How to Restore a Beach, Naturally
By Cassandra Beeler
Damming of water has been a major problem for sand getting to the coast. Before all these dams were created, LA had enough extra sand to send to Waikiki!
Beaches are a natural defense from coastal storms and rising sea levels and provide essential habitat for native and migratory species. Our coastlines now hold over 40% of the US population, with beaches as a $520 billion economic asset to the US economy.
America’s beach systems are naturally dynamic, shifting with changes in climate, tidal activity, and sea level. The size and continued function of our shorelines depend on the amount of sand accreted or lost from eroding dunes, nearshore currents, and rivers.
As coastal development increased throughout the 20th century, followed by a surge in dam construction in the 1950’s, America’s shorelines started losing the ability to naturally shift and regrow. Navigation inlets and jetties that supported the growing coastal population disrupted the sand travelling down the coast; the rivers that delivered sediment to shorelines for centuries were dammed. Some beaches grew. But more shrank.
Our beaches now face chronic erosion, relying on humans to rebuild natural conditions with beach nourishment and armor with sea walls and groins. But is there a way to restore the once-natural sand replenishment of beaches?
There are over 92,000 major dams in the US averaging 65 years old, with almost 30,000 dams posing a significant or high hazard risk. Advocacy groups and local stakeholders argue for the decommissioning of aging dams, noting impacts to water quality, migratory fish, local watersheds, and public safety.
However, this negative impact can also span miles, even states, away. Hundreds of thousands of cubic yards of sediment are unable to reach downstream shorelines, with two-thirds of the sediment that used to end up on our coasts trapped inland. Take Washington’s Elwha River for example, where two dams have trapped 30 million tons of sediment since their construction in 1913 and 1927.
As dams are removed, careful management plans are in place to ensure excess sediment isn’t polluting or flooding surrounding areas. It takes years for the buildup to wash downstream, and much is deposited along the river basin. As the river returns to its natural state, it delivers sand to the coast and naturally replenishes sandy shorelines.
Removal of the Elwha and Glines Canyon dams began in 2011, and in the following 5 years, the river delivered 5.42 million tons of sediment to nearshore and estuarine environments. This grew the shoreline of the Elwha River Delta by approximately 600,000 square meters.
While this level of rapid sand deposition will eventually reach an equilibrium, the coastline will continue to receive sediment from the Elwha River. This poses the question: Can dam removal be a natural solution to our sand-starved coasts?
Nevertheless, with over 90,000 major dams in the US, this can’t be the only solution. While dam removal could be a remedy for certain eroded beaches, not all will be removed simultaneously, or quickly enough to see real change in sediment dispersal. Further, as global and sea surface temperatures continue to rise, original sediment delivery may still not be enough to combat rising sea levels, flooding, and extreme weather.
Pairing the restoration of sediment transport processes, like dam removal, with innovative, nature-based solutions, like living shorelines and beneficial reuse of dredged material, is essential to planning not just for our sand-starved beaches today, but well into the future.
