Thursday, July 11, 2013

San Clemente Dam has deprived the lower river of sediments and for almost 100 years

The San Clemente Dam has retained 2.5 million cubic yards of bedload and  large woody debris since its construction, depriving the lower river of  sediments and for almost 100 years. Rivers that have been deprived of natural sediment inputs from upstream of dam sites often compensate by eroding sediments from the lower floodplain below the dam. 

Armoring along the river has been, and still is, used to combat the sediment starved reaches of the river from eroding banks and widening the river valley. Up to 40% of the river’s banks from the mouth to Rosie’s Bridge have been artificially hardened to protect infrastructure from erosion. Hardened banks  have prevented sufficient compensational erosion from taking place in the lower floodplain, causing the river to degrade and narrow.

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