Levee Analysis and Mapping Procedure
As indicated in Chapter 2, the examination of levees under the Map Modernization Program identified many levees that no longer met the requirements of Title 44, Section 65.10 of the Code of Federal Regulations (44 CFR §65.10). As a result, the areas behind these levees in the one percent annual chance floodplain were to be remapped as being in the Special Flood Hazard Area (SFHA) and would be subject to the mandatory purchase requirements of the NFIP. In response to congressional requests, the administrator directed FEMA staff to develop an approach to mapping nonaccredited levees that would reflect any risk reduction and the commensurate rates that nonaccredited levees might afford the communities. In March 2011, FEMA issued a public notice stating that
The new approach [being developed] will provide a more precise assessment of flood risk in areas impacted by levees. Because the new modeling methods may affect the treatment of a levee, FEMA will temporarily withhold issuing flood risk study final determinations for those communities whose levees do not meet accreditation requirements of 44 CFR §65.10. This temporary delay will allow FEMA to give proper consideration to levees under the new modeling procedures. (FEMA, 2011b)
Between, March 2011 and February 2012, FEMA developed and circulated for public comment the Levee Analysis and Mapping Procedure (LAMP) to identify where risk reductions might occur from evaluation of the performance of levees below the one percent annual chance standard. The LAMP was designed to be implementable without statutory or regulatory changes, or changes to the insurance program. The LAMP is currently being prepared for use in pilot analyses in communities around the country.
The proposed procedure is characterized by FEMA as being
a cost-effective, repeatable, and flexible approach that (1) complies with all statutory and regulatory requirements governing the NFIP, most notably 44 CFR §65.10, (2) leverages local input, knowledge, and data through proactive stakeholder engagement; (3) aligns available resources for engineering analysis and mapping commensurate with the level of risk in the leveed area; and (4) considers the unique flooding and levee characteristic (solely from an engineering perspective) of each levee system. (FEMA, 2011a)
Under the existing approach, when a levee is no longer accredited, all land areas that would be subject to inundation by the one percent annual chance flood if the levee system was not present are designated as SFHAs. Under the proposed approach, based on analyses of levee reaches,1 some lands areas may be determined to be still protected against inundation by the one percent annual chance flood. These land areas would be designated as Zone D, an existing designation that indicates undetermined, but possible flood hazard (Appendix E). Zone D areas are not subject to mandatory flood insurance purchase requirements, although structures in this zone may be subject to lenders’ flood insurance requirements. Rates under the NFIP would be adjusted from the preferred rate to a rate that reflects the undetermined risk for structures in Zone D.
The proposed approach makes use of five “procedures.” The Freeboard Deficient Procedure, Overtopping Procedure, and Structural-Based Inundation Procedure deal with common deficiencies in nonaccredited levee systems as they affect specific reaches. The Sound Reach Procedure deals with continuous reaches that were “designed, constructed, and maintained to withstand and reduce the flood hazards posed by a 1-percent-annual-chance flood” (FEMA, 2011a). The Natural Valley Procedure is applied to entire levee systems and assumes that “the levee system would not obstruct the river from flowing within the entire natural valley of the floodplain during the 1-percent-annual-chance flood event” (FEMA, 2011a).
The Freeboard Deficient Procedure is applied to levee reaches for which the only deficiency is inadequate freeboard. In this case, the Natural Valley Approach would be used to map the affected area. This area would be designated as Zone D, except for any portions that are affected by levee reaches with other deficiencies or are subject to flooding due to interior drainage.
The Overtopping Procedure is to be applied to levee reaches for which the one percent annual chance flood is higher than the crest, but overtopping will not result in structural failure. In this procedure the levee is modeled as a lateral weir, using a one percent annual chance flood plus a factor of safety. The inundated area is designated as an SFHA, and could be smaller than the inundated area that would result without consideration of the levee, as determined by the Natural Valley Procedure. If so, the remaining area is designated as Zone D, except for any portions subject to flooding due to internal drainage.
The Structural-Based Inundation Procedure is applied to levee systems that are not accredited because of structural integrity issues, such as insufficient foundation strength or vulnerability to seepage failure. In this procedure, possible failure locations are identified and evaluated to determine the inundated area. The modeling will be based on the one percent annual chance flood, without a factor of safety. Breaches will be assumed to occur at multiple locations. The inundated area will be designated as SFHA. This area could be smaller than the inundated area that would result without consideration of the levee, as determined by the Natural Valley Procedure. If so, the remaining area is designated as Zone D, except for any portions subject to flooding due to interior drainage.
