In a Monday briefing, representatives from the Association of State Floodplain Managers, National Association of Flood and Stormwater Management Agencies, and the Nature Conservancy gathered to discuss the opportunities in the proposed WRDA bill to reduce flood risks and the potential damages from flood disasters.
The nation’s dam and levee system is characterized by low system integration, having been constructed in an ad hoc manner, with little to no regard for the effects beyond the immediate applications. Because dams and levees are often constructed by localities to serve the needs of their constituents, there is no full register of all the existing dams and levees in the United States. Many of the known dams and levees are reaching or exceeding their designed operating age of 50 years, creating a pressing need for a National Levee Safety Program. Recently built dams are constructed to withstand the 100 year flood. However, according to Dr. Professor Mathias Kondolf of U.C.-Berkeley, a house with a 30 year mortgage built in a floodplain area has an aggregate 26 percent chance of being flooded over the course of the mortgage. Since they are living under the protection of a 100 year dam, houses in these areas often do not have flood insurance and have not taken steps to protect themselves, such as elevating the structure, from flood waters. Dr. Kondolf continued on to say that the aim of modern dams is to “filter out the small floods,” but that they do not protect from “the big ones.”
In many areas historically prone to flooding and flood damage, the presence of protective structures has actually drawn increased levels of business and personal development. This risk intensification was borne out in areas damaged by Superstorm Sandy and Hurricane Katrina when levees holding back ocean water failed. Floods, in their natural form, are healthy for and necessary parts of an ecosystem. In fact, without the floods of the Mississippi and Missouri rivers carrying silt and material, the Mississippi Delta around which New Orleans is built would not exist. Disaster arises when a dam or levee is built and people are allowed to build and live in what was the floodplain. When a flood does breach the wall, the costs can be astronomical.
The hazards out flood disasters can be mitigated by analyzing and appropriately managing flood-vulnerable areas. By adopting policies known in the Netherlands as “room for the rivers,” the effects of floods on human activities can be mitigated. Some recommendations in accord with this are to set levees further back from the main flow of water, thus allowing any flood to proceed more naturally, or to designate areas of land that to be used as flood bypasses during times of high flood waters. However, the availability of these lands during dry times can induce development. All representatives present at Monday’s briefing agreed that, as a rule, “non-structural” approaches such as giving the river room, building houses above flood level, and creating natural drainage channels around cities are best suited to provide long-term protection.
Ultimately, WRDA is an essential bill to plan and manage the nation’s waterways and flood preparedness. It is necessary to establish national guidelines for dams and levees, provide money to repair levees, and establish a comprehensive database of levees in the country. Cost-sharing, imposing per-project caps, and creating a national floodplain management plan will allow the legislation to provide the greatest amount of benefit.