Sunday, May 15, 2011

Bigger, stronger levees are not the answer.

Thanks to Jon Remo for this guest post.

As the Mississippi River Flood of 2011 reaches the Gulf of Mexico much attention has been paid to the system of levees, floodwalls, flood retention dams and floodways constructed under the Mississippi River and Tributaries Project (MR&T) after the "Great" Flood of 1927.  It appears the U.S. Army Corps of Engineers (USACE) and the Mississippi River Commission have successfully used the flood control tools of the MR&T project to protect the Mississippi River Delta (Lower Mississippi River Floodplain) from yet another potentially catastrophic flood. The MR&T project has endowed the Lower Mississippi Valley with the most extensive and likely the greatest flood protection system in the United States.  Some have estimated that the system of levees and floodways can protect the majority of the Mississippi River Delta from up to the 750-year flood.  However, as we have seen from media reports, not all of the Delta's inhabitants benefited from the system’s protection and thousands of others suffered from intentional flooding as emergency floodways were activated.

The USACE estimates over $13.1 billion have been spent on the MR&T project since 1928 and remind us that the project is not slated for "full" completion until at least 2030.  The Corps likes to trumpet their estimated 24 to 1 cost benefit ratio for this project.  While this benefit sounds impressive, the economic analysis does not account for the maintenance or operation of the system, estimated today to be at least $130 million annually, flood fighting costs, or other environmental externalities (USACE, 1998).   Despite the cost, the success of the MR&T flood control system has renewed calls for bigger and stronger levees for many flood prone areas.  However replication of such large and extensive flood control works elsewhere in the United States has proven economically and politically infeasible and unsustainable.

Efforts to replicate the MR&T style of structural flood control, even in the heyday of these projects  (the 1930s to World War II and again after the war into the 1960s), outside the lower Mississippi River Valley were often scaled back to lower protection levels (generally 100 to 500-year flood protection for urban areas and 50-year or less flood protection level for agricultural areas) because of costs.  The cost of constructing many levees was borne largely by the Federal Government with little or no local contribution.  However, once completed, the Federal Government turned these levees over to local levee and drainage districts which were put in charge of collecting taxes for the maintenance of the levees and associated flood infrastructure.  In many areas there was not a sufficient tax base to support proper maintenance.

The thinking when the levees were built was people and business would move into the newly protected areas and a tax base for support of these structures would materialize. This has often not been the case, particularly in the agricultural levee districts. However, underfunding of levee maintenance is not exclusively a rural issue.  Underfunding of  levee and floodwall maintenance in urban areas is common.  As a result, many levees and floodwalls (hundreds to thousands of miles of them) throughout the United States have been deemed by the USACE as either minimally acceptable or unacceptable (i.e., the levee would not perform as designed) condition.  Under Public Law 84-99 (PL 84-99), levee sponsoring agencies that fail to live up to maintenance obligations are classified as inactive and become ineligible for federal levee repair and assistance funds. Maintenance and operating costs are frequently a financial challenge for floodplain communities, and these costs are rarely considered in cost-benefit calculations for levee projects. For example, a recent estimate by the USACE found that up to $500 million is needed to address critical maintenance issues for three levees (Wood River, Chain of Rocks, and Metro East) along a 50 mile stretch of the Mississippi River near St. Louis.


Recent cost benefit studies by the USACE have underscored that large scale levee enhancement or expansion are not cost effective. For example, the Upper Mississippi River Comprehensive Plan (UMRCP; USACE 2008) looked at the costs and benefits of a number of different levee and floodplain management strategies with the goal of reducing flood damages along 970 miles of the Upper Mississippi River (UMR).  Plan H of the UMRCP, with an estimated cost of $3.9 billion, proposed adding 500-year levees to both urban and agricultural areas along almost all of the UMR.  However, despite Plan H  benefit/cost ratio of 0.05 (5¢ of benefits per $1.00 invested), it was endorsed by the Mississippi River Commission and floodplain stakeholders and continues to enjoy considerable local support and political play each time Federal stimulus or other legislative action has been considered to fund this project.

Despite a bias toward structural flood control measures, the UMRCP did consider a plan, Plan J, which called for the removal of all agricultural levees and using buyouts for homes not protected by levees while maintaining the 500-year protection level in urban areas.  Plan J had an estimated total cost of $3.2 billion which is $0.7 billion cheaper than protecting everyone to the 500-year flood level. This plan would have significantly reduced the flood exposure along the UMR floodplain and decreased the flood risk in urban areas because floodwater would have more area in the floodplain to be stored lowering the water heights on the urban levees.  In contrast, Plan H would have  promoted further floodplain development, increasing flood exposure, increased flood levels, and consequently higher flood risk for the urban levees because of the reduction in floodplain storage created by the higher levees protecting agricultural areas.

Unfortunately, Plan J has received little support from floodplain stakeholders and their political representatives.

Elsewhere around the world and in forward thinking regions within the United States, officials and stakeholder groups are either working toward or have implement plans similar to the UMRCP Plan H.  For example, the Dutch government has fundamentally shifted its approach to flood control to a policy of “more room for the rivers,” meaning creating new storage and conveyance space rather than continuing to raise the levee. On the Meuse River, France, Germany, Belgium, Luxembourg, and the Netherlands adopted the Meuse High Water Action Plan, focused on land use activities from a water perspective, longer storage and slower release, and space for the river.  These programs are not purely academic proposals. Since 1988, the Integriertes Rheinprogramm of the state of Baden-W├╝rttemberg, Germany, has reduced peak flood stages to 1950 levels by adding 212 million m3 of storage on the floodplain. In the Netherlands, the “Room for the Rhine” doctrine was adopted in 1997, and the Dutch government has dedicated 3 billion to a broad toolbox of levee alternatives (Pinter, 2005).


In the U.S., after last years’ devastating flood on the Cumberland River, Nashville is planning to expand its current greenway along the river which will provide increased water storage and protection from floods.  The program Nashville Naturally includes goals to increase the metro park system by 30%, protect more than 10,000 acres of floodplain and other sensitive natural areas and establish large-scale preserves in every bend of the Cumberland River.  In 1997 Pierce County, Washington set back nearly two miles of levees along the Puyallup River; this action  reduced flooding in the City of Orting, Washington during two recent floods in 2003 and 2006.

Scientists, engineers, floodplain managers, and decision makers in the U.S.  have realized for decades that the optimum strategy for reducing flood losses is to limit or reduce infrastructure on the floodplain. However, most federal flood control policy continues to encourage floodplain development by financing construction and enhancement of levees, further underwriting the risk of flooding, or eliminating incentives for responsible local decision-making. Federal flood control spending disproportionately supports the construction of levees and dams, encouraging greater floodplain development.  In areas where extensive development has occurred we will need to maintain adequate flood protection.  In areas that are relatively undeveloped we must resist attempts to expand or enhance flood protection because it only increases future flood risk and history has shown it is not fiscally sound nor in most places sustainable without continuous and substantial subsidy from the Federal Government.

Dr. Jonathan Remo is a Post Doctoral Research Fellow and Adjunct Assistant Professor at Southern Illinois University, Carbondale.  His areas of research and expertise include fluvial geomorphology, hydrology, hydraulic modeling, river management, flood loss modeling, and pre-disaster mitigation planning. His research and professional projects have been supported by the National Science Foundation, U.S. Geological Survey, the U.S. Army Corps of Engineers, the Federal Emergency Management Agency, Illinois Emergency Management Agency, and the National Commission of Energy Policy.

Illustration:  Nineteenth century floodfighting in Louisiana and the evolution of levees there through 1914, from USCE.

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