Levee Threats Gaining Attention

May 23, 2007

Recent levee failures in Colorado and Missouri have provided still more examples of the fragility of thousands of miles of US levees.

Major disasters in which levee failures have played a role in the past 15 years have highlighted problems with levees, some of which are 150 years old. But potential future disasters - possibly triggered by floods, hurricanes, earthquakes, or mundane problems such as poor levee maintenance - still loom large, especially since there is scant national, state, or local information on basics such as location, condition, and level of flood protection provided.

Levee failures can threaten lives, property, drinking water, crops, and natural habitats, and can cause massive economic and social disruption, as seen with the disasters in New Orleans in 2005, and in the Midwest along the Missouri and Mississippi rivers in 1993-1994, during which 840 of Missouri's estimated 1,456 levees were damaged, and all but two of the state's 114 counties suffered flood damage. Missouri State Emergency Management Agency (facts on the '93-'94 floods).

In early May 2007, Missouri, which still has no comprehensive inventory of its levees, was the scene of additional levee failures. Near the village of Big Lake, in northwest Missouri's Holt County, high flows helped cause breaches in five major levees along the Missouri River, and four smaller ones along the Tarkio River and Tarkio Creek (Joplin Globe, May 9, 2007).

Several dozen levees in Missouri eventually breached or overflowed in the next few days in this and other parts of the state during a multi-day rain storm (CBS News and Associated Press, May 11, 2007).

In Pueblo, CO, Fountain Creek, which was well below flows typically of major concern, breached an old levee and damaged numerous homes and businesses. Some of the dislocated citizens had warned of a potential crisis for years, after the private land behind the levee had been excavated during construction of a Wal-Mart. However, government officials say they had no authority to regulate the excavation. This and other potential causes, possibly including another in a long line of shifts in the meandering creek's location, remain under investigation (Pueblo Chieftain, May 9, 2007, by Jeff Tucker, and May 11, 2007, by Jeff Tucker and Margie Wood).

The post-disaster assessments of the levee breaches in CO and MO have raised a host of issues common throughout the US that have been known for some time, but which have been only minimally addressed.

One of the most important problems is that many levee locations are largely unknown and unmonitored. Levees have been built by private parties; railroads; utilities; farmers; districts set up for levees, flood control and other purposes; local, state, or federal government agencies; and others, often with little or no review, permitting, or subsequent inspections or maintenance. New levees are in the pipeline, and may be built under similar circumstances.

When they are built, levees should be a measure of last resort, say some observers, after steps such as accurate floodplain designations, adoption of development restrictions, management of runoff from developed areas, relocation of existing development from flood-prone areas, approval of intergovernmental agreements in larger watersheds, and wetlands revitalization, have been implemented. But a range of government regulations and financial and insurance incentives instead often make levees a leading option for many local governments, says the Association of State Floodplain Managers' (ASFM) Larry Larson, 608-274-0123.

Another significant problem is that new development is occurring in agricultural areas that had been protected by levees. But those levees were typically built to accommodate far less than the 100-year flood usually designed for in developed areas. Other levees may have been initially designed to withstand a 100-year flood, but new development over the years may have drastically increased area runoff, rendering them ineffective.

Should the extreme weather events predicted to accompany climate change occur in coming years, that may also invalidate the calculations used to determine how effective a levee may be, as problems such as subsidence, erosion, and increased runoff undermine these structures.

Addressing all these problems will be hugely expensive, though there are no cost estimates, in part because no state has a full inventory of existing locations and conditions. However, some, such as IL, KS, MS, and ND, say they are a little ahead of the curve, according to recent surveys by ASFM and the Association of State Dam Safety Officials. ASDSO: Sarah Mayfield, 859-257-5140, or Alan Lulloff, 608-274-0123.

Others, such as California, have begun to recognize they have serious problems. On Feb. 24, 2006, Gov. Arnold Schwarzenegger declared a state of emergency, and triggered an extensive inventory, inspection, and repair process. Release and CA Dept. of Water Resources Levee Repair.

Some of the existing levees in the US have been authorized and monitored by the Corps of Engineers. A partial survey of these resulted in the identification in early 2007 of 122 that are particularly hazardous (see TipSheet of Feb. 14, 2007).

The Corps has recently begun a risk assessment of all federal levees (plus many that meet federal standards), which is expected to take until at least 2013 to complete. These levees stretch at least 13,000 miles, but still are just a fraction of all US levees. For instance, California alone has at least 10,000 miles of nonfederal levees. Corps: Peter Rabbon, 530-756-1104; fact sheet on the National Levee Safety Program.

The Federal Emergency Management Agency (FEMA) has begun an effort to improve its knowledge of some levees, update details on their flood protection capacity, and redraw some floodplain maps: Levees Web site. FEMA and the Corps say they are coordinating with each other.

On the political front, one effort to spur improvements in baseline information, funding, insurance, inspection, repair, and related work occurred in 2006, with introduction of HR 4650 in the US House (search for bill number here). That bill made some headway, but did not get enacted. A similar effort is being made this year, with the introduction of HR 1587 in March 2007.

Portions of those proposals may make their way into other legislation introduced in the next month or two, likely derived in part from the work of the US House Committee on Transportation and Infrastructure, which held a hearing May 8, 2007 ("National Levee and Dam Safety Programs"). Presenters included the Corps of Engineers, FEMA, the American Society of Civil Engineers, the Association of State Dam Safety Officials, the Association of State Floodplain Managers, and the National Association of Flood and Stormwater Management Agencies.

Meanwhile, simply finding levees in your audience area will likely take some digging. There may be hints of levee locations on official floodplain maps, or detailed topographic maps, such as those produced by the US Geological Survey. State, county, and city officials are other possible information sources, as are local levee or flood control districts. Road, railroad, and utility personnel may also be aware of levees, as may farmers, developers, long-term residents, or others in the community.

Some or all of these sources may also be able to give you an inkling which, if any, of these levees may pose a significant hazard, if such an evaluation isn't available from any of the other sources mentioned already, or the ones that follow (including the last three recommended by Mark Schleifstein):