American White Pelicans Splash Down in Corte Madera

by Meryl Sundove and Roger D. Harris

A birding opportunity exists to see huge American white pelicans up close on the east side of Redwood Highway at Corte Madera Shorebird Marsh. Assemblages of up to three dozen pelicans congregate on the artificial islands in the lagoon and forage in the water there and at the nearby South Outfall Canal. Parking is at a pullout between Trader Joe’s and Nordstrom. Shorebird Marsh is part of the once more extensive marsh complex at the mouth of Corte Madera Creek.

Flocks of white pelicans visiting Shorebird Marsh and Corte Madera Creek have brought much-needed delight in these anxious times. Photo by Ann Thomas

American white pelicans are often seen feeding and roosting together in Marin between July and January, their nonbreeding season. Large numbers of nonbreeding pelicans also frequent California’s Central Valley. Migrating away from the San Francisco Bay Area, starting in late January, they are on their breeding grounds from February through May and part of June. The greatest numbers breed on brackish and sometimes freshwater lakes in the Great Basin and elsewhere in the interior of North America, where they nest in dense colonies in remote locations, free from human disturbance. Although monogamous, pair bonds are established upon arrival at the nesting colony, suggesting a repairing each year. Nest site tenacity—returning to the same nest location each year—is rare or absent.

These pelicans often feed cooperatively, swimming together in a coordinated, almost ballet-like fashion, to corral schooling fish towards the shallows, where they scoop them up in their large pouches before swallowing the catch. They are also known to steal fish from other birds, especially gulls and cormorants. This is known as kleptoparasitism.

Don’t just look on the water for white pelicans, but scan the skies too. You may see a magnificent squadron of these immense birds floating on high. They soar with a graceful steadiness on broad white and black wings. These pelicans move to and from roosting and feeding areas such as the marshes along Highway 37. Large heads and huge beaks make these pelicans look almost prehistoric, and they are one of North America’s largest bird species. They have the second largest wingspan of any bird in North America, after the California condor. Wingspan averages 95–120 inches and body weight ranges from 11 to 20 pounds. They are among the heaviest flying birds in the world. Males are generally larger than the females but otherwise the sexes look alike.

The American white pelican is listed as a California Species of Concern, which means a species at risk in California. They used to breed more widely in the state, but decades of declining numbers have left them breeding regularly in California only in the Klamath Basin and at Clear Lake. The main cause of decline is loss of habitat, often from water diversions and land reclamation for agriculture. Outside California, however, the species is common enough to qualify as a Species of Least Concern, according to the International Union for Conservation of Nature.

The full name for our species includes “American” to distinguish it from the great white pelican, which breeds in southeastern Europe, Asia, and Africa. The Old World pelican is enormous, with a wingspan reaching close to 12 feet. Our white pelican also differs from our other local pelican, the brown pelican, most obviously in its color. The American white pelican is also bigger. Like its larger relative, the brown pelican leaves the Bay Area for the breeding season, becoming scarcer around mid-February to mid-April. However, some nonbreeding birds linger in Marin all year. The breeding birds nest on the Channel Islands in Southern California.

While the American white pelican forages from the surface of the water, dipping its beak down into the water to scoop up prey to swallow, the brown pelican is a plunge diver. It patrols as high as 60 feet above the water, then plunges into the water. Its throat pouch expands to trap fish, filling with as much as two gallons of water. It then surfaces with its beak held close to its body, allowing water to drain out of the pouch, and swallows the prey with a toss of its head.

A wonderful bird is the pelican.
His beak can hold more than his belly can.
He can hold in his beak
Enough food for a week!
But I’ll be darned if I know how the hellican!

― Dixon Lanier Merritt

Land Sculpture: Creating a Marsh

by Ann Thomas

Walkers and cyclists on the multiuse path through the Corte Madera marshes are being treated to a view of the creation of a new tidal wetland, and of an improved trail system using dredge spoils from the 1950s. The project is on a four-acre portion of 72 acres east of Hwy 101 purchased by the Golden Gate Bridge, Highway and Transportation District in the 1970s as mitigation for habitat loss and damage caused by the district’s construction of the Larkspur Ferry Terminal.

The restoration, northeast of The Village shopping mall, is bordered on three sides by the California Department of Fish and Wildlife’s Corte Madera Ecological Reserve, and on the west side by a strip of land owned by the Sonoma Marin Area Rail Transit, a popular walkway through the marsh system.

Work began in October and is scheduled for completion by January 31 of 2021, to be followed by a four-month maintenance period. Some social trails, along with portions of berms that were constructed to contain dredge spoils, are being removed and parts of the area have been temporarily closed to the public.

