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Behind the Levees
Levees were first built in the United States more than 150 years ago. Many of the earliest American levees were built by farmers to protect their crops from floods. Since then, levees also have been constructed to protect urban areas. Typically, these more recent levees have been built to the rigorous standards of the U.S. Army Corps of Engineers (USACE). However, as rural areas have undergone development and urbanization, farms increasingly have been replaced by homes and businesses. People who live and work behind levees may be relying on an insufficient level of protection from flooding. Across the country, there are now tens of thousands of miles of river and coastal levees that affect millions of people. It is important for them to understand the risks associated with being behind levees and the steps they can take to protect themselves and their property from flooding. In particular, these people need accurate assessments of their current degree of protection and the scope of flood damage should their levees fail. A Calculated Risk No levee can provide full protection from flooding. Even the best flood control system or structure cannot completely eliminate the risk of inundation when flood-swollen rivers or lakes overflow. Although all levees are designed to provide a specific degree of protection based on projected flood depths, unexpectedly large floods can cause them to be overtopped or even fail altogether, as happened in New Orleans after Hurricane Katrina made landfall in 2005. Because levees deteriorate over time, they require regular inspection and maintenance and periodic upgrades to retain their structural integrity and continue to provide the degree of protection for which they were designed. Maintenance can become a serious challenge, and a great expense, as a levee system gets older. When levees that have been insufficiently maintained fail, the consequences can be catastrophic, with more significant damage than if the levee had not been constructed in the first place. Unfortunately, assessing the safety of levees is difficult because information about their locations, ages, structural integrity, and certification status often is outdated or missing altogether. Levee Accountability Who owns levees? A levee owner can be a Federal or State agency, a water management or flood control district, a local community, a levee district, a private business, or an individual. Who operates and maintains levees? A Federal or State agency, an agency created by Federal or State law, or an agency of a community participating in the NFIP is responsible for operating and maintaining levees. Who evaluates the safety of a levee? Levee safety evaluations are the responsibility of the levee owner. What is FEMA's role? FEMA's authorizing legislation makes it responsible for identifying flood risks in areas behind levees. This is accomplished by flood risk analysis and flood hazard mapping projects, which include updating the nation's flood hazard maps through the Map Modernization Program. FEMA does not design, operate, examine, certify, or maintain levee systems. Nor does FEMA determine how a structure or levee system will perform in a flood event. However, the agency is responsible for establishing minimum design, operation, and maintenance criteria that must be met for a levee to be recognized as providing flood protection against the 1-percent-annual-chance flood. And, because FEMA's Flood Insurance Rate Maps (FIRMs) display zones of relative flood risk, FEMA recognizes on its FIRMs only those levee systems that have met and continue to meet these minimum standards. It is FEMA's job to set levee safety standards. However, because FEMA is not empowered to examine or analyze structures to determine their performance in a given flood event, it is the levee owner's job to provide documentation to show that a levee meets current design, operations, and maintenance criteria. Levee Safety and Flood Insurance FEMA is updating the nation's flood hazard data and maps through its Map Modernization Program. According to Provisionally Accredited Levees, a new FEMA publication, approximately one quarter of the counties that FEMA is remapping have levees shown on their FIRMs.
