[Posted by Chuck Almdale]

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Why Dam Removal Matters for California’s Wildlife

Author: Judi Uthus, Public Engagement Specialist, California Trout
juthus@caltrout.org

California has thousands of public and private dams, ranging from small earthen structures to massive reservoirs rising hundreds of feet high. Built largely during the early 20th century, these dams were once considered engineering feats providing electricity, water storage, and flood control. Today, however, many have exceeded their intended lifespans and are part of a rapidly aging infrastructure. Research from the UC Davis Center for Watershed Sciences shows that dams also come with significant environmental costs–degrading watershed ecosystems, harming wildlife populations, and even posing risks to public safety. As a result, the ecological and economic benefits of removing outdated dams outweigh the costs of keeping them in place.

Nowhere is this more evident than with the sharp decline of anadromous salmon and steelhead populations. For decades, dams and other barriers have fragmented aquatic migration corridors, preventing fish from reaching the spawning grounds they depend on for survival. Southern California steelhead were once abundant in local rivers and served as a keystone species across the Santa Monica Mountains, holding deep cultural significance for local tribes. Although federally listed as endangered since 1997, their numbers have continued to fall, prompting California Department of Fish & Wildlife to add the species to its own endangered list in 2024 for additional protection. Restoring free‑flowing waterways is now considered essential to ensuring the survival and recovery of this iconic species.

California Trout, Southern Steelhead page link.

Rainbow Trout Oncorhynchus mykiss is a species of trout native to cold-water tributaries of the Pacific Ocean, found from the mouth of the Amur River in Siberia to Rio Baluarte in the Mexican states of Sinaloa and Durango.
Coastal Rainbow Trout Oncorhynchus mykiss irideus ranges from the Aleutian Islands in Alaska south to Southern California.
Southern California Steelhead is an anadromous (born in fresh water, migrates to sea, returns to freshwater to spawn) form of Coastal Rainbow Trout.
Scientific Name: Oncorhynchus: “hooked snout.” mykiss: Kamchatkan name for rainbow trout. irideus: “rainbow-colored” or “iridescent.”

The Malibu Creek Ecosystem Restoration Project 

One local dam impacting the Santa Monica Mountains is in the process of removal. Located three miles upstream from the Pacific Ocean in Malibu Creek State Park, is the 100-year-old Rindge Dam. Built in 1924 – 26 by Malibu’s Rindge family, the dam filled up with sediment by 1947 and abandoned in 1967. For over a century, the 100-foot-tall concrete wall has been an insurmountable barrier for local wildlife, particularly, for southern steelhead that cannot get upstream to their ancestral breeding grounds. Rindge Dam has also prevented 800,000 cubic yards of natural sediment from flowing downstream to replenish Santa Monica Bay beaches.

After two decades of study by the U.S. Army Corps of Engineers, the Malibu Creek Ecosystem Restoration Project (MCERP) has entered into the pre‑construction, engineering, and design phase. California State Parks (State Parks) is leading a team of consultants, stakeholders, and Tribal partners to determine how best to remove the dam, manage the trapped sediment, and address eight additional upstream barriers to fully reconnect the 18‑mile waterway.

“The removal of the dam will not only support habitat restoration and species recovery but also creates opportunities to reuse the sediment trapped behind the dam to nourish local beaches. This is sediment that would have naturally made its way to the coast if the dam had not blocked it. Additionally, by repurposing the material and avoiding landfill disposal, we anticipate significant cost savings for the project,” said R.J. Van Sant, project lead for State Parks.

Slated for completion in 2035, the MCERP will restore a key watershed and wildlife corridor of the Santa Monica Mountains. This restoration effort is expected to help not only southern California steelhead return to their native waters, but also benefit the populations of western snowy plovers, California least terns and least Bell’s vireo among many other species in this remarkably biodiverse watershed that is largely under public ownership.

Community Science Program

With a landscape-scale restoration project taking place within urban Los Angeles, the MCERP provides exciting opportunities for public outreach and education on protecting urban rural environments. CalTrout is leading a public engagement effort that includes both online and in-person engagement, including a Community Science Program.  Along Malibu Creek are seven photo monitoring sites where the public can help capture the changing physical conditions during the watershed’s transformation. This documentation will help establish a robust database throughout the restoration process and continuing stewardship of the watershed. 

A photo monitoring site is at Malibu Lagoon State Beach. The lagoon’s critical habitat will be shaped by the reconnection of a more natural supply of sediment from the upper watershed. The monitoring site located on the boardwalk overlooking the lagoon captures the shifting open and closed conditions of the lagoon, changes in habitat shapes, and the more dynamic natural processes as a normal creek flow becomes reestablished.

How do we know dam removal is worth the investment? With the removal of four dams along the Klamath River in 2024, the monitoring results just after one year show thousands of Chinook salmon pushing deep into newly reopened habitat—some reaching more than 360 river miles from the ocean into their Upper Klamath Basin breeding ground for the first time in over a century.

To learn more about the Malibu Creek Restoration Project and the Community Science Program, visit restoremalibucreek.org.

Illustration Caption:
Southern California rivers are naturally dynamic environments. Over eons, southern California Steelhead evolved an incredible ability to take advantage of the shifting habitat present in these rivers. Southern steelhead are anadromous fish – a fish that is born in fresh water, matures in the ocean, and returns to fresh water to spawn. Unlike Salmon, Steelhead spawn more than once in their lifetime. Their survival depends on a web of interconnected aquatic ecosystems. Because of this, they are the best indicator of watershed health. The interplay of habitat type, habitat condition, and the connectivity between habitats over time is paramount in their development and survival in the coastal watersheds of Southern California.