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Earth

Sea Walls Might Just Make Floods Someone Else's Problem, Study Suggests (arstechnica.com) 77

Posted by BeauHD from the might-not-work-as-planned dept.
An anonymous reader writes: Protecting the coasts in the United States from the impacts of climate change comes with a hefty price tag. But new research shows that using sea walls to safeguard land can just make the rising tides a problem somewhere else. The paper, published in PNAS, looks into the effect of erecting sea walls in one location and what that means for other places along the coast. Using the San Francisco Bay as a case study, it also assesses the economic impacts of flood scenarios in the nonprotected regions. According to the paper, defending individual parcels of the shore can increase flooding elsewhere by as much as 36 million cubic meters. This can result in $723 million in damages for a single flooding event in the most dire situations -- costs can even exceed the damages that would have resulted otherwise in the protected region.

Robert Griffin, an assistant professor at the University of Massachusetts, Dartmouth's School of Marine Science and Technology, decided to look into what happens to unprotected areas. Griffin and his team combined hydrodynamic and economic modeling to investigate flood damages in the San Francisco Bay under a variety of different scenarios -- with different parts of the shore protected by walls with different lengths, for instance. (For the sake of the experiment, the sea walls were modeled as being infinitely high.) The team focused on problems brought on by tidal events, rather than storms, and broke the results down by amount of sea-level rise: 50 cm, 100 cm, 150 cm, and 200 cm above 2010 levels. The study "can be useful in a variety of outcomes through time," Griffin told Ars, adding that the 200 cm scenario is close to the high end of current projections for the year 2100. "Displacement effects relate to the morphology of the land. Places that are low-lying, and valleys, can potentially accommodate more water in a tidal flooding scenario. If you block those places in the case of a flood, those waters go elsewhere. If those other places aren't also similarly defended, then it can increase the damages on those places," Griffin said.

For example, if you protect the Napa-Sonoma shoreline, the Santa Clara Valley and San Leandro in the South Bay can expect to experience $82 million and $70 million in flooding damages, respectively, with a sea-level rise of 200 cm. San Rafael would also be hit with an additional $53 million in damages in the case of a flood. On the positive side of things, protecting parts of the South Bay could lead to small but widespread damage reductions. Protecting Alameda, for instance, could reduce flood damages in areas south of there, including San Lorenzo and Newark. It would also cut down damages on the opposite side of the shoreline, near Palo Alto and Silicon Valley, the paper notes. Though the modeling done in this research focuses on the San Francisco Bay, Griffin noted that other parts of the world's coasts could see similar effects. Further, around 468 million people live close to bays and estuaries, according to the paper. Considering sea walls are already in place along many coasts, these displaced damages could already be happening -- though potentially to a lesser extent than if the sea level reached the paper's more dire levels.
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Sea Walls Might Just Make Floods Someone Else's Problem, Study Suggests More

Sea Walls Might Just Make Floods Someone Else's Problem, Study Suggests

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  • And the dumbass news award for 2021 goes to...

    • Re:No shit (Score:5, Insightful)

      by Kernel Kurtz ( 182424 ) on Friday July 16, 2021 @10:40PM (#61590603)
      Yeah whoever would have thought artificially moving water around would have winners and losers?

      Sea walls, dams, canals, dikes - probably not often it is a win all around.

      • Re: No shit (Score:5, Insightful)

        by MrNaz ( 730548 ) on Saturday July 17, 2021 @12:12AM (#61590725) Homepage

        Making my $1 problem someone else's $2 problem becasue I'm rich.

        It's the American way.

        • Making my $1 problem someone else's $2 problem becasue I'm rich.

          It's the American way.

          Or making my $10 San Francisco problem a $1 problem along the largely-uninhabited Pacific coast a few miles away.

          Less snarky, cities have very dense and expensive waterfronts. If you move the water a few miles away, there are way fewer people and and buildings.

          It's still not a great permanent solution but it may be a cheap short-term mitigation strategy.

      • Re: (Score:2)

        by tragedy ( 27079 )

        Next thing they might figure out that it also might affect the flow of sand too and therefore beach formation, etc. Also that it might affect wildlife

      • Well, even obvious universal truths need to occasionally be tested and validated. In this case we all rest comfortably being certain that: A) Shit continues to roll down hill; and, B) Pascalâ(TM)s principle holds â" water seeks itâ(TM)s own level.

    • Re: (Score:2, Informative)

      by kot-begemot-uk ( 6104030 )
      To the dumbass who did not plan soak areas around SF.

