5 ms·

There is one thing I don't understand about the article. The rise in groundwater level should follow the average increase in sea level. It is not like a big wav

by phicoh 5y ago

There is one thing I don't understand about the article. The rise in groundwater level should follow the average increase in sea level. It is not like a big wave would suddenly affect the groundwater level. Assuming houses last for 50 years and during the next 50 years the sealevel can increase by around 50cm, it should be easy to check if buildings near the coast are high enough that they can accept this change in sealevel. Of course, damage done by flooding does depend on how big waves are. So you need levees and seawalls long before you get a groundwater problem. That said, you don't want to pump fresh water out of the ground close to the sea (unless you inject at least as much fresh water). But that is independent of sealevel rising. Finally, plenty of Dutch houses are built in swamps below sealevel. The technology exists.

iskander 5y ago
I haven't read the article yet but one thing that makes more complicated in the US is the widespread use of septic tanks. The leach field will flood before the actual surface.
- q1w2 5y ago
  Most septic tanks are not in coastal properties. The water table isn't going to change for a property unless you're right on the water or living on wide low lying march/delta type areas.
  - iskander 5y ago
    In Florida and much of the Gulf Coast though... Check out this map of population density: https://vividmaps.com/wp-content/uploads/2021/10/metropolitan-areas-population-density.gif https://vividmaps.com/wp-content/uploads/2021/10/metropolita... All those dense spots in Florida and along the Gulf are also more likely than most US urban areas to use septic tanks. That's a lot of brackish poop, clogged toilets, and environmental contamination coming in the next few decades.
    - q1w2 5y ago
      Given the high water table in Florida, only people living in the countryside have septic tanks. None on the coast would have a septic tank
      - iskander 5y ago
        Hahaha, spoken like someone who hasn't lived in Florida. Miami-Dade is full of septic tank. I think the state has about ~3M of them total. No one thought about the coastal water table when installing them, and I honestly don't know if they do even now. See: https://www.gainesville.com/story/sports/columns/dooley/2019/06/01/florida-septic-tanks-in-crisis/5009400007/ https://www.gainesville.com/story/sports/columns/dooley/2019... Situation is similar across the whole Gulf Coast. You really shouldn't assume any of this was rationally planned.
wongarsu 5y ago
Sea level rise in itself is a complicated subject. Some regions of the ocean see easily twice the global average of sea level rise, while other regions barely change (currents and winds have a large effect on sea level). On the coast this gets further complicated because the ground itself is also moving up or down (mostly due to settling, or century-long rebound from the loss of glaciers) [1]. I would assume ground water adds another layer of complexity since it also depends on local geography 1: https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level https://www.climate.gov/news-features/understanding-climate/...
DoingIsLearning 5y ago
> Of course, damage done by flooding does depend on how big waves are. So you need levees and seawalls long before you get a groundwater problem. Actually Germany and Netherlands experienced massive floods this year with increased river volumes in the Maas due to excess rain and ice melt in the Alps. At least 200 people died, 10s of thousands relocated. My point is not all your flood threats are downstream from you. > Finally, plenty of Dutch houses are built in swamps below sealevel. The technology exists. The dutch have centuries of know how and an entirely separate body to oversee all water management the Rijkswaterstaat. To assume that their model can be easily copied is a massive underestimation of the problem/solutions.
- phicoh 5y ago
  There is an interesting thing related to the recent floods that happened in Begium, Germany and The Netherlands. The Netherlands spends quite a bit of effort estimating flood risks, and for more important water defenses tries to get the chance of disaster down to about one in 10000 years. However, it seems that this calculation is only done for the lower parts of the country. The Meuse was only taken seriously after a couple of floods in the 1990s (and works were just far enough in The Netherlands that places along the Meuse were mostly fine). However, for smaller rivers, nobody seems to care.

by phicoh 5y ago

iskander 5y ago

I haven't read the article yet but one thing that makes more complicated in the US is the widespread use of septic tanks. The leach field will flood before the actual surface.

q1w2 5y ago
Most septic tanks are not in coastal properties. The water table isn't going to change for a property unless you're right on the water or living on wide low lying march/delta type areas.
- iskander 5y ago
  In Florida and much of the Gulf Coast though... Check out this map of population density: https://vividmaps.com/wp-content/uploads/2021/10/metropolitan-areas-population-density.gif https://vividmaps.com/wp-content/uploads/2021/10/metropolita... All those dense spots in Florida and along the Gulf are also more likely than most US urban areas to use septic tanks. That's a lot of brackish poop, clogged toilets, and environmental contamination coming in the next few decades.
  - q1w2 5y ago
    Given the high water table in Florida, only people living in the countryside have septic tanks. None on the coast would have a septic tank
    - iskander 5y ago
      Hahaha, spoken like someone who hasn't lived in Florida. Miami-Dade is full of septic tank. I think the state has about ~3M of them total. No one thought about the coastal water table when installing them, and I honestly don't know if they do even now. See: https://www.gainesville.com/story/sports/columns/dooley/2019/06/01/florida-septic-tanks-in-crisis/5009400007/ https://www.gainesville.com/story/sports/columns/dooley/2019... Situation is similar across the whole Gulf Coast. You really shouldn't assume any of this was rationally planned.

wongarsu 5y ago

Sea level rise in itself is a complicated subject. Some regions of the ocean see easily twice the global average of sea level rise, while other regions barely change (currents and winds have a large effect on sea level). On the coast this gets further complicated because the ground itself is also moving up or down (mostly due to settling, or century-long rebound from the loss of glaciers) [1]. I would assume ground water adds another layer of complexity since it also depends on local geography 1: https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level https://www.climate.gov/news-features/understanding-climate/...

DoingIsLearning 5y ago

> Of course, damage done by flooding does depend on how big waves are. So you need levees and seawalls long before you get a groundwater problem. Actually Germany and Netherlands experienced massive floods this year with increased river volumes in the Maas due to excess rain and ice melt in the Alps. At least 200 people died, 10s of thousands relocated. My point is not all your flood threats are downstream from you. > Finally, plenty of Dutch houses are built in swamps below sealevel. The technology exists. The dutch have centuries of know how and an entirely separate body to oversee all water management the Rijkswaterstaat. To assume that their model can be easily copied is a massive underestimation of the problem/solutions.

phicoh 5y ago
There is an interesting thing related to the recent floods that happened in Begium, Germany and The Netherlands. The Netherlands spends quite a bit of effort estimating flood risks, and for more important water defenses tries to get the chance of disaster down to about one in 10000 years. However, it seems that this calculation is only done for the lower parts of the country. The Meuse was only taken seriously after a couple of floods in the 1990s (and works were just far enough in The Netherlands that places along the Meuse were mostly fine). However, for smaller rivers, nobody seems to care.