The Sound Reach Procedure is applied to continuous sections of levee that have been designed, constructed, and maintained to withstand and reduce the flood hazards posed by a one percent annual chance flood. The areas landward of these levees are mapped using the Natural Valley Analysis and designated as Zone D, except where there is inundation due to internal drainage or to flows from the nonaccredited levee reaches.
LAMP also includes a stakeholder engagement process. Once FEMA has determined that a levee system does not meet the certification requirements, it will engage stakeholders to assist in the data collection phase. When appropriate, it will establish a Local Levee Working Group to provide additional data as well as feedback on the analysis and mapping. Depending on the nature of levee deficiencies, this data collection may involve considerable responsibility on the part of the local sponsors for technical data development, the costs of which may place a significant burden on their resources.
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1 A levee reach is a portion of a levee system (usually a length of a levee) that may be considered as a unit taken for analytical purposes to have approximately uniform representative properties. A levee reach will be the unique entity having properties different than other reaches of the levee system that may be used to evaluate the performance of a portion of the levee system. No maximum length is associated with a reach (USACE, 2010).
As part of the development of the LAMP, FEMA solicited input on a preliminary version of the procedure and received over 1,400 comments. The main criticisms of the proposed method had to do with the identification of a Zone D and the probability that the insurance rates in Zone D would rise and thus discourage insurance purchase. Suggestions were made to use the Zone X designation which carries less of a negative connotation.2
Technical comments addressed such issues as the failure of the Natural Valley method to account for local backwater effects caused by flow impediments such as levee tiebacks, confusion over the definition of a reach, use of the Freeboard Deficient Procedure believing that it “would remove elevation and insurance requirements behind a levee that has only one inch of freeboard and no armoring,” and failure in the Overtopping Procedure “to consider that the true one percent chance flood stage may be substantially higher than the median one percent stage,” suggesting that the Overtopping Procedure be replaced by the Structural-Based Procedure which does not appear to use a factor of safety. Fears were expressed that the new approach might “mislead the public and mortgage lenders about their risk, result in more risky development and fewer insurance policies, and dis-incentivize levee investments.” Other comments noted that Zone D lacks elevation data that could be useful to homeowners, builders, mortgage lenders, and communities.
The committee examined LAMP, met with key FEMA staff to discuss its possible implementation, and reviewed its components. The LAMP is founded on sound algorithms with sound science and engineering behind them and follows established approaches to hydrology and hydraulics. It is a first cut at an approach to dealing with the hazards associated with levees that do not meet the standards for protection against the one percent annual chance flood.
LAMP represents a response to the issues raised by members of Congress that, given funding and personnel constraints, it will likely take several years to fully implement. It represents a diversion of NFIP effort away from the long-recognized need to move the NFIP to risk-based analysis. Because it would be highly unlikely for the NFIP to move forward concurrently with implementation of LAMP and development of a modern risk-based approach as described in Chapter 3, a move to LAMP would simply postpone the inevitable need to move the NFIP to the risk-based foundation that other agencies and nations have already endorsed (Kobayashi and Porter, 2012; Serra-Llobet et al., 2013).
The implementation of LAMP would be a time-consuming and expensive endeavor for FEMA and communities.3 It will not yield the desired results of describing flood risks more accurately for the purposes of flood risk communication, mitigation, and insurance rate setting compared with a modern risk analysis. The LAMP approach does not identify or evaluate the properties at risk or the potential for losses and it does not consider levels of risk. In addition, it is not clear that the timescale for implementation of LAMP would contribute to resolving the flood mapping issues that currently exist.
Should the decision be made to implement LAMP, the implementation will not be simple or without controversy. It will require time for FEMA and communities to assess its viability and to establish the steps required for its systematic implementation. The steps in this process will necessarily involve
1. conducting a series of trial applications of LAMP at a number of locations to understand its impact, benefits, and the considerations in its broader implementation;
2. development of guidance for implementation of LAMP on a national scale, which might have a number of elements such as preparation of lessons from the trial applications, development of guidelines, preparation of training materials, Frequently Asked Question documents, holding of training seminars, etc.; and
3. implementation of a finalized LAMP across the nation, which may require
a. new hydraulic and hydrologic evaluations for levee reaches under evaluation,
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2 Zone X designates an area of moderate to low risk (see Appendix F).
