The Corps estimated that about 1,100 of the 1,358 nonfederal levees in the area covered by the five Corps districts involved in the 1993 flood failed to keep the flood out of the areas they were designed to protect or were otherwise damaged. Objectives, Scope and Methodology

The Ranking Minority Member of the Subcommittee on Water Resources and Environment, House Committee on Transportation and Infrastructure, and Representative William L. Clay of Missouri asked GAO to review the extent to which (1) the Corps’ flood control levees prevented flooding and reduced damage during the event; (2) these federal levees increased the height of the flooding and added to the damage; and (3) federal, state, and local governments exercise control over the design, construction, placement, and maintenance of nonfederal levees. Most Corps Levees Performed as Designed and Prevented Significant Damage

According to the Corps, 157 (81 percent) of the 193 Corps levees located in the area affected by the 1993 flood prevented rivers from severely flooding about 1 million acres. Another 32 Corps levees withstood flood flows until the water exceeded their design capacity and overtopped the levees. The Corps estimated that flooding at the 36 levees caused about $450 million in damage. Only four levees allowed floodwater to enter the protected floodplain before the levees were overtopped. This study found that the 1973 flow rate of about 851,100 cfs produced a flood elevation about 7.9 feet higher than it did during the base period. Local governments usually exercise control over nonfederal levees in response to requirements of the National Flood Insurance Program and state regulatory programs. Conclusions

While no comprehensive federal program regulates the design, placement, construction, or maintenance of nonfederal levees, control over nonfederal levees is exercised through various federal programs for regulating navigable waters and wetlands and for providing flood insurance and disaster and emergency assistance.
Why GAO Did This Study

Pursuant to a congressional request, GAO examined the operations of levees involved in the 1993 Midwest flood, focusing on: (1) whether the Army Corps of Engineers' flood control levees prevented flooding and reduced damage or increased the flooding and added to the damage; and (2) the governments exercise control over the design, construction, placement, and maintenance of nonfederal levees.

What GAO Found

GAO found that: (1) 157 of the 193 Army Corps of Engineers levees found in the areas affected by the 1993 flood prevented rivers from flooding and $7.4 billion in damages; (2) 32 of the Corps levees withstood floodwaters until the water rose above the levees and overtopped them; (3) 4 of the Corps levees allowed water into protected areas before their design capacity was exceeded; (4) the Corps estimated that the breaching of these levees caused about $450 million in damages; (5) although levees allow floodwater to rise higher than it normally would because they confine a flood to a portion of a floodplain, the Corps believe that its levees have the net effect of reducing flooding; (6) no federal programs specifically regulate the design, placement, construction, or maintenance of nonfederal levees, however, flood insurance and disaster assistance programs may exercise control over certain levees; and (7) 17 states and various local governments have programs to regulate levees, many of which are in response to the requirements of the National Flood Insurance Program.