      The "protected"/"soak" planning scheme has been in use in Holland for a few decades now. People in soak areas are encouraged (and some times "encouraged" [quotes needed]) to move. Protected areas are really protected areas.

      As the soak areas gradually empty of valuable estate the damage from floods is less and less. From catastrophic in 1953 to whatevvver in the last big one a few years back. Not sure how they are faring at the moment (to early to coun

      • That will never happen in the USA. The Dutch have their "polder model" of problem solving. But that's too close to socialism for our tastes.

        After the floods in New Orleans, hydrological (including Dutch) were asked for recommendations to improve flood control. They pointed out that the current seawall system was too flimsy and something akin to a wider dike system should be constructed. But that would mean the rich folks living on the riverfront would have to abandon their property to the dike construction

    • Shockingly no one seems to consider this. I've been seeing articles and videos for years on the idea of walling off the North Sea in order to protect the Northern Europe coastline. Not once does anyone consider the fact that the water has to go somewhere else.

  • ... if you played the right video games. For this particular lesson, I recommend "Cities: Skylines" published by Paradox. If you get your dams and seawalls wrong, suddenly everything becomes waterfront property. This seems like common sense but there's really nothing like actually seeing it happen from far above.

    • Would also add that I've been seeing these kinds of headlines since the 90s.

      • you must be young

        • Yeah, are you saying we've been seeing these stories since the 60s?

          • Re: (Score:2)

            by nagora ( 177841 )

            Yeah, are you saying we've been seeing these stories since the 60s?

            In the UK we have, since a range of coastal floods in the early 50s. It was quickly seen that, yes, water doesn't just vanish when you keep it out of your farmland/cities.

            It's worth continuing to investigate and model, but it's not really news.

      • Would also add that I've been seeing these kinds of headlines since the 90s.

        Sea walls, even breakwaters, have long been known to affect the local environment away from the structure. The old adage is Along the ocean, fixing your problem often just makes a problem for someone else.

  • Won't somebody PLEASE think of the wealthy! (Score:5, Insightful)

    by azcoyote ( 1101073 ) on Friday July 16, 2021 @10:42PM (#61590605)
    We need sea walls and other billion-dollar disaster-mitigation efforts so we can save the pricey oceanside retreats that rich people keep on hand as their second or hitrd vacation home! Heaven forbid that a wealthy person should have to think practically and weigh future costs as though the government isn't going to just step in and take care of them when their beach house washes away... /sarcasm

    • I don't think the rich will want to stay at a property when the only view they get is a wall.

      This may convince the rich to move to other places where they have something to view, instead of just a wall.

    • East coast beach nourishment projects have been going on for decades. Because well, barrier islands shift, but if you have houses on them as the wealthy do, they need the island to stay where it is. Much like hurricane damage where people just rebuild the same house over again, and literally rinse and repeat a few years later.
    • Wow clever on a couple levels there. Good job. But i wonder the reality of this. After Katrina we rebuilt the New Orleans Levys and we still are unsure it will handle another tropical cyclone like Katrina. How is a levy worse than this proposed non-existing holy grail of ocean barriers?

  • The valid reason is cold hard economics, applicable to seaports and related structures supporting maritime business.

    The bullshit reason is esthetic childish nonsense.

    Choose wisely or not, but wise choices make it not your problem in the first place and you can always drive to play in the ocean whilst living inland. Those who cherish silly shit (like buying condos in Florida because they crave beachfront property) get what they signed up for. Every aspect of life should be planned and reviewed like a militar

    • I very intentionally bought my Maui condo 70 feet above sea level. And I am on the third story. And in a low danger tsunami zone. And in a modern concrete and still building.

      A low tsunami might be nice, freeing up my view.

      • Megatsunami time: Makawao stands a chance.

    • Unfortunately in this country we have this really stupid federal flood relief fund that lets you rebuild in the same place.

      I'm not against the relief, I'm against being allowed to spend it on rebuilding on the same location.

  • I knew they were up to something with their levees and gates.
  • they've known that happens basically always, it's why they let some places just erode into the ocean. Here's the fun thought, how many of those who get taxed to build the sea wall that floods them into homelessness are gonna drive out to such a sea wall with a bomb.

  • So they're saying to not build sea walls? Did they note that the SF Bay is not blocked from the ocean? You put water in the bay it will flow towards the ocean. If the bay rises by a foot that means the Pacific Ocean rises by a foot.