What happens if a levee's owner cannot prove that it meets FEMA's 1-percent-annual-chance criteria? In such cases, FEMA revises the FIRM currently in effect to show that the land behind the levee has insufficient protection from flooding and is, therefore, a high-risk Special Flood Hazard Area. This action puts property owners on notice that they are in greater jeopardy of flood loss. At policy renewal time, it also results in higher flood insurance premiums to reflect the increased flood risk. The 1-Percent-Annual-Chance Flood According to the NFIP's Flood Insurance Manual, the 1-percent-annual-chance flood is one that has a 1-percent chance of being equaled or exceeded in any given year. Formerly called the "100-year flood," the 1-percent-annual-chance flood is synonymous with "base flood." A 1-percent annual chance of flooding may not seem like much of a gamble, but unpredictable weather conditions, recent upstream development, or deteriorating levees can dramatically increase the chances of flooding in areas that people thought were safe. FEMA Guidance The devastation caused by Hurricanes Katrina and Rita in 2005 brought the issues of levee policy, flood hazard management, and flood insurance to the forefront of public debate and discussion. However, these issues were not new to FEMA. Nearly 20 years before Katrina and Rita made landfall, FEMA established detailed requirements (in Title 44 of the Code of Federal Regulations, Section 65.10) to guide the evaluation of levees and the mapping of levee-affected areas on flood maps. Periodically, FEMA disseminates information about levee safety and certification and about the procedures used for showing the flood risk behind levees on Flood Insurance Rate Maps. For example, FEMA's comprehensive Guidelines and Specifications for Flood Hazard Mapping Partners provides guidance for ensuring standard levee evaluation and mapping practices. And, less than 2 weeks before Hurricane Katrina hit the Gulf Coast last year, Mitigation Division Director David Maurstad issued Procedure Memorandum 34: Interim Guidance for Studies Including Levees to all FEMA Regional Offices and Mitigation Division Directors. This guidance reemphasized FEMA's 20-year-old levee policy and regulations and provided additional direction to help communities protected by levees meet Federal safety standards. Several weeks after Katrina made landfall, Maurstad issued Procedure Memorandum 43: Guidelines for Identifying Provisionally Accredited Levees. This document clarified the procedures for documenting flood risk (see below). Because gathering the necessary documentation can take time, FEMA is allowing owners of eligible levees 2 years to provide evidence of the levee's status. During that time, the levee will be shown on the flood map as provisionally accredited, and the area behind it will be shown as having a moderate flood risk. Guidelines for Identifying Provisionally Accredited Levees FEMA is working closely in coordination with the USACE to review and accredit levees in the United States. On September 25, 2006, FEMA issued Procedure Memorandum 43: Guidelines for Identifying Provisionally Accredited Levees, which explains that, because the procedures for documenting flood risk can be a time-consuming process, levee owners will have up to 24 months to obtain and submit necessary data and documentation. In the meantime, the levee will be considered "provisionally accredited" and most or all of the area behind the levee will be designated Zone X (shaded) on the FIRM. A note clarifying the provisional nature of this zone designation also will be shown on the FIRM. On September 26, 2006, the USACE issued a memorandum entitled Policy Guidance for the Prioritization of FY 07 Inspection of Completed Works (ICW) Operations & Maintenance, General (O&M Gen), Mississippi River and Tributaries (MR&T) and Flood Control & Coastal Emergencies Inspection Accounts. This memorandum, developed in collaboration with FEMA's, provides inspection policy guidance on levee systems that are in the USACE's programs. The memorandum helps clarify the USACE's and FEMA's responsibilities for notifying levee owners of the condition of their levees and the data required to accredit levees on FEMA's flood maps. Accreditation Doesn't Guarantee Protection Communities that join the NFIP are required to adopt floodplain management ordinances to minimize damage to homes and businesses located in Special Flood Hazard Areas. In areas behind levees that are mapped as Special Flood Hazard Areas, the NFIP requires all new and substantially improved buildings to be constructed to or above the elevation of the 1-percent-annual-chance flood. In areas behind levees that are mapped as low- to moderate-risk areas, no NFIP floodplain management requirements apply. However, appropriate precautions are still encouraged as the risks for overtopping or failure of the levee remain. People who live or work behind levees must understand the risks they face for flooding. For this reason, FEMA recommends flood insurance for all properties behind levees. In addition, FEMA maps carry a warning that overtopping or failure of the levee, dike, or other flood control structure is possible, and that flood insurance and adherence to evacuation procedures are strongly recommended. For more information, visit the "Levees" page on the FEMA website. There you will find the requirements for "Mapping of Areas Protected by Levee Systems" outlined in Title 44 of the Code of Federal Regulations, Section 65.10. In addition, you will find procedures for levee accreditation in FEMA's Guidelines and Specifications for Flood Hazard Mapping Partners-Appendix H: Guidance for Mapping of Areas Protected by Levee Systems, Procedure Memorandum 34: Interim Guidance for Studies Including Levees, and Procedure Memorandum 43: Guidelines for Identifying Provisionally Accredited Levees. |
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Last updated on February 1, 2007
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