3 Although no cost estimates were available for the implementation of LAMP, this statement is based on the judgment of the committee.
b. significant time and resource commitments by local communities and experts to develop local knowledge and data, and
c. resource-intensive FEMA review and evaluation of community submittals (acceptance or rejection).
It is not apparent to the committee how FEMA can reasonably and defensibly price flood insurance for the range of circumstances it will encounter with the LAMP approach. Criticisms that have been levied against the NFIP concerning high premiums may persist with such an implementation of LAMP. The implementation of LAMP and the concurrent actions that are required by the Biggert-Waters Flood Insurance Reform and Modernization Act of 2012 would likely lead to confusion among communities (e.g., the repackaging of Zone D) and will have a negative impact with respect to public engagement, risk communication, and NFIP viability and public acceptance of the program. FEMA should move directly to a modern risk-based analysis for dealing with areas behind levees and not implement the Levee Analysis and Mapping Procedure.
DEALING WITH THE CURRENT SITUATION
If LAMP is not implemented, what should FEMA do until a modern risk-based approach can be fully implemented? NFIP-related levees fall into four categories. The first group includes levees that are currently fully accredited. A second group encompasses deaccredited levees with deficiencies that the community intends to remediate in order to bring the levee back into compliance with the provisions of 44 CFR §65.10. Depending on the nature of the deficiency and the costs associated with remediation, such actions may take a few to several years. The third group of levees includes those with deficiencies that the community recognizes cannot reasonably be remediated and that the community does not intend to remediate. This situation develops when the levee deficiencies are severe or the potential costs for repair or upgrade are so substantial that it would be impossible for the community to bear such costs. The fourth group of levees includes those that are not now accredited or that are proposed to be built at less than 44 CFR §65.10 standards to provide some level of protection to those behind levees against more frequent than one percent annual chance floods (e.g., 2 percent annual chance or 50-year floods).
Should a decision be made not to implement LAMP and to develop and a modern risk-based analysis, dealing with the current situation is still necessary. Pending development and completion of a modern risk-based analysis, FEMA should implement and promote these interim steps:
1. Communities with currently certified levees not in the mapping process and not having been declared deaccredited would be expected to take necessary actions to remediate any deficiencies that have been brought to their attention as a result of USACE or FEMA programs so that when the community is remapped, the levee would meet standards.
2. If the community indicates that it will take steps to restore accreditation, the following action would be taken with respect to its levees:
a. Communities would commit to an aggressive but reasonable program to remediate all deficiencies in the levees using a program similar to the USACE System-Wide Improvement Framework (SWIF) policy (Appendix I) or an integration of the SWIF and an NFIP remediation program. The SWIF policy requires participating levee sponsors to
i. provide a “description of deficiencies or issues that will be included in the SWIF and discussion of how a system-wide approach will improve and optimize overall flood risk reduction";
ii. demonstrate “that significant nonfederal resources have been, or will be, committed for developing and/or implementing the SWIF (e.g., state legislative action, bond financing)";
iii. identify “risk reduction measures that will be implemented throughout the SWIF process, including [an] overall risk communication approach that addresses [how] the risk to life increased by system-wide deficiencies” is being mitigated during the remediation period”; and
iv. describe “existing or planned interagency collaborative efforts that will contribute positively to SWIF development, implementation and oversight” (USACE, 2011).
b. Issuance of preliminary maps would be suspended until remedial action was completed. These levees would be left in the current program and any actions to remove them from accreditation would be suspended temporarily. Areas behind levees would remain outside of the SFHA and would be considered in Zone X.
c. To ensure the protection of the health, welfare, and property of those in the leveed areas, communities would be required to carry out the following actions:
i. individually inform all residents living behind the subject levees of the failure of the levee to meet FEMA and/or USACE standards, the nature of the deficiencies, resultant risks that exist, and steps being taken by the community to remediate the deficiencies;
ii. review and exercise emergency plans to include plans for the evacuation of residents from behind the levees; and
iii. encourage those behind levees to purchase insurance policies.
