Use of slope creation for rehabilitating incised , 3 regulated , gravel bed rivers 4

6 [1] Gravel-bedded channels often become incised and degraded below dams. Gravel can 7 be added to the channel to rehabilitate hydrogeomorphic conditions, including those 8 promoting salmon spawning. When implemented without increasing bed slope, gravel 9 addition at downstream riffles back floods upstream riffles. A 2-year gravel augmentation 10 project was done to test the efficacy of a new method for ‘‘slope creation.’’ 11 Riffle-to-riffle slope was raised from 0.002 to 0.008 by adding gravel to the most upstream 12 riffle. When gravel was added to the next downstream riffle a year later, riffle-to-riffle 13 slope decreased to the sought after 0.004. After the study, the area of high-quality 14 Chinook salmon spawning habitat increased 471%. The number of redds observed went 15 from 62 to 161 during the study despite a 50% decline of in-river spawners. This 16 eliminates variations in migrant population size and hatchery take as alternative 17 explanations. Slope creation can be a useful aid for rehabilitating regulated rivers.