The four-acre restoration is an obligation imposed on the transit district in return for permits it received in 1988 for dredge disposal and in 1996 for modifications in ferry use. In the intervening years the project site has been colonized by nonnative vegetation, becoming a haven for pampas grass and the homeless while restoration work was deferred.

To meet the permit requirements, the project is designed to provide tidal marsh habitat suitable for federally listed species including Ridgway’s rail and the salt marsh harvest mouse. Components include mudflats, low marsh, high marsh, and a transition zone with vegetative refugia suitable for these endangered species and other wildlife that use the marsh. The upland refugia would be fenced off from pedestrians and dogs that use the 25-foot-wide fenced public zone. The project also includes relocation of about a quarter-acre of seasonal wetlands within the project boundaries.

While work is proceeding on the restoration, 14 acres of the district’s property have been enclosed by orange fencing to keep the public safe. In late October through December visitors had daily views of bulldozers, water trucks, excavators and dump trucks excavating approximately 28,000 cubic yards of material to be reused onsite. Heavy equipment removed invasive vegetation and reshaped the four-acre project site, opening a new tidal channel on December 10 to the wetland site; excavated material was placed next to the wetland for upland habitat. Following this, 17,000 native plants are being installed, and the surrounding 10 acres hydroseeded with native seed.

Once the project is completed, visitors will be able to hike around the restored marsh on a new berm that will create a loop similar to the existing trail. Benches, trash cans, and interpretive signs are planned along the reconfigured loop trail that will be open to the public when construction is complete.

Tidal waters are being welcomed back to an area of former marsh, east of Hwy 101. Photo courtesy of GGBHTD

Come on in, the Water’s OK!

by Sandy Guldman

This spring, public swimming pools and beaches were closed, people were urged to stay home, and Corte Madera Creek looked very tempting on hot afternoons. The warm weather prompted a number of phone calls and emails to Friends with two questions: Are we allowed to swim in the creek? Is it safe to swim in the creek? The answer to the first questions is easy: do so at your own risk. The second question is more to the point. We replied that based on our most recent testing, about 15 years ago, swimming in the creek wasn’t recommended, but it is probably not dangerous to swim well downstream of Bon Air Bridge and at high tide, as long as you don’t swallow any water and take a shower after swimming in the creek.

Swimmers enjoy themselves in the High Canal behind Tamal Vista Blvd. The water here is probably less clean than in Corte Madera Creek where tidal flushing occurs twice daily. Photo by Sandy Guldman

Clean bay water, mostly from the ocean, flushes the system twice a day, keeping the water clean and safe for swimming. The less tidal exchange there is, the more bacteria the water is likely to contain. Note that we didn’t test water quality in the High Canal or Larkspur Creek, both of which are likely to be much more polluted than the main stem.

The keen public interest prompted us to consider testing again. We first checked with the Marin County Community Development Department, Environmental Health Services, which samples water weekly at beaches in Marin County. Although Corte Madera creek doesn’t have beaches, it is heavily used by rowers, paddle boarders, and swimmers. However, when we asked if they would consider adding a couple of sites on the creek, the answer was no.

Our next call was to Steve Moore, General Manager of Ross Valley Sanitary District, to ask if RVSD had a lab. He replied that RVSD sends samples to a lab at the Central Marin Sanitation Agency. Then Steve contacted Jason Dow, CMSA’s General Manger, to see if their lab would process samples from Corte Madera Creek for Friends at no charge. Jason agreed to do so. Friends bought some supplies, CMSA provides other supplies, and three of us started sampling at the end of August.

We take samples at docks in Piper Park and at the Marin Rowing Association. As soon as the City of Larkspur has repaired the public dock downstream of MRA, we can switch to that location. In the hope that Marin County might eventually add Corte Madera Creek to their testing program, we decided to follow their protocols. We collect samples once a week on Monday or Tuesday and deliver them to the CMSA lab. The County’s focus is on recreational use, so they sample April 1 through October 31. We got a late start, so we have data only for September and October.

The samples collected by Marin County are tested for Total Coliform, E. coli, and Enterococcus bacteria. Advisories are posted at a beach when a recreational standard for these indicator organisms is exceeded. Two samples are taken at each site; one is used for Total Coliform and E. coli, the second for Enterococci.

