Be very careful where you build the waterfront

Think again in addition to being a child on the beach, it builds walls around your sand castles. If these forts were properly designed, the tide would come in and wander around your kingdom before the walls finally eroded. By redirecting the water that increases the climb, you would save your castle, at least for a while.

Now think bigger. Imagine that you are an urban planner in an area threatened by the rising sea and that you have spent money to build the right waterfront. Entering the tide and holding on to the wall saves you billions of dollars in property damage. But: whomp whomp. Like the waves you once redirected around the sand castle, the rising waters hit the wall and flow into individual communities on your side. You have saved your neighbors, but you have put others at risk.

A new modeling shows how catastrophic this waterway phenomenon can be in San Francisco Bay, where sea levels can rise 7 meters in the next 80 years. “These rising waters have put millions of people and billions of dollars at risk in buildings,” says Anne Guerry, an official strategist and scientist at Stanford University’s Natural Capital Project. paper describing the research. It was published in the magazine this week Proceedings of the National Academy of Sciences. “One of the novelties of this work is that people don’t necessarily think about how communities, like the Bay Area, connect to each other through these shared waters,” he continues.

Guerry and his colleagues did the modeling by dividing it into coastal sections based on features such as geology. They then used hydrological models to show where the rise of the water would go if a certain part of the coast was fortified by sea walls. Basically, they imagined what would happen if the inhabitants of an area decided to protect themselves, without considering hydrology completely. “That water has to flow somewhere“And what we’ve found is that it ends up flowing into other communities, making the floods much worse.”

They also incorporated economic models to calculate how much damage this would do. For example, they estimate that if the local government demolished a wall near San Jose, in the city of South Bay, it would flood other communities with the equivalent of 14,400 Olympic-sized swimming pools. San Jose would be saved, but Redwood City and other nearby communities would be screwed. “This has the cost of additional flood damage of $ 723 million after the high tide only passed in the spring, when the waters are naturally highest,” says Guerry. “And that’s building a big boardwalk in a small part of the bay.” And that $ 700 million doesn’t count the damage it could do to ecosystems and fisheries, so the count is conservative.

Additional water thrown back by the walls of San Jose would accumulate across the bay, Napa and Sonoman, 50 miles north. The damage would go the other way: if the Napa and Sonoma coasts were walled, South Bay would receive $ 10 million in compensation.

That’s not great news, considering that humans have a habit of building big cities on the coast, which urban planners have to do now. fortified, and sea walls are often the best defense available. The authors of this article point out that by 2100, the U.S. is projected to spend $ 300 billion on the coast to sustain rising sea levels and higher storm surges. stronger through climate change. Lawmakers will soon have to consider whether to spend it $ 26 billion to surround Houston. Jakarta also needs to build a huge wall, until the earth beneath it can’t do it alone it ceases to sink.

So far, politicians have done it suppose maritime suitcases can have a negative impact on surrounding communities, but this new research puts numbers on potential harm, says Laura Feinstein, director of sustainability and resilience policy at SPUR, a nonprofit public policy group in the Bay Area. (He was not involved in the research.) “It’s a really quantitative and rigorous demonstration of what people have always said about sea level rise, which is that regions sink or swim together,” he says. “If an area spills resources to shield its coastline, that will exacerbate residents’ sea level rise.”