In 1918–1921, one dam built on California's Carmel River provided water storage but blocked fish runs; in 2015 it came down, reopening 25 miles of habitat for steelhead trout

For nearly a century, a 106-foot concrete barrier kept one of California’s most resilient fish from reaching its spawning grounds. Crews began rerouting the river in the summer of 2013, and over roughly two and a half years, finishing in November 2015, they dismantled the dam piece by piece. A 2023 study titled ‘Six years of fluvial response to a large dam removal on the Carmel River, California, USA’ published in Earth Surface Processes and Landforms tracked the river for eight years, six of them after dam removal, and found that the dam removal did not trigger major downstream damage.

A dam built for growth, not for fish

The San Clemente Dam was constructed by Samuel Morse’s Del Monte Properties Company between 1918 and 1921 to provide water to the expanding Monterey Peninsula. It did that job for decades, but it was never good at allowing fish through. The 106-foot-tall dam sat at the confluence of the Carmel River and San Clemente Creek, blocking access to about 25 miles of upstream spawning habitat for steelhead trout, which migrate to the ocean and back to freshwater to spawn. KQED reported that the project has seen steelhead numbers on the Carmel River drop from about 1,350 fish in 1965 to just 249 in 2013, the last year the dam supplied water. The aging structure had been flagged as a serious earthquake risk by state dam safety regulators since the early 1990s.


Why it finally came down

By 2002, KQED noted, the dam’s reservoir was already about 90 percent full of silt, leaving almost no space for storage. There was little point in repairing a dam that could no longer hold water and might fail in an earthquake. Retrofitting the structure would have cost an estimated 49 million dollars, the outlet reported, but tearing it down instead cost about 84 million dollars, since a retrofit would only have addressed the earthquake risk while leaving the sediment buildup and blocked fish passage unresolved.

Engineers couldn't just blow up the dam and let a century of trapped sediment wash downstream. That much loose rock and dirt, nearly 2.5 million cubic yards, could have buried homes and habitat below, as NOAA Fisheries explained. Beginning in the summer of 2013, crews rerouted half a mile of the Carmel River into the adjacent streambed of San Clemente Creek, redirecting the river's main flow around the old dam and reservoir site rather than through it, then dismantled the dam piece by piece over the three-year project NOAA describes. It was, at the time, the largest dam removal in California.

What the river did once it was free

California rivers often behave differently from those in the wetter Pacific Northwest. While consistent seasonal flows reshape the channel, the Carmel River's recovery has been episodic, fueled by occasional big storms. The 2023 study reported that a major flood roughly 14 to 15 months after the dam's removal pushed an estimated 49,000 tons of sediment downstream by the spring of 2017 alone, reshaping pools and gravel beds that fish rely on. The study found that total sediment released in the first four years after removal was about 97,000 tons, less than many scientists expected because much of the old reservoir sediment had been intentionally stabilized in place. The same study found that floods carried that sediment more than 30 kilometers to the river mouth over two years, scouring the riverbed without major long-term downstream damage. The study authors conclude that taking out a big dam doesn't have to mean major reshaping of the channel below it.

The fish come home

The most significant finding was what was found in the water. NOAA Fisheries says the removal of the dam reconnected 25 miles of spawning and rearing habitat for South-Central California coast steelhead, a distinct population that has been listed as threatened under the Endangered Species Act since 2006. The agency has also credited the project with benefiting other wildlife in the river, including the federally protected California red-legged frog and Pacific lamprey, both species that hadn't been seen above the dam site since it was built, and both of which have since returned. The entire 25-mile stretch will not fully recover overnight, but every year of monitoring since 2015 has shown the same thing: native fish and wildlife moving further upstream into water that had been closed to their ancestors for generations.

Why this matters beyond one river

The Carmel River story offers a useful lesson as aging, unsafe dams across the U.S. reach the end of their useful lives; more than 80 dams were removed nationwide in 2019 alone, according to dam-removal tracking cited by restoration groups. Removing an old dam does not necessarily cause major downstream damage. If done carefully, with the sediment managed rather than dumped all at once, it can give a river, and every species that depends on it, a real second chance. Anyone who's ever wondered whether tearing down old infrastructure is worth the cost has a pretty clear answer flowing through the Carmel River right now.