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Is "Sea Level Rise Mitigation" A New Engineering Career Field? 2

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SlideRuleEra

SlideRuleEra

Structural
Jun 2, 2003
5,528
Whether global warming is "true", "false", "caused by human activities", or "natural" has been talked about frequently in other forums. Sea level change is often linked to global warming. Unlike global warming, sea level change has been documented by comprehensive real-time data collection. On the US coastline this has been taking place at numerous locations for up to 130 years. Sea levels are increasing. This could be caused by water level rise, land subsidence, or both... the reason does not matter. Here is a typical graph showing the increase at Charleston, SC, since 1921:

Tide_Gauge_i5mf4w.png


Numerous coastal cities are contending with real effects of sea level rise:

Cities-Title-1_hhfgod.png

Cities_nxjr9t.png


Most cities are "talking", "discussing", or "planning" about what to do. To my knowledge only one is acting: Charleston, SC

WorkInProgress_dt0uau.png


The city has no real choice, it is located on a peninsula with adjacent tidal water, small (135,000 population), flat, and low.

WorkInProgress-2_aaxkep.png


Flooding is complex, here are simplified examples:

1) With heavy rain at high tide, storm water drainage does not work... the city floods with fresh water.

2) No rain, but "very" high tide, there is no drainage, sea water floods the city.

3) Engineering solutions only address flooding for a limited time. If global warming is "true", the time is "sooner". If global warming is "false" the time is "later". For planning purposes, would be nice to know the answer.

Problems encountered while searching for a solution include:
Geotechnical​
Environmental​
Civil​
Structural​
Mechanical​
Astronomical (tidal cycles)​
Meteorological (rain, wind driven tide, hurricane storm surge)​
Archeological (unmarked graves, excavated unknown cultural sites, unearthed unexploded ordinance from Civil War artillery bombardment)​
Historic Preservation​

To my knowledge there is no such field of engineering that addresses all of these areas...at least at a level where one Engineer can explain the technical aspects of a proposed sea level mitigation project to "Decision Makers".

If there were such a thing as "Sea Level Rise Mitigation Engineering", perhaps the cities that are "talking", "discussing", and "planning" can be convinced to "act"... jump-starting engineering design, construction, and operation of large scale infrastructure projects that evidence demonstrates are badly needed.

[idea]
[r2d2]
 
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Well, one option is the way Venice went/is going, which is to abandon the lower levels that get submerged. Alternately, we can go the route that the Netherlands and New Orleans went, which is to build dikes and pumps to pump out the overflow; these would be basically miles of dams, so definitely a massive CE job.

Whether there's enough money is different matter altogether.

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Sea levels rise after Ice Ages. Always have, always will. So I've got no beef with the mechanism.

The main reason a lot of cities are flooding now is groundwater extraction, and the installation of storm drains in the ever widening suburbs, and the intentional drainage of estuarine marshlands, which flushes the water straight out to sea instead of replenishing the aquifers and soaking the marshland.

So rather than just sea walls and pumps it looks to me like there might be some benefit in stopping groundwater extraction, and maybe capturing stormwater. Maybe even pumping the land back up by refilling the water table.

Another issue is storm surges, due to ever widening and deepening shipping channels. Perhaps a crafty hydrologist could design some sort of speed bumps in shipping channels that break up the wave patterns (a bit like a hydraulic jump).



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Groundwater extraction cause ground subsidence, not sealevel rises. They are distinct and measurable. The volume of missing groundwater cannot equate to the sealevel rise.

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IRstuff,
That depends on the location, primarily the geology. Groundwater extraction can lower areas by metres, such as it has in Mexico City.
 
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Right, but that's subsidence of the ground, not sealevel rising. The ground subsidence worsens the effect of sealevel rise. Sealevel rise is measured from the mean geoid height, which is independent of the ground level

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Yes, but cities that flood are built on the surface of the ground, not the geoid. We don't really care if the sea level increases per se, if it doesn't flood anything. I was not suggesting that the stormwater adds to the sea level increase by adding water, obviously.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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If the mean ground level is 1m, and the sea rises 2m, and the subsidence was only 0.5m, it's still going to flood. There are houses on the beachfront in California that will be surrounded by water if the sea level rises by more than a meter, and that close to the water to start with, there was never any ground water to be extracted.

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Well, perhaps I should have specified "a lot of cities but not every single bit of coastline". Happy now?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Well it's not really a new area, since improvement of flood defences has been an active engineering field for many years, in fact I worked in that area myself (on the Thames flood defences associated with the Thames Barrier) in the mid-1970's, but it certainly will (or at least should) be an expanding area.

Unlike global warming, sea level change has been documented by comprehensive real-time data collection.
Click to expand...

I don't understand this comment. It seems to me that evidence for increasing temperatures is of a very similar standard to that for rising sea levels.

Doug Jenkins
Interactive Design Services
 
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IRstuff, sorry are you saying that paper I posted has been challenged? Here's the abstract. I don't know about the other examples but Bangkok and Bangladesh are well known for subsidence due to groundwater extraction

. In many coastal and delta cities land subsidence now exceeds absolute sea level rise up to a factor of
ten. A major cause for severe land subsidence is excessive groundwater extraction related to rapid urbanization
and population growth. Without action, parts of Jakarta, Ho Chi Minh City, Bangkok and numerous other coastal
cities will sink below sea level. Land subsidence increases flood vulnerability (frequency, inundation depth and
duration of floods), with floods causing major economic damage and loss of lives. In addition, differential land
movement causes significant economic losses in the form of structural damage and high maintenance costs for
(infra)structure. The total damage worldwide is estimated at billions of dollars annually.
As subsidence is often spatially variable and can be caused by multiple processes, an assessment of subsidence
in delta cities needs to answer questions such as: what are the main causes? What is the current subsidence rate
and what are future scenarios (and interaction with other major environmental issues)? Where are the vulnerable
areas? What are the impacts and risks? How can adverse impacts be mitigated or compensated for? Who is
involved and responsible to act?
In this study a quick-assessment of subsidence is performed on the following mega-cities: Jakarta, Ho Chi
Minh City, Dhaka, New Orleans and Bangkok. Results of these case studies will be presented and compared,
and a (generic) approach how to deal with subsidence in current and future subsidence-prone areas is provided

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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Many coastal cities have built up area using landfill, so there was never that much ground height to start with. Any serious sealevel rise would inundate huge sections of the north and east sides of San Francisco, probably including the Millenium Tower, which already has problems.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Built up land fill? Where did that fill come from? Can we get more?

Can we store stormwater for when we need it? We do that with natural gas.

 
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