According to the EPA, Enterococci, a subgroup within the fecal streptococcus group, are distinguished by their ability to survive in saltwater. For that reason, the EPA recommends Enterococci as the best indicator of health risk in saltwater used for recreation and as a useful indicator in fresh water as well, and defines a testing methodology and a measurement unit of the number of colonies of bacteria that have grown under controlled conditions, expressed as the most probable number or MPN. EPA recommends E. coli, a species of fecal coliform bacteria specific to fecal material from humans and other warm-blooded animals, as the best indicator of health risk in freshwater. Perhaps surprisingly, fecal coliform as a group (Total Coliform) is considered a poor indicator of the risk of digestive system illness.

Bacterial contamination is highly variable. To smooth that variability, results are usually presented as the geometric mean of several readings. The table below shows the geometric mean for September and October at the two sites we sampled. It’s interesting to note that half of samples had Enterococci levels below the detection limit of 10 MPN/100 ml. However, because there are some Enterococci present and to avoid underestimating the level of contamination, values below the detection limit are set to the detection limit of 10 MPN for calculating the geometric mean. The Enterococcus limit for safe contact recreation for a single day is 104 MPN/100 ml and for the 30-day geometric mean, 35 MPN/100 ml—clearly above our measurements.

Geometric Mean for the Month

Dates                           Piper Park Dock          MRA Dock

September 2020             12 MPN/100 ml            16 MPN/100 ml

October 2020                12 MPN/100 ml            10 MPN/100 ml

Next year, we’ll begin testing in April and post the weekly results and the monthly geometric mean on our website. We recommend getting your drinking water from MMWD, but swimming in the creek is not likely to sicken you.

There is no indication that the relatively low level of bacterial contamination in Corte Madera Creek is harmful to wildlife.

We extend thanks to Mark Koekemoer, CMSA Laboratory Director, for training us to collect and handle samples, providing sample bottles, and helping to interpret results. He and his staff have been very helpful in our effort to use science to answer the question: Is it safe to swim in Corte Madera Creek?

The Problem with Paving the Planet

by Laura Lovett

If you’ve lived in the Ross Valley for many years, it may seem like Corte Madera Creek and its tributaries overflow more quickly these days, particularly during a heavy rain. This isn’t just your imagination.

A recent study by hydrologist and public policy advisor Annalise Blum and her colleagues used an extremely large data set covering 39 years of records from 280 stream gauges in the U.S., combined with a statistical model developed from economics, to untangle the relationship between impervious surfaces and their impact on nearby waterways. The result? For every 1 percent a town increased public impervious surfaces—roads, parking lots, sidewalks—the annual flood magnitude in nearby rivers and streams increased 3.3 percent.

We have gotten quite good at diverting and piping rainwater away from our homes but all that water has to go somewhere. In a natural landscape, a good portion would soak into the ground where it falls. This replenishes the water table, keeps our vegetation alive by feeding the plants and the microbial communities among their roots, and yields plants with a higher moisture content that don’t dry out and catch fire as quickly. A higher water table also feeds creeks in the summer, benefitting fish. Slowing the water down and keeping it on site has numerous benefits. Why are we so quick to label it a problem and shunt it off to the storm drain?

Blum’s study used data from towns and cities but it applies to homeowners as well. There is a great deal that individuals can do. Every square foot of impervious surface around our homes that we remove and replace with materials that allow rain to soak in helps the soil beneath us and reduces flood levels in nearby creeks. What we accomplish ourselves eliminates the need for more taxes and the wait for the county to act. Here are some options.

Cement  We are incredibly fond of laying concrete as an inexpensive solution to everything, but how many of these uses really have to be solid concrete? Can the path to your garage be stones or bricks laid in sand? How about using decomposed granite, very fine rock particles that are compacted to be quite stable but remain water absorbent? It comes in beautiful natural colors and resists weeds once compact. Convert the pad under your barbecue grill to slabs of stone (or even squares of concrete) with creeping thyme planted in between; then you can add a little thyme to the coals to flavor what you’re grilling! Many types of walkways and outdoor pads can easily be made more porous.

A path of blocks invites creativity and allows rain to soak in. Photo by Uzu Design

Curb Cuts  These are, as they sound, cuts in the curbs along streets and driveways that allow water running along curbs to be diverted into vegetated areas rather than into the storm drain. The area on your property adjacent to the cut needs to slope away from the roadway and will need a swale—a scooped depression in the earth that will catch and hold the water until it has a chance to soak in. These swales may have rocks on the edges for aesthetics and soil stabilization, and should be vegetated with moisture-loving plants that don’t mind having wet feet for a short while. The Mill Valley Library on Throckmorton has a bioswale full of native plants that catches and slows rain at the southeast end of their building.

