In the early days before the removal of the Glines Canyon and Elwha Dams that returned the Elwha River to its free-flowing state, most talk was focused on the return of salmon to a once-prodigious Native fishery. Some raised valid concerns about the post-removal turbidity as decades of sedimentary buildup behind the dams washed down to the sea: making the river water too cloudy for hatchery fish to survive in outbound migration much less the return spawning trip from the sea.
Eventually — in a decade or more, Dr. Warrick said — all of the sediment that had accumulated behind the dams will be gone. Then, the researchers predict, the river will revert to its pre-dam pattern, moving about 300,000 cubic yards of sediment downstream each year to the beaches.
Though the geology of California differs from that of the Pacific Northwest, Dr. Warrick said, this project demonstrates that dam removal may remedy beach erosion in both regions.
The idea is popular among some environmental lawyers and legal scholars who have long argued that beaches have “sand rights” — a right to sand that would naturally flow to them if people and their infrastructure had not gotten in the way. Advocates of sand rights say anyone who interferes with the flow of sediment to and along the shoreline should be required to mitigate the effects.
Once the water levels had gone down behind these dams the amount of sedimentary infill in these impoundment lakes was fully revealed. The entire contour of the valleys where the lakes had been had slowly filled up with sand, silt, and gravel. Deprived of their source of natural replenishment beaches and wetlands downstream had become anemic, requiring bolstering with rip-rap or other artificial means (as the law of unintended consequences rears its head). Reconnected with a century of undelivered sediment, the beaches at the mouth of the Elwha and nearby along the Strait of Juan de Fuca are rebounding at a reassuring rate as the turbidity of the Elwha’s waters continues to improve.
Read the full New York Times article from July 15, 2015 here.