3. If communities do not intend to seek reaccreditation of deaccredited levees:
a. Mapping efforts would continue through issuance of the effective maps indicating that areas behind the levees are in the SFHA and subject to mandatory purchase requirements and land development regulations. At the time the new maps go into effect, the rate charged would be that for the SFHA.
b. After FEMA completes the development of a new risk-based analysis approach, the rates for these areas would be reassessed to reflect the degree of risk reduction provided by the less-than-compliant levees.
c. To ensure the protection of the health, welfare, and property of those in the leveed areas, communities would be required to carry out the following actions:
i. individually inform all residents living behind the subject levees of the failure of the levee to meet FEMA and/or USACE standards, the nature of the deficiencies, resultant risks that exist and the intention of the community to not remediate the deficiencies;
ii. review and exercise emergency plans to include plans for the evacuation of residents from behind the levees;
iii. encourage the purchase by those behind levees of insurance policies at the preferred risk rate;
iv. provide FEMA with reports of locally funded periodic inspections of the assessed levees to ensure that they continue to maintain the degree of protection used in the risk analysis.
4. Communities wishing to build a new levee in an existing SFHA or in an area where there is no flood designation should be required to construct the new levees to NFIP standards. Where a participating community has within its geographic bounds and within the SFHA levees that do not currently meet NFIP standards and that have never been proposed for certification, it would be possible, on completion of the development of risk-based analysis, for these communities to request, at community expense, FEMA evaluation of the levees to determine risk-based SFHA insurance pricing for properties affected by these levees.
Levees were introduced into the NFIP because, at the time, decision makers reasoned that because new construction within the SFHA would be required to be at or above one percent annual chance flood level in order to be removed from the mandatory purchase requirement, equity dictated that those protected by a one percent annual chance “flood control” structure should also be removed from the requirements of mandatory insurance and land management behind the structures. It was assumed that these structures would provide protection equal to or in excess of the protection provided by requiring the first flood of new development in the SFHA to be at or above the one percent annual chance flood level. As indicated in Chapter 2, because the decision that areas behind levees are not subject to the mandatory purchase requirement and land regulation, studies and internal deliberations between USACE and FEMA since the early 1970s have highlighted that the aggregate risk to those behind levees may be greater than the risk to those in front of the levees (FEMA, 2006; Galloway et al., 2006; NFIP Evaluation Final Report Working Group, 2006; ASFPM, 2007; CA DWR, 2007).
ASFPM (Association of State Floodplain Managers). 2007. National Flood Policy Challenges Levees: The Double-Edged Sword. Madison, WI: ASFPM.
CA DWR (California Department of Water Resources). 2007. A California Challenge: Flooding in the Central Valley. Sacramento, CA: Department of Water Resources.
FEMA (Federal Emergency Management Agency). 2006. The National Levee Challenge: Levees and the FEMA Flood Map Modernization Initiative. Washington, DC: FEMA.
FEMA. 2011a. Analysis and Mapping Procedures for Non-Accredited Levees. Proposed Approach for Public Review. Available online at http://www.fema.gov/library/viewRecord.do?id=4954. Accessed November 28, 2012.
FEMA. 2011b. National Flood Insurance Program: Answers to Questions About the NFIP. FEMA F-084. Available online at http://www.fema.gov/library/viewRecord.do?fromSearch=fromsearch&id=1404. Accessed February 15, 2013.
Galloway, G. E., G. B. Baecher, D. Plasencia, K. G. Coulton, J. Louthain, M. Bagha, and A. R. Levy. 2006. Assessing the Adequacy of the National Flood Insurance Program’s 1 Percent Flood Standard. Washington, DC: American Institutes for Research. Available online at http://www.fema.gov/library/viewRecord.do?id=2595.
Kobayashi, K., and J. W. Porter. 2012. Flood Risk Management in the Peoples Republic of China: Learning to Live with Flood Risk. Mandaluyon City, Philippines: Asian Development Bank.
NFIP Evaluation Final Report Working Group. 2006. The Evaluation of the National Flood Insurance Program: Final Report. Washington, DC: American Institutes for Research.
Serra-Llobet, A., J. D. Tàbara, and D. Sauri. 2013. The Tous Dam disaster of 1982 and the origins of integrated flood risk management in Spain. Natural Hazards 65: 1981-1998.
USACE (U.S. Army Corps of Engineers). 2010. USACE Process for the National Flood Insurance Program (NFIP) Levee System Evaluation. Available online at http://publications.usace.army.mil/publications/eng-circulars/EC_1110-2-6067.pdf. Accessed November 27, 2012.
USACE. 2011. Memorandum for Commanders, Major Subordinate Commands, and Districts—Policy for Development and Implementation of System-Wide Improvement Frameworks (SWIFs). Washington, DC: USACE.
