Exploring California’s Marine Protected Areas: Big River Estuary State Marine Conservation Area

Big River Estuary SMCA
Kayaker at Big River Estuary State Marine Conservation Area
photo by L. Kashiwada

Big River Estuary State Marine Conservation Area (SMCA) is a small marine protected area located just south of the town of Mendocino. It covers less than a quarter square mile of estuary habitat along 1.3 miles of riverbank east of the Highway 1 bridge. Though it may be small, the impact of Big River Estuary SMCA on Mendocino Coast inhabitants has been profound.

Big River Estuary State Marine Conservation Area (click to enlarge)
map by CDFW Marine Region GIS Lab

When Bill Lemos and Robert Jamgochian, two teachers at Mendocino High School, started the School of Natural Resources (SONAR) program in 1999 with a small state grant, nearby Big River Estuary was a natural focus for the program. At the time, the teachers had no idea that the estuary information collected as part of the SONAR program would be instrumental in the preservation of over 7,300 acres of forest land in the lower Big River watershed, and contribute to the establishment of the Big River Estuary SMCA in 2012.

The survey information that helped to establish Big River Estuary SMCA was collected by young, eager students with well-trained minds. Environmental scientists and biologists from the California Department of Fish and Wildlife, State Parks, and Campbell Timber Management Company taught SONAR students to conduct scientific surveys and identify different species of fish, birds, and invertebrates. Students began conducting surveys in 2001 under the watchful eyes of their teachers and professional mentors, and successive classes (and teachers) continue to survey the river to this day.

SONAR students categorized and enumerated the incredible variety of life in the lower eight miles of the river, including rare and endangered species like coho salmon. Students also documented the damage caused by timber harvesting, especially the increased sedimentation due to logging activity that has filled in more than half of the tidal estuary since the 1890s.

Bountiful Big River started “Red Gold Rush”

As part of their studies, SONAR students learned about the wreck of the clipper ship Frolic, which struck a reef north of Big River in 1850. The ship-owner’s agent who was sent up the coast to investigate the wreck found little of the ship’s cargo to salvage, but reported that vast, accessible tracts of redwood trees bordered Big River. These stories led lumber merchant Henry Meigs to order a sawmill that was delivered by boat to the mouth of Big River, and started a “red gold rush” along the entire Mendocino coast.

Big River Mill
The third Mendocino Lumber Company Mill, located on the river-flat; photo taken between 1894 and 1906.
Photo © Bancroft Library, University of California, Berkeley

Meigs’ steam-powered sawmill, the first built in the area, was assembled on the bluffs overlooking Big River in 1852. One year later, a second, larger sawmill was built on Big River Flat itself, in what was to become Big River Estuary SMCA. Together these two mills produced up to 100,000 board feet of lumber per day.

Big River was a hot spot for logging redwood trees on the Mendocino coast. Ox teams and, later, steam-powered trains called “steam donkeys” pulled the logs to the river to be floated downstream to the mills. Since Big River was usually not deep enough to float logs, numerous dams were built throughout the watershed to catch rainfall and increase the water depth. Once rain and river water filled the area behind the dams, they were opened in sequence (many just blasted apart) to create enough waterhead to float the logs downstream. Often an entire year’s worth of logs was moved down to the estuary in one big, artificial flood, or “swamping.”

This kind of logging and river transport scoured the channels and riverbanks and changed the landscape. Water channels that used to support innumerable salmon, steelhead, and other fish were ground clean, and sediment clogged the lower reaches of the river, especially the estuary. The logs were retained in the estuary by booms until they were milled, which made it difficult for the native flora and fauna to survive in the estuary.

Big River Mill, photo taken between 1920 and 1938.
photo © Dot Johnson – Kelley House Museum, all rights reserved

A succession of lumber mills were built on Big River Flat over the years, with the last mill closing permanently in 1938. The only visible remains of the mills and logging activity today are old wooden pilings on both sides of the estuary, remnants of the rough water barricade, boom sticks used to keep logs out of the mud flats, and wedge-shaped wing dams that directed logs to the mill.