    Maybe these people should think about blocking all rivers that feed all oceans and sequester all that water. Maybe they should build big snow makers in Glacier Bay and sequester all that extra water into the glaciers. Then do the same in the Antarctic. ;)

  • Maybe, maybe not. Then again, a giant lock under the Golden Gate Bridge wouldn't be too hard to make and could handle the flow of many marine vessels at a time? I am wondering where the Sacamento River would flow then? Eventually the Central Valley of California would fill up and turn into a somewhat fresh water sea, maybe? So many possibilities. Not one of them looking all that great though.

    • I am wondering where the Sacamento River would flow then?

      It used to flow out through Monterey. It would require a bit of erosion for that to happen again, though.

    • Re: (Score:2)

      by Sique ( 173459 )
      That's why levy structures like in the Netherlands only work in regions with strong tides. During high tide, you close the flood gates, so seawater remains outside. During low tide, you open them and let the rivers flow into the sea. If you don't have enough height difference between the sea and the rivers, all your dam does is impounding the flow of the rivers, and creating artificial lakes.

      For the record, the difference between high tide and low tide along the Dutch coast is somewhere between five and s

  • I know this is a radical idea, but...how about just moving uphill, away from the shoreline? Rising sea levels are nothing new - this has been going on for centuries. So it's no surprise that land built on a hundred years ago may slowly be untenable. Give in to reality, instead of fighting it.

    • Re: (Score:3)

      by tragedy ( 27079 )

      It's a calculation. Can you mitigate the problem for less than the cost of replacing all the buildings and infrastructure that will be inundated? If the answer is yes, then it's probably worth doing it. Obviously the cost has to also account for environmental costs, etc.

    • Because there's capital locked into all that infrastructure, buildings and things we built in now-unsuitable areas. It's not like you can magically transplant entire neighborhood and cities elsewhere. Basically, people's lives and business would have to start over.

      That's when they can afford it. When they can't, they either flee (ultra poor people who wear their belongings on their backs, called "climate refugees"), or they stay put and hope it won't happen again (also called "New Orleanians")

      • Re: (Score:2)

        by SeaFox ( 739806 )

        Because there's capital locked into all that infrastructure, buildings and things we built in now-unsuitable areas. It's not like you can magically transplant entire neighborhood and cities elsewhere. Basically, people's lives and business would have to start over.

        How is that any different than when someone decides to build a dam on a river and a town ends up getting sunk into a valley now completely underwater. The Army Corps of Engineers or whoever decided to build it didn't give a damn (pun intended) about their infrastructure or established homes.

        • How is that any different than when someone decides to build a dam on a river and a town ends up getting sunk into a valley now completely underwater. The Army Corps of Engineers or whoever decided to build it didn't give a damn (pun intended) about their infrastructure or established homes.

          Those were poor people. We're talking about rich people of the kinds that own seafront property here.

    • If you look at the costs, in Santa Clara county the cost is $82 million in the most extreme case. It sounds like a big number, but it's actually just a few houses (or warehouses or shops, along that coast).

      Because of the high cost of property in the area, even small amounts of damage will have big numbers.

    • how about just moving uphill

      Where to? You realise the cost of relocating such a significant portion of the population in coastal cities dwarfs the cost of dealing with flooding right? We're not talking about one rich cunt who doesn't want to give up a sea view home.

      Heck I live in a 2nd story apartment 60km from the coast and I'm still 1m below sea level. We're actually pretty good at fighting reality. We just need to actually do it.

    • Re: (Score:2)

      by AmiMoJo ( 196126 )

      In the past changes were slow and only a few people needed to move at a time. Now changes are fast and the upheaval will cause severe problems for many individuals and businesses.

      "Just move" also assumes that people can somehow afford to do that. Take a city like Portsmouth in the UK as an example, much of it is below sea level and much of it is at the lower end of the economic scale. If it became uninhabitable then a lot of people would lose their homes and not be able to afford new ones.

      https://youtu.be/0 [youtu.be]

  • "Griffin told Ars, adding that the 200 cm scenario (Score:4, Interesting)

    by ishmaelflood ( 643277 ) on Saturday July 17, 2021 @02:46AM (#61590877)

    "Griffin told Ars, adding that the 200 cm scenario is close to the high end of current projections for the year 2100"

    80 years from now at 3mm/year= 24 cm

    3mm/year figure from, "one third of 24cm in last 25 years" from here

    https://www.climate.gov/news-f... [climate.gov].

    If you look at the californian coast on the map you'll see since 1993 there is very little change in sea level. Bit inconvenient.

    No I didn't RTFA. I ROTFS (relied on the fucking summary).

