service 

 has prohibited such events on wild and scenic rivers. Both the states of Idaho 

 and Oregon have set limits on the amount of noise boats are allowed to make. 

 The Forest Service already prohibits over-the-transom manifolds in the 

 HC^fRA and requires mufflers, effectively eliminating the drag and race boats. 



In June, 1991, Rob Harrison and Bill Makel from the Forest Service 

 Technology and Development Center at San Dimas, California took a quick 

 look at the boat-sound situation in Hells Canyon, traveling the river and 



15 



