responsibility. The tens of thousands of miles of other levees across the nation are owned by and are the responsibility of local governments, member organizations (e.g., special levee districts), or private entities. Some of these levees were constructed by the Corps of Engineers and turned over to communities.

For levees constructed by the Corps, the minimum nonfederal (local) share is 35 percent. Local cost-share requirements can represent a considerable challenge to financially struggling communities that are seeking structural flood protection. As a result, many communities consider less expensive alternatives for flood risk management, which could include options such as relocations, zoning restrictions in floodplain areas, building codes, and other ‘nonstructural measures’ (see Box 3-10). Such flood management alternatives are not new. The late geographer Gilbert White, for example, and many other scholars and practitioners, for decades encouraged less intensive floodplain development and alternatives to large civil works structures to combat floods (see White, 1945, 1960).

Despite some successes, these types of alternatives have not always received full consideration. Federal water project planning guidance, for example, may not always have encouraged unconventional, nonstructural alternatives (see Box 3-10; also see NRC, 1999). In any event, a resource constrained environment will cause communities and others to carefully consider less expensive alternatives to flood risk management, which require fewer long-term OMR costs, and which may also enhance environmental benefits. As stated in this committee’s 2011 report, “given current budget realities, the nation may have to consider more flexible, innovative, and lower cost solutions to achieving water-related objectives” (NRC, 2011).

Flood Risks, Infrastructure, and National Flood Policies

Despite billions of dollars invested in flood control structures by the Corps of Engineers, the U.S. Department of Agriculture, and the Department of the Interior, and despite a National Flood Insurance Program enacted in 1968, U.S. flood damage losses increased during the twentieth century (National Weather Service, 2012).

This trend of increasing national flood damage losses over time has continued into the twenty-first century (Figure 3-5). The late geographer Gilbert

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