    • 80 years from now at 3mm/year= 24 cm
      The yearly sea level rise will increase. Pretty rapidly in 20 or 30 years.

      "Griffin told Ars, adding that the 200 cm scenario is close to the high end of current projections for the year 2100"
      This is about a high tide. Especially under the "moon conditions" mentioned in the article.

      Basically: has nothing to do with your idiotic "oh, but the sea level is only rising 3mm per year".

  • Instead of building sea walls in select locations on the SF Bay coasts, dam off the whole bay. Replace the Golden Gate bridge with a dam (and a set of locks), build a new seaport on the outside of the dam.
    This protects the entire bay, solves the bridge capacity problem and makes land reclamation on the edges of San Francisco easier so it solves the shortage of land problem.

  • A much greater problem is the building of dykes and levee's along rivers that force more and more water downstream. This causes the dykes and levee's further downstream to be built higher and higher, eventually the water will overtop or breach the dykes and levee's. See Red River and Missouri River spring floods. A cure would be for new dykes or levee's to be built and ones already in service to be reduced in hight to a no greater than somewhere between a 100 or 500 year flood stage. Yes, there will be floo

  • This does not apply to the coastline in general. It applies to bays like SF bay, where the water gets pushed through the Golden Gate and then has nowhere to go.

    • Re: (Score:2)

      by jythie ( 914043 )
      ding ding ding.

      You just hit on why this paper is not the 'obvious garbage' many of commenters have been saying it is. The general effect is well known, it was probably taught to the researcher in grad school. But how it plays out in specific regions with specific configurations is still something you can try to work out on a case by case basis. In this instance they took a particular region and tried to simulation how this known effect would interact with its particular geography. Good research (I am

  • How does this work? The sea is huge, I cheked. (Score:3)

    by MacMann ( 7518492 ) on Saturday July 17, 2021 @07:47AM (#61591243)

    I know these people are supposed to be really smart and get paid a lot of money for sharing this with other people but this does not make sense. The sea is huge and any walls we build to hold it back isn't going to do anything noticeable to the total sea levels. As an example consider the tsunami that moved Japan three feet to the left a few years ago. That was a huge wave that made the local sea levels about 15 meters higher. Holding that back from flooding one part of the coast isn't going to make any noticeable difference further up or down a coast. That is unless I'm missing something. Maybe this works out but that only means that these highly paid smart people suck at explaining things.

    • From TFA:

      "Recent modeling studies of shoreline adaptation and SLR in San Francisco Bay have demonstrated that shoreline protection using engineered structures like seawalls can cause amplification of the tides by reducing frictional damping in shallow areas along the perimeter of the bay and enhancing reflection of the incoming tidal wave at the shoreline (26, 28, 29). These changes in tidal amplitude can influence the magnitude and spatial distribution of peak water levels and inundation around the bay."

      So

    • The study is about bays and estuaries, not the general coastline. The Ars Technica article glosses over this, but it's clearly mentioned in the study's abstract.

  • There are a lot of posts here along the lines of "haha stupid researchers 'discovering' something obvious!", but that's because the summary is a disservice to the actual paper. It's not about whether the phenomenon would happen - of course it would - it's about modeling and quantifying its effects.

    Of course a wall diverts water flow, but where does it go, how does it flow, how far inland does it travel, how does local geography and topography impact the flow (like being in SF bay), and how to all of those f

  • I guess what may become another American past time will be going to abandoned coastal cities to watch tall buildings crumbling into the sea. A bit like visiting the Grand Canyon & watching geysers at Yellowstone Park. I wonder what an abandoned, rotting city smells like though?

    Many large cities are built around estuaries, e.g. NY, London & Shanghai, so sea walls would be a bit more complicated than simply keeping sea water out. London already has the Thames Barrier (10 years to build at a cost of 1/

    • What if we were to take the opportunity to build better designed, more efficient cities on higher ground? Ones with beautiful public spaces*, integrated planning (i.e. facilities & amenities distributed & within short walking distances), efficient transport (i.e. integrated public mass-transit systems & minimal use of private cars), & energy efficient buildings to reduce living costs & environmental impact. How does that sound? Not a radical redesigns like previous 'city of the future' p

      • Americans are stubborn and want to find things out for themselves, like in Florida where they keep building houses and condos on higher and higher stilts. At this rate I expect them to dredge the roadways and rename south Florida “New Venice” around 2120.
  • New Orleans was in danger of flooding so they broke levees up river to divert flood waters costing those people everything instead of themselves.
    Article one [smithsonianmag.com]
    Article two [pbs.org]

  • will Mexico pay for them?

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