The City of Alameda had just endorsed concept designs to address sea level rise for its north shore, when recent storms shifted attention to the south shore.
The erosion of sand from our shoreline yet again raises an important question that the City is not considering in its adaptation planning: Should maintaining the beach be the primary objective in dealing with sea level rise and increasingly powerful storms?
On the shelf sits a 1981 environmental assessment by the U.S. Army Corps of Engineers (Corps) that could help answer the question.
The Corps studied 17 possibilities for staving off the erosion that would eventually undermine Shoreline Drive. They evaluated a variety of structural solutions, including beach fill, groins, breakwaters, seawalls, sills, marsh extensions, and combinations thereof.
Three alternatives were deemed economically and environmentally sound: A rocky embankment called a revetment; a recreational sand beach; and a hybrid approach consisting of seawalls made with bags of cement, rocky embankments, and beach sand.
In the Corps’ 1981 assessment, the “Quarry Stone Revetment” alternative, essentially a rocky embankment, was rated as the “Environmental Quality Plan” because it would lead to expansion and enhancement of wildlife habitat, while providing long-term protection of Shoreline Drive.
But at the time, the City and the East Bay Regional Park District (EBRPD), which had jointly asked the Corps to conduct the assessment, decided to set beach recreation as the highest priority and chose the “Beach Fill with Medium Sand” alternative. They told the Corps that they and the state, not the Corps, would fund and perform the work, according to the assessment.
By choosing the “sand” alternative, 11 acres of mudflat was covered with sand. In order to sign off on the permit, the U.S. Fish and Wildlife Service required EBRPD to add 11 acres to their marsh and mudflat restoration project at Hayward Regional Shoreline as mitigation for the loss in Alameda, according to the assessment.
Ever since, EBRPD deploys a fleet of earthmoving equipment to shuttle wave-eroded sand from the ends of the beach back to where it came from, and haul in replacement sand by barge periodically. This year the agency also had to import truckloads of boulders to stabilize the shoreline and the lagoon pump apparatus located at the corner of Shoreline and Westline Drives.
The 1981 environmental assessment calculated that the sand beach, which had been constructed decades earlier, was receding at a rate of three to seven feet per year. “Greatest erosion is occurring on the point of land where Westline Drive joins Shoreline Drive,” states the report.
More than 40 years later, the beach erosion problem remains. “Coastal erosion of the sand dunes is already threatening a portion of the Bay Trail and Shoreline Drive,” states the draft mid-cycle update to the City’s Climate Action and Resiliency Plan (CARP) slated for approval on March 18. “As sea levels rise and storms increase in intensity, coastal erosion could become more widespread, increasing the extent of inland flooding.”
Yet, the CARP contemplates the same questions posed and answered by the Corps in 1981, and suggests going through the same exercise all over again, including repeating pilot studies of sand movement, but with the apparent primary objective of maintaining the beach.
“Understanding the natural movement of sand between the Bay and the beaches, and along the beach towards the San Leandro Bay Estuary will help inform potential natural-based pilot studies that may improve sand management and help address future sea level rise and coastal erosion,” states the CARP. “A more permanent solution is needed to mitigate coastal erosion and inland flooding, while also maintaining the beaches.”
Meanwhile, the state’s San Francisco Bay Conservation and Development Commission Regional Shoreline Adaptation Plan says to “Emphasize habitat restoration and nature-based solutions.” The regional adaptation plan is guided by the California Climate Adaptation Strategy, which advises, “Prioritize the use of natural infrastructure in efforts to protect and restore watersheds, coasts, marine waters, and ecosystems.”
The 1981 environmental assessment was so comprehensive, it even took into consideration pilot studies of the erosional movement of sand conducted prior to 1981. It also evaluated fish and wildlife impacts and stated that for the Beach Fill alternative, “Fish and shorebird feeding habitat would be reduced.” For the Quarry Stone Revetment alternative it stated, “Fish and shorebird feeding habitat would be increased.”
In describing the Quarry Stone Revetment alternative, the 1981 assessment stated that all of the remaining sand from decades earlier between Park Street and Westline Drive would eventually wash away and revert to mudflats and marsh like at Elsie Roemer Bird Sanctuary. “Marsh vegetation, wildlife, shellfish, and juvenile fish habitat, and shorebird feeding area would be enhanced and increased in total area,” stated the Environmental Assessment. “The rock revetment would replace sandy upper tidal flats with hard, rocky inter-tidal substrate, allowing shellfish attachment.”
The environmental assessment also noted that as the sand on the beach washed away, it would revert to a natural bottom type more conducive to small marine creatures, known as benthic organisms, and to shorebird feeding.
Whether revisiting the 1981 environmental assessment will change the recreational-heavy focus of the City’s long-term shoreline adaptation plans in the CARP is yet to be seen. But exploring the already provided alternatives could potentially point to the best nature-based solution.
Contributing writer Richard Bangert posts stories and photos about environmental issues on his blog Alameda Point Environmental Report. His writing is collected at AlamedaPost.com/Richard-Bangert.
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