From the late 1970s through the early 1980s, the salvaging of “sinkers” (old growth logs that had sunk into the mud) again damaged the riverbed. Nevertheless, the river and estuary slowly healed from the extractive logging activity, and the extraordinary diversity of life documented by SONAR students once again began to flourish.

In the late 1990s, Mendocino Lumber Company filed plans to engage in large-scale timber harvesting in the Big River watershed. When local activists, including current and former students from Mendocino High School, heard of the plans, they organized a national campaign and used the SONAR survey data to persuade state agencies that the watershed should be protected. The campaign resulted in the purchase and transfer of over 7,300 acres (the Big River unit) to State Parks in 2002, establishing park lands on either side of the river. SONAR survey information was also used to help establish Big River Estuary SMCA in 2012.

On the Mend

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Logging still occurs on over one hundred thousand acres of timber lands in the Big River watershed. Although the river and estuary are no longer used to transport logs, sediment associated with logging practices still washes into the river (and is monitored by State Parks).

Despite the ongoing logging activity, eelgrass beds have re-established along the banks of the lower reaches of the river, providing essential habitat for fish and invertebrates. Perch are the most abundant type of fish in the estuary, with seven species found there. Other native fish include coho salmon, Chinook salmon, steelhead trout, Pacific lamprey, sculpin, three-spined stickleback, and Sacramento sucker. Pacific lamprey is a particularly important species, because its high fat content makes it a preferred prey item for animals that eat fish. Sportfishing for perch and Dungeness crab, and hunting for waterfowl is permitted in accordance with state fishing and hunting laws, but no other take is allowed in Big River Estuary SMCA.

Kayakers regularly spot playful river otters and harbor seals in the SMCA. Bird surveys show that a wide variety of fish-eating birds and waterfowl reside in or visit the Big River Estuary. Great blue heron have established a rookery in the trees overhanging the estuary, so these graceful fish-eating birds are a common sight. Kayakers have the best chance of seeing birds on the estuary, from ducks dabbling in the water to acrobatic osprey diving for fish, among the many species present. Bald eagles have also been seen soaring down the river, though they are a rare sight.

Lots to do in Big River Estuary SMCA!

Look for the Mendocino Headlands/Big River Beach sign at the Highway 1 overcrossing to access Big River Estuary SMCA.
photo by L. Kashiwada

The western border of Big River Estuary SMCA starts at the Highway 1 bridge and runs about 1.3 miles eastward and inland. State Park lands (the Big River unit of Mendocino Headlands State Park) run along the river and extend much farther inland, beyond the SMCA.

Some of the most popular activities in Big River Estuary SMCA are kayaking, stand-up paddle boarding, canoeing, and swimming. If you plan to paddle along the river, it is important to pay attention to the tides. Paddlers are advised to plan their trip so they are travelling upstream with the incoming tide and returning downstream with the outgoing tide. The offshore breeze often picks up in the afternoon, which can make returning downstream a challenge as well.

There are several launch areas along Big River Flat on the north side of the river, east of the Highway 1 bridge. To get there, turn onto Big River Road just north of the Highway 1 bridge. Park in the lot at the bottom of the hill or along the road for access to the beach. This is a wide beach, well-suited for gatherings, picnics, beach games, wading, and swimming. Dogs are allowed on this beach but must always be leashed.

Park at the end of the Big River Road for access to Big River Trail (the old logging haul road). This multi-use trail runs for over 10 miles on the high bank above the river. Motorized vehicles are not allowed on the trail. This is a day-use area only.

Big River Estuary State Marine Conservation Area is one of the 124 MPAs in California’s statewide MPA network. Please visit CDFW’s MPA website for more information, and sign up to receive updates about the MPA Management Program.

logo post by Leslie Kashiwada, CDFW Scientific Aid


Learn more about MPAs by diving into the
Exploring California’s Marine Protected Areas series!