A Coastal Perspective on Dam Removal

Elwha Dam Removal Photo credit: Kate Benkert (USFWS). Available at Flickr under a Creative Commons Attribution-NonCommercial 2.0
Overview map of the Elwha River watershed, and the former location of the Elwha and Glines Canyon dams. Map courtesy of Olympic National Park

The Elwha has become an ideal living laboratory for studying the nuanced functions of a large, natural coastal system.

As the debate about the removal of the two dams in the early 2000’s started to transition from “if” to “when” and “how”, I started to spend a lot of time down at the mouth of the Elwha River on a surf board, chasing after the phantom swells that ghost in from the Pacific Ocean through the narrow Strait of Juan de Fuca. The beach of the Elwha River delta was rapidly eroding, and surfing provided a front row seat for a show put on by a complex and changing coast. People wondered if the chronic erosion on the beach was related to the construction of the dams, and the sediment they trapped in their reservoirs. As I pondered the question, I was hooked. That question set the trajectory of my scientific career, and formed the core of my dissertation research focused on coastal sediment transport, with the shoreline around the Elwha River mouth as my laboratory.

Elwha Dam, before (top panel, September 2011) and after (bottom panel, May 2012) dam removal. Photos courtesy of Olympic National Park.
While deposition on the sea-floor wasn’t widespread, small areas near the river mouth were transformed. These are photos of the same location on the sea-floor from before (Summer 2011) and after (Summer 2017) dam removal. A surveyor’s tape laid down by SCUBA divers runs through both photos. While the image in the lower panel looks lifeless relative to the earlier 2011 photo, these sandy patches were quickly utilized by new species.
The river mouth of the Elwha River was transformed by dam removal. While the mud that made it to the coastal zone has largely moved out of the system, much of the sand and gravel deposited right near the river mouth during dam removal, and is still there. It built new beaches, estuary lagoons, and other shallow coastal habitats. The sea-floor was also transformed in patches right near the river mouth. The dots reference locations of photos shown above.



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