Topline:
L.A. County Public Works has removed more than 90,000 cubic yards — the equivalent of 27 Olympic pools — of sediment from Devil’s Gate Reservoir, one of 14 dams in the San Gabriel Mountains that prevent flooding and capture water for our drinking supply.
The context: You can see Devil’s Gate Reservoir while driving west on the 210, just below NASA’s Jet Propulsion Lab. The dam helps prevent flooding downstream in communities such as Pasadena and others along the Arroyo Seco. But since the 2009 Station fire — the largest fire recorded in L.A. County — the reservoir has been inundated with muddy sediment. Since 2019, more than a million cubic yards of sediment have been removed from the reservoir.
Why it matters: More sediment in reservoirs means less room for more water, so there’s a higher risk of flooding when big storms hit — and this winter is expected to be another wet one. More sediment in reservoirs is a mounting challenge for water supply and flood safety because the climate crisis is driving bigger fires and bigger floods.
What’s next: The county has faced challenges in getting enough funding to maintain sediment-inundated dams. In June, the county received funding to remove sediment and fortify the Santa Anita Dam, one of the largest dams in the county. The county estimates that across its 14 dams, some 15 million cubic yards of sediment needs to be removed.
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