Weed Cloth  Choose weed cloth with a very fine mesh rather than solid black plastic as the weed-blocking layer under gravel areas and trees. The soil needs air circulation as well as water to remain healthy.

An informal path of decomposed granite is an environmentally-friendly alternative to concrete. Photo by Matt Ross

Paving  Replacing asphalt with something pervious is a big undertaking. If you will be redoing your driveway or parking areas, however, consider using pervious paving. It looks just like regular asphalt but water can soak through it, preventing pooling and puddling and the resulting cracking. The Central Marin Police Station in Larkspur has permeable paving in the parking lots. You would never guess it isn’t standard asphalt; it looks much the same. Other options include using brick or stones set in sand on a gravel bed for some portion of the pavement, or simply considering just how much really needs to be paved and if some could be returned to lawn and garden beds.

Filter Strips  If Impervious pavement remains, vegetated filter strips of small rock and porous soil and plants can be placed along the edges of paving to increase the capture and filtration of water running off these surfaces. However, these should not be closer than 2 feet to the side of the house so water is not pooling next to foundation walls. If there is a full basement, allow 10 feet of separation between the two.

Compost  If water tends to run off your soil instead of sinking into it, add compost. Soil doesn’t absorb water unless it has carbon in it, it just sheds it. Carbon comes from organic matter—anything that is, or once was, living. Add any type of green compost: shredded leaves, grape seed mulch, mushroom compost, fireplace ashes, grass clippings, etc. The higher the soil’s carbon content, the more water it absorbs.

All of us have played a part in creating the conditions we currently face: a world with buildings and driveways and lots of concrete that prevent much of the winter precipitation from finding its way back into the water table. Corte Madera Creek empties into the Bay, which is now higher due to sea level rise, creating a “plug” at the mouth of the creek that prevents creek flow from draining out of the watershed during high tides. Under these conditions, all it can do is spread sideways. No one needs to wait for the county to engineer a solution, however. Every household can undertake one or more actions on this list and get us closer to our goal. Let’s help that water get back in the ground where it is beneficial and needed.

How High’s the Water, Ma?

by Sandy Guldman

        How high’s the water, Ma? Two feet high and risin’
                                                   Johnny Cash (1959)
This song resonates with residents of Corte Madera Creek watershed each winter when we witness king tides. The flooding is obvious, but over the long term, rising sea level has other damaging impacts. If marshes are converted to open water and mudflats, we lose their many environmental benefits, including habitat for wildlife and nurseries for young fish, carbon sequestration, flood water capacity, and attenuation of storm surges.

The big question is what to do about it. The ultimate solution is to reduce the quantity of greenhouse gas we add to the atmosphere, but a substantial amount of sea-level rise is now inevitable and we need to respond to that inexorable rise.

The least environmentally friendly responses are hard surfaces, like concrete walls. The best solution is to retreat and provide space for wetlands and floodplains to expand as sea level rises and storms become more intense. But we live in a developed area, and there is a limit to how much developed land we can abandon. The tradeoffs are difficult and we face a balancing act.

Marin County’s coordinated planning for sea level rise along the bay shoreline, BayWAVE, is a planning effort led by multiple agencies, partners, and municipalities, including the County. It is studying a number of approaches to solve the crisis. One project, designed to respond to climate change and sea-level rise, is the Lower COM Corte Madera Creek Habitat Restoration Project. Friends received a grant from the Coastal Conservancy and hired a team of experts to prepare 65% complete designs for partial removal of the concrete channel in Kentfield downstream of Stadium Way. The strategy in this area is to remove or lower the concrete walls and create a gently sloping bank.

Initially, most of the newly established vegetation on the bank will be transitional between tidal marsh and upland. Transition zone plants are salt tolerant and provide refugia for marsh wildlife during high tides. As sea-level slowly rises, the transition zone plants will be replaced by high marsh and then low marsh plants, preserving valuable tidal marsh and its many benefits.

An artist’s impression of proposed alterations to the downstream end of the concrete channel. Image by Scott Walls, walls land+water

Predictions of the amount of sea level rise by 2100 vary widely. This design uses estimates of sea level rise based on the San Francisco Bay Tidal Datums and Extreme Tides Study (2016) prepared for the Federal Emergency Management Agency and the San Francisco Bay Conservation and Development Commission.

It is estimated that by midcentury, the mean higher high water level in Corte Madera Creek will be 18 inches higher than at present. In 2100 this level may rise further by the same amount.

We expect that unless the rate of sea level rise can be slowed by significant reductions in greenhouse gas emissions, by 2100 other measures like walls and berms will be required to protect schools, homes, and businesses in the area.