Completed in 1892, the Searsville Dam sits astride San Francisquito Creek, which connects watershed in the mountains above Silicon Valley to the San Francisco Bay. Sedimentation has “reduced the reservoir to 10 percent of its original capacity“. At this rate, the reservoir will completely fill in 15 years, and then, sediment would wash over the dam, through the creek, and into the bay. This old dam and silted-up reservoir pose both a threat and an opportunity for the Bay Area: sediment washing down the creek returns an age-old flood threat to downstream communities like Palo Alto and Menlo Park; one reservoir of sediment is a potential source of mud needed to help save the South Bay from sea-level rise.
Sediment washing over a completely filled dam could clog the creek and lead to flooding. Floods aren’t new to the alluvial Santa Clara Valley. Resting on up to 1,500 feet of sediment, the valley floor is broad and flat because of past floods deposited sediment across the valley. The Bay Area was thinly settled when the dam was built in 1892. Since then, Silicon Valley homes and offices have been built next to the creek, limiting flood control options.
In addition to flood risk from the creek, the Bay Area has a long shoreline that is at risk from rising seas. “Back in June 2016, Bay Area voters approved Measure AA to raise $500 million to pay for wetlands restoration, flood control and wildlife projects around San Francisco Bay.” But to protect the Bay Area, the structures will need more mud than is available, per the Scientific American post.
Searsville Dam holds “approximately 2.7 million cubic yards of sediment that has built up behind the dam since its construction in 1892“. This sediment is a potential source of mud for the Bay.
Finally, Searsville Dam filling with sediment illustrates that a dam has a limited lifetime. The Bay Area is planning to build another dam. As we do this, we should consider the life-cycle costs of new dams as well as existing dams.
Continue reading Stanford’s Searsville Dam
Northern California and my home town of Los Altos received more rain than normal in January and February 2017, as the atmospheric river continued to flow here. After five years of drought, California’s surface water and snow pack are above normal.
In early March, bee’s bliss sage (salvia ‘Bee’s Bliss’) begins to bloom, attracting bees. Bee’s bliss sage is a California native plant that is drought tolerant and likes full sun.
Continue reading Los Altos Weather – Soggy February
This week we took a road trip to the Golden Gate Bridge in San Francisco. The Golden Gate is the gap in the mountains were the San Francisco Bay meets the Pacific Ocean. The Bridge spans the gap between San Francisco and Marin County. With clear skies and a high of 61 degrees F, it was a beautiful day for bicycling and hiking.
Continue reading Golden Gate Bridge in November
Despite the promise of high rainfall due to El Niño, March rainfall in my home town of Los Altos, California was about normal. March marks the end of our wet season. Our dry season starts now, with our average monthly rainfall being less than an inch per month through October. Barring unusually rainy weather during our dry season, our drought will continue for months.
Plans to counter sea-level rise by building levees around San Francisco Bay may be hampered by a lack of mud, according to the Scientific American.
The featured image is blue-eyed grass, sisyrinchium bellum, which is blooming now. A California native plant, it’s a bunching grass with small, purple to blue flowers.
Continue reading Los Altos Weather: Fairly Wet March
In early January we drove to California’s delta to see sandhill cranes wintering there. Sandhill cranes are tall (.8 – 1.2 m or 2.5 ft – 4 ft) with large wingspans (1.6 – 2.3 m or 5.5 ft – 7.5 ft). Sandhill cranes soar well and migrate long distances. With their long legs, neck and wings, they need time and space to take off, so they land in open fields. Sandhill cranes stay in groups for safety in numbers, with one or more cranes on the lookout while others root for seeds or anything else they can find.
Continue reading Sandhill Cranes in the Delta
Last week we dined in San Francisco during SF Restaurant Week, when restaurants offer discounted, fixed-price meals. We rode the train to the City and walked along the Embarcadero, taking in views of the bay. San Francisco is getting ready for the Super Bowl and Chinese New Year.
Shown above, the San Francisco Embarcadero is named for the many piers used to embark on voyages when San Francisco was a port. The wooden piers require fire boats in case of fire. Most of the piers are gone, and the fire boat is still needed. Today the Embarcadero is a great promenade. The San Francisco-Oakland Bay Bridge stretches toward Yerba Buena Island.
Continue reading A Day in San Francisco
Last Thursday I went on a hike at El Corte de Madera Creek Open Space Preserve (OSP), sponsored by the San Francisco Chronicle newspaper. The preserve is named for the creek; the name means place to cut wood in Spanish. There were a lot of trees when the Spanish first settled here, but the area was clear cut in the late 19th century. We saw an 1800-year-old redwood tree, an interesting rock formation, the Pacific Ocean, and California native plants.
Continue reading El Corte de Madera Creek OSP