In my last blog post, I covered how sea level rise will affect your community. Today’s post is about what we can do to address this problem.
The first and most obvious answer is that we must take more serious action to reduce the greenhouse gasses that cause sea level rise and other climate change impacts. However, the simple fact is that the ocean is already rising and will continue to do so for at least a few decades, no matter what because the heat is already in the ocean. Therefore, we must begin thinking about how our communities can adapt to the rising sea level that we know is coming.
Keeping the water out
As I mentioned last time, preventing low-lying Bayfront infrastructure from flooding is critical for all of us, no matter where we live. The old-fashioned way to create physical barriers against inundation from the Bay was to build hard levees of earth or concrete. You can see many such levees along the Bayfront, and more will be constructed in the future. But studies have now shown that in locations where this is feasible, it’s more effective to create “horizontal levees” – long, gradual slopes that mimic natural marshlands and tidal flats. These horizontal levees are much better at absorbing wave action energy, both because of their gradual slopes and their marshland vegetation that soaks up water like a sponge. They also provide essential habitat for wetland species at risk of extinction. In Palo Alto, a horizontal levee project is planned to protect the Baylands and the wastewater treatment plant while also creating a transition zone from tidal marshlands to dry upland habitat.
Historically, San Francisco Bay was ringed with tidal wetlands that provided a natural buffer against storms and rising seas. Some of these wetlands were not permanently destroyed but were merely diked off for salt production, which means they can be restored. The South Bay Shoreline Project, led by the U.S. Army Corps of Engineers, aims to combine wetland restoration and levee construction to protect Alviso and the San Jose/Santa Clara wastewater treatment plant, with future phases located on the Sunnyvale, Mountain View and Palo Alto shorelines.
Adapting to sea level rise
If we’re going to continue to allow new development in areas that are vulnerable to sea level rise, we need to require that development to adapt to the changing climate. This means establishing buffer zones from the shoreline and creeks that can overtop their banks. It means requiring new developments to be elevated above the level where flooding is likely to occur. It means requiring developers to contribute to funding shoreline protections and stormwater infrastructure necessary to protect that new development.
Ultimately, we must relocate our communities and critical infrastructure away from flood-prone areas, including roads, wastewater treatment plants, and emergency services. “Managed retreat,” as this is called, is a controversial topic, but when faced with the reality of rising seas, the simple fact is that we can have either managed retreat or unmanaged retreat. When our communities are below sea level, the result can be constant flooding from backed-up storm drains and shallow groundwater rises. Sooner or later, neighborhoods will simply become unlivable due to the frequency of such flooding.
Coastal bluff erosion
On the San Mateo County coast, problems from sea level rise extend beyond flooding of low-lying areas. The oceanside cliffs and bluffs that make our coast so scenic also create an entirely different type of climate hazard when increased wave action during storms results in erosion and the sudden collapse of big chunks of the coastal bluffs. Efforts to protect the bluffs with revetments or rip-rap (layers of large boulders) make erosion worse by reflecting wave action back towards the ocean or onto adjacent unprotected bluffs. This also results in the loss of beaches, as the increased wave action washes away the beach sand.
Investing in our future
Protecting our communities against sea level rise will require investment. A report by several local agencies issued in July of this year found that protecting all the vulnerable areas on the shoreline by 2050 is estimated to cost $110 billion. But the same report estimated the cost of not taking action at $230 billion – more than twice as much. The conclusion is obvious: only by facing the reality of climate change and accepting that we need to invest in protecting our communities can we hope to create a sustainable future for our region.