The way forward

There are as many as 145,000 miles of levees in the United States, according to the U.S. Army Corps of Engineers. Most are operated by local authorities, with varying safety standards. Here are ways that experts suggest strengthening levee systems: Build to the 500-year flood

Larry Larson, director emeritus of the Association of State Floodplain Managers, said the organization recommends building levees to withstand at least a 500-year flood, an event with a 0.2 percent chance of occurring in a given year. Currently, many are built to the 100-year standard. Plan for overtopping

Larson suggests designing levees so that one section can be overtopped without causing the entire structure to crumble. That section would be slightly lower than the rest of the levee and possibly armored with concrete on both sides to prevent erosion. Take risk into account

The Army Corps supports risk-based levee design. Under that philosophy, engineers take into consideration what a levee will protect rather than applying a single standard in all cases. A levee that protects lives would be built to a higher standard than one that safeguards agricultural land, for example. Fund a safety program

The National Committee on Levee Safety, created by Congress in 2007, recommended development of a nationwide safety code incorporating the best engineering practices and design standards, to be updated at least every 10 years. So far, no national standards for levee systems have been established.