In the late 1940s, there was a rush to fill-in parts of San Francisco Bay for development. A grand proposal, the Reber Plan — based on erecting a system of barriers — took the limelight. When the U.S. Army Corps of Engineers ran a feasibility study, the project was discarded. But filling of the Bay continued and, by the time I was in junior high school in the late 1960s, almost a third of the Bay had been lost.

At that time, Save The Bay was founded by three residents of Berkeley to fight this trend. Their work led to the California legislature passing the McAteer-Petris Act, which created the Bay Conservation and Development Commission (BCDC) to regulate bay fill, restore wetlands and enhance public access to the shoreline.

Fast forward to today, my hair is going grey, and I am a BCDC Commissioner facing a different problem than my predecessors. Instead of a Bay shrinking as it is filled in, we have a Bay that is getting bigger as sea level rises. Along the shorelines is a complex tapestry of ports and parks, refineries and residences, office buildings, airports, pipelines, roads and more. All of these assets will be threatened as sea level rises, slowly right now but escalating in speed through this century. We will have to do something about it.

An army of individuals, groups and governmental agencies are considering how best to prepare for our changing future. This will be a huge undertaking. The shoreline of San Francisco Bay would stretch about one-half the length of the entire California coast.

There’s so much variation along these shores that any "one size fits all" solution will be woefully inadequate. Some places (such as San Francisco’s Financial District) can only be protected by walls, while in other places, the most effective strategies are those tuned to the ecosystems already present. These might include flood protection through restoration of wetlands, construction of rocky beaches (that absorb wave energy) and other strategies. This means working within what the San Francisco Estuary Institute has termed "nature’s jurisdictions," requiring cities or counties to take collaborative action across ecosystems rather than just acting within their political boundaries.

In an enclosed estuary like San Francisco Bay, changing the shore in one location can impact the flooding in another. Sea walls built in one part of an estuary could actually cause worse flooding and economic damage in nearby unprotected communities. The results of a recent study showed that building a sea wall in San Jose will raise the water level of the Bay 60 miles away in Napa.

Given the complexities, it may seem better to just wall off the ocean to keep higher water away from the Bay shore. In some places, like the Thames River in England, such systems have provided flood protection from storm surges. A study for Boston Harbor recently rejected a proposed ocean barrier as costing more than the benefits it would provide. While a barrier can help protect from the temporary high water due to a storm, accelerating sea level rise presents a sustained challenge that requires creative and targeted solutions.

Recently, the mayor of San Jose suggested that a barrier could be built across the Golden Gate to protect the Bay shoreline from future flooding. My colleague Jeremy Lowe and I describe in the San Francisco Chronicle why this a short-sighted and counter productive approach to our problem. The shoreline of the Bay requires a diverse, flexible and dynamic set of solutions that accepts the rising water instead of denying it. Our new climate has already arrived, and more changes are on the way. We’ve got to get to work.

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