Levees and the National Flood Insurance Program: Improving Policies and Practices (2013)Water Science and Technology Board
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In recent years, extreme storms and hurricanes have caused increasingly disastrous flooding along U.S. rivers and coastlines, with much of the damage occurring when levees failed or were overtopped by water. This report examines how FEMA National Flood Insurance Program assesses, mitigates, and insures against flood risk behind levees, and how the program communicates that risk to the public. FEMA needs an updated approach to analyze and manage flood risk to give public officials and individual property owners a more precise idea of the risks they face, the report finds. Because no levee completely eliminates flood risk, more effective communication is needed to increase awareness and encourage communities behind levees to use multiple methods to manage flood risk.
- In analyzing flood risk, the National Flood Insurance Program should move to a modern risk-based analysis that uses 21st century computational and mapping techniques to produce state-of-the-art risk estimates for all areas vulnerable to flooding. Such an approach would give individual property owners a more accurate view of the risks they face. It would also assess how well levee systems are likely to perform, informing communities of their levee systems' limits and potential vulnerabilities – information that current analyses do not provide.
- While purchasing flood insurance is an effective way for property owners behind levees to deal with financial risk from floods, at this time there is no sound reason to institute mandatory purchase of flood insurance in areas behind accredited levees. The mandatory purchase requirement has not been effective at achieving widespread purchase of flood insurance in areas of the floodplain without levees; extending it to areas with levees – where the level of flood risk for many properties is unknown and where the challenges of risk communication are great -- would not be a prudent step. Once the modern risk analysis has been put in place and matures, FEMA should study whether the mandatory purchase requirement is necessary throughout flood hazard areas and behind levees.
- Because levees can reduce but not eliminate the risk of flooding, FEMA should encourage communities behind levees to use multiple methods to reduce risk and increase awareness of these risks. In addition to structural methods such as levees and floodways, communities should consider non-structural techniques, which include flood-proofing, elevating or relocating structures, evacuation planning, and the purchase of flood insurance.
- The Levee Analysis and Mapping Procedure (LAMP), a new approach proposed by FEMA to help assess the flood risk in areas protected by levees, is a reasonable first cut at dealing with the potential contributions of levees that do not meet FEMA's standards for protection against the one percent annual chance flood. However, implementing LAMP would divert effort away from a move to a modern risk-based approach. FEMA should move directly to more modern risk-based analyses for dealing with areas behind levees and not implement the LAMP approach. Interim steps to deal with non-accredited levees are proposed in the report.
- Using a more modern risk analysis would help FEMA set insurance rates in ways that more appropriately reflect flood risk. By employing advances in hydrology, meteorology, geotechnology, and engineering, such an analysis could more precisely calculate the probability of water inundation levels and the associated damage estimates throughout an area in a graduated fashion.
- An important part of managing flood risk is to ensuring that communities understand the risks they face. FEMA and others involved in communicating about flood risk at all levels should incorporate contemporary risk communication principles into their efforts. FEMA should communicate flood risk through a collaborative approach that works with and provides strong support to local communities.
- One challenge to flood risk communication at the federal level is uncoordinated messaging. Developing one federal message, using consistent terminology, transparent data, and open discussion about flood risk is critical to inform the affected communities who, in turn, communicate and manage risk at the local level. FEMA should assume a leadership role in providing direction for research, development, and release of flood risk communication products and maps.
- FEMA and the US Army Corps of Engineers are challenged by different approaches to risk analysis. Technical and programmatic differences in the evaluation of flood hazards and levees systems can compromise inter-agency communication and cause confusion and frustration in the local community. FEMA and the U.S. Army Corps of Engineers should jointly develop a common, risk-based approach to levee assessment in a timely manner, and apply this approach to all levees assessed by the two agencies. This includes a joint methodology, procedure, and where feasible, the sharing of models and other risk analysis tools.