The Mississippi Delta has always been defined by the sediment flow of the river and level of the ocean. Of these two, sediment flow is less important than ocean level – ocean level has varied more than 200 feet over geologic time. With the ocean level rising, the sediment level does affect how fast the delta is inundated. With a full sediment load and no levees, ocean rise would not submerge the delta as quickly. (It is important to remember that the delta was already receding before man started building levees and dams.) But the Mississippi has been leveed along most of its length, limiting both the sediment going into the river and the ability of the river to deposit this sediment over the delta during floods. Dams have also been built on the upper river and on some feeder streams, further trapping sediment. Without these levees, however, much of the delta and the banks of the upper river would be flooded regularly. This would make it impossible for large cities like New Orleans and St. Louis to exist in their current form. This table gives a good view of the periodic floods of the Mississippi:
Some models of the effect of climate change on hurricanes predict fewer storms but stronger storms. While all storms are a threat to the Louisiana coast, it is the large storms that threaten the very existence of cities such as New Orleans. Dr. Jeff Masters’ WunderBlog has excellent discussion of these models and whether the 2010 season is consistent with this theory:
For the nation, the Deepwater Horizon oil well blowout and release was unprecedented in scope,scale, and duration. While the response system established by the Oil Pollution Act of 1990(OPA 90) has effectively dealt with approximately 1,500 oil spill incidents per year since itsenactment, this incident exposed deficiencies in planning and preparedness for an uncontrolledrelease of oil from an offshore drilling operation. The incident also highlighted the differencesbetween the system of response for oil spills and that provided for other emergencies such asnatural disasters and terrorist incidents.
Over the past decade, both public and private sector investment in planning and preparedness forand response to oil spills has decreased. If the public and Congress expect significantimprovements in this Nation’s ability to respond to catastrophic oil spills, additional funding willbe needed for improvements, which include research and development and increasedgovernmental oversight of private sector preparedness and response capability. To be effective,such oversight should begin at the outset of the offshore drilling permit process. This reporturges that planning and preparedness programs be reviewed, and that adequate funding beprovided to enhance oil spill preparedness and response programs so they can effectively addressan offshore Spill of National Significance.
Several areas of the United States are subject to tsunamis, and the coast north of San Francisco through the Canadian border has a history of catastrophic tsunamis. This report from FEMA details the tsunami risk in the United States:
Those who saw the damage from the Hurricane Katrina storm surge have noted that it looks very much like the tsunami damage. While a hurricane surge does not have the initial force of a fast moving tsunami, the wave action during the long period of inundation leads to very similar damage. It is likely that the New Orleans levees will be no more effective than the tsunami walls when the next great storm comes to the Louisiana Coast. As the Japanese learned, it is failing to work with realistic estimates of wave heights, not construction, that ultimately determines the usefulness of flood walls.
Hurricanes Katrina, Rita, and Gustav were relatively dry storms. Had they been wet storms like Allison, the damage to Louisiana would have been much greater. If New Orleans received the 39 inches of rain that Houston received during Allison, it would overwhelm the pumps and would flood nearly as badly as with Katrina.
“Tropical Storm Allison produced severe storms, torrential rainfall, and associated flooding across the southern and eastern sections of the United States from June 5 to June 18, 2001. After making landfall near Galveston, Texas, on June 5, the storm moved inland to near Lufkin, Texas. Allison drifted back into the Gulf of Mexico on June 9, turned to the northeast, and made landfall again on June 10 near Morgan City, Louisiana. After causing 24 deaths in Texas and Louisiana, Allison moved across southern Mississippi, southern Alabama, southwest Georgia, and northern Florida, causing 9 more deaths. By mid-week, Allison stalled over North Carolina and produced more heavy rainfall and flooding before tracking northeast along the DelMarVa Peninsula and moving off the New England coast on June 18. Seven additional deaths occurred in Pennsylvania and one in Virginia. Figure 1 shows the path of Tropical Storm Allison, and Figure 2 shows the associated rainfall. Tropical Storm Allison caused more damage than any tropical storm in U.S. history, with estimates in excess of $5 billion. Most of the damage and fatalities (22) occurred in Houston, Texas. Storm rainfall totals peaked at 36.99 inches (Port of Houston) in Texas and 29.86 inches (Thibodaux) in Louisiana. Since this was the area of extreme rainfall and greatest impact in terms of damage and fatalities, the report focuses on NWS performance in southeast Texas and southern Louisiana.”
This is a presentation at the University of Oregon Public Interest Law Conference, March 5th, 2010:
The thesis is that coastal restoration is impossible on the Louisiana Coast. The only way to preserve the coastal ecology is to allow the coast to retreat as the ocean rises. Continuing to support coastal restoration empowers interest groups whose long term goal is to use levees to hold back the ocean. This will destroy the coastal wetlands, while increasing the costs of the eventual destruction of coastal infrastructure by ocean rise and hurricanes. The Black Swan is that environmental groups cannot accept that the dynamic world of ocean rise makes traditional notions of restoration impossible.
By Kathy Chu, USA TODAY
DAUPHIN ISLAND, Ala. — This island’s website couldn’t be blunter: “Dauphin Island is in a precarious position of being a barrier island, in essence an overgrown sandbar. This gives us a potential of being a disaster in the making. We have been hit by numerous hurricanes, Ivan, Frederic, Georges, Danny and many more!”…
The real irony is the claim that New Orleans is different from the other places built in high risk zones – the problem in New Orleans is that the feds do not spend enough on levees to protect the city. Once the feds begin to subsidize high risk development, it is considered an entitlement and it is the feds fault, not the locals for the bad land use decisions.
The blog cover image is a picture I took at Waveland, MS, looking toward Biloxi, after Hurricane Katrina. More of my Katrina images are available at: www.epr-art.com
The LSU Law Center has an active environmental law society:
Coastal law brings together many legal specialties, including property law, oil and gas law, federal and state environmental law, public health law, and aspects of national security law. But law alone is not enough. Developing effective coastal policy also requires understanding the natural processes that shape the coast and its future. These include geology, meteorology, climatology, environmental science, ecology, and risk assessment theory. There are several nationally prominent scholars working on these topics at LSU. There is also a local community of experts with experience in the private sector and at government agencies. Several are participants in this blog. The LSU Law Center and other departments on the LSU campus offer a broad selection of courses to students interested in coastal law.