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Large Scale Infrastructure to Protect against Flooding and Sea Level Rise, images from UK Environment Agency

On Tuesday, August 28 Hurricane Isaac sparked fears of a repeat of Hurricane Katrina by making landfall as a Category 1 near the Mississippi River. While the barriers in New Orleans held, a levee in southeast Louisiana was overtopped, causing devastating flooding in Plaquemines Parish. We wish all of the victims a speedy recovery.

Without some form of climate resilience coupled with greenhouse gas reduction, events like this will likely become more common. The global mean sea level has risen by some 20 cm since 1880, raising the launch pad for hurricanes, storm surges, and tsunamis. The Intergovernmental Panel on Climate Change (IPCC) projects that during the 21st century, sea level will rise at least another 18 to 59 cm (7.1 to 23 in), and extreme precipitation events are very likely to increase.

This week’s entry focuses on large-scale infrastructure to protect against flooding and sea level rise. Many great examples come from current projects in the Netherlands; roughly two-thirds of its area is currently vulnerable to flooding, while the country is among the most densely populated on Earth. Note large-scale infrastructure adaptation techniques may not be appropriate for many communities; even when deployed, these techniques should be coupled with other measures such as green infrastructure that reduce stormwater runoff and energy usage.

 

Large-Scale Infrastructure to Protect Against Flooding and Sea Level Rise

Dams and flood control

Dams store floodwaters during high precipitation periods and then release the stored water gradually to reduce the likelihood of damage to the community at risk. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate low-carbon electricity. At 22.5 GW, the Three Gorges Dam in China is projected to be the largest in total generating capacity of any power plant in the world. By comparison, the United State’s Hoover Dam has a total generating capacity of 2.1 GW. Dams should be sited carefully; side effects include land use, population displacement, and increased potential for landslides. Where a dam, reservoir, or river may overflow, floodways, spillways, or channels are constructed to carry these flows around the community or region. For instance, during the Mississippi River floods in April and May 2011 the U.S. Army Corps of Engineers relieved downstream flooding and saved Cairo, Illinois by opening spillways.

Levees, floodwalls, barriers, and similar structures

These structures are designed to prevent floodwaters, storm surges, or other flows from reaching areas that are at risk. Flood barriers are almost always part of a larger flood protection system consisting of floodwalls, levees (also known as dikes), and other constructions and natural geographical features. In the absence of dam and levee failures, these structures will greatly reduce energy expenditure to rebuild in the wake of a disaster. However, negative side effects include cost, potential of failure, visual impact, constant pumping of rain and groundwater within the walled areas, and enhanced erosion. Broadening dam and levee safety programs to consider community- and regional-level priorities in decision making can help reduce the risk of, and increase community resilience to, potential dam and levee failures. Great examples include the Thames Barrier in London as well as Fox Point Hurricane Barrier in Rhode Island, the first hurricane storm surge barrier in the U.S. (courtesy of Josh Foster, Oregon State University). Smaller scale structures also exist. Corné Rijlaarsdam, the designer of Dutchdam floodbarriers, sent us a video on their product.

 

Floating Infrastructure

Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less commonly as a man-made phenomenon, such as Uros island in Lake Titicaca. To combat sea level rise, the Maldivian government has signed a deal with Dutch Docklands International, an architecture firm that specializes in floating developments and infrastructures, to build artificial islands that will be able to rise along with the sea level.



This post is part of CCAP’s blog series, “What Does Climate Resilience Look Like,” which highlights adaptation images from around the world addressing a variety of climate impacts and resilience solutions. Have a climate resilience image to share? Please send us the photo by Twitter, Facebook, or email. (Please include the Who What Where: Who took the photo? What is the adaptation technique? Where is it located?) We are especially interested in examples that advance multiple goals such as GHG emission reductions and sustainable economic development.

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4 COMMENTS

  1. Kelly Klima

    New paper in Climatic Change concludes that adaptation and mitigation are complimentary policies in coastal areas.
    http://www.springerlink.com/content/b7542u085g017843

    Title:
    The effects of adaptation and mitigation on coastal flood impacts during the 21st century. An application of the DIVA and IMAGE models

    Abstract
    This paper studies the effects of mitigation and adaptation on coastal flood impacts. We focus on a scenario that stabilizes concentrations at 450 ppm-CO2-eq leading to 42 cm of global mean sea-level rise in 1995–2100 (GMSLR) and an unmitigated one leading to 63 cm of GMSLR. We also consider sensitivity scenarios reflecting increased tropical cyclone activity and a GMSLR of 126 cm. The only adaptation considered is upgrading and maintaining dikes. Under the unmitigated scenario and without adaptation, the number of people flooded reaches 168 million per year in 2100. Mitigation reduces this number by factor 1.4, adaptation by factor 461 and both options together by factor 540. The global annual flood cost (including dike upgrade cost, maintenance cost and residual damage cost) reaches US$ 210 billion per year in 2100 under the unmitigated scenario without adaptation. Mitigation reduces this number by factor 1.3, adaptation by factor 5.2 and both options together by factor 7.8. When assuming adaptation, the global annual flood cost relative to GDP falls throughout the century from about 0.06 % to 0.01–0.03 % under all scenarios including the sensitivity ones. From this perspective, adaptation to coastal flood impacts is meaningful to be widely applied irrespective of the level of mitigation. From the perspective of a some less-wealthy and small island countries, however, annual flood cost can amount to several percent of national GDP and mitigation can lower these costs significantly. We conclude that adaptation and mitigation are complimentary policies in coastal areas.

    Reply
  2. Kelly Klima

    Sunken Streets:

    Essentially, the road bed is sunken and the sidewalks are raised; normally it’s just a street, but can become a flood control measure when needed.

    These were commonly used in ancient cities: …
    Blog on Italy shows sunken streets in
    * Pompeii
    * Erculeum

    We’re told these “flood way” streets were built in the UK specifically to become flood channels to funnel off storm water…. anyone have the images?

    Reply
  3. Kelly Klima

    Sunken Streets:

    Essentially, the road bed is sunken and the sidewalks are raised; normally it’s just a street, but can become a flood control measure when needed.

    These were commonly used in ancient cities: …
    Blog on Italy shows sunken streets in
    * Pompeii – http://www.eskimo.com/~mikeg/italy_2007/stepping_stone_closed_street.jpg
    * Erculeum – http://www.eskimo.com/~mikeg/italy_2007/sunken_streets.jpg

    We’re told these “flood way” streets were built in the UK specifically to become flood channels to funnel off storm water…. anyone have the images?

    Reply