Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
A LEVEE POLICY FOR THE NATIONAL FLOOD INSURANCE PROGRAM A Committee on a Levee Policy for the National Flood Insurance Program .», Water Technologies Board Commission on Engineering and Technical Systems National Research Council OCT * 0 1982 NATIONAL ACADEMY PRESS Washington, D.C. 1982 J iftRARY
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors, according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and of advising the federal government. The Council operates in accordance with general policies determined by the Academy under the authority of its congressional charter of 1863, which establishes the Academy as a private, nonprofit, self-governing membership corporation. The Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in the conduct of their services to the government, the public, and the scientific and engineering communities. It is administered jointly by both Academies and the Institute of Medicine. The National Academy of Engineering and the Institute of Medicine were established in 1964 and 1970, respectively, under the charter of the National Academy of Sciences. This report represents work supported by Contract Number EMW-C-0606 between the Federal Emergency Management Agency and the National Academy of Sciences
COMMITTEE ON A LEVEE POLICY FOR THE NATIONAL FLOOD INSURANCE PROGRAM Members L. Douglas James, Chairman Utah State University Logan, Utah Leo M. Eisel Wright Water Engineering Denver, Colorado Gerald E. Galloway U.S. Military Academy West Point, New York Carl W. Kreitzberg Drexel University Philadelphia, Pennsylvania Rutherford H. Platt University of Massachusetts Amherst, Massachusetts Henry Reitz Reitz & Jens, Inc. St. Louis, Missouri Robert L. Smith University of Kansas Lawrence, Kansas W. D. Swift Swift Insurance Service Company Little Silver, New Jersey L. Scott Tucker Urban Drainage and Flood Control District Denver, Colorado Frederick A. Webster Jack R. Benjamin and Associates, Inc. Mountain View, California French Wetmore Illinois Department of Transportation Chicago, Illinois Eric F. Wood Princeton University Princeton, New Jersey Liaison Representatives Lloyd A. Duscha U.S. Army Corps of Engineers Earl Jones Department of Housing and Urban Development Walter Ochs USDA Soil Conservation Service Frank H. Thomas U.S. Water Resources Council Technical Consultant George W. Brazier, Jr. Consulting Civil Engineer Luray, Virginia 111
Workshop Participants Gregory Baecher Massachusetts Institute of Technology Cambridge, Massachusetts Duane Baumann Southern Illinois University Carbondale, Illinois Richard Buncie U.S. Army Corps of Engineers St. Louis, Missouri Joel Crawford Scott Company Hilton Head, South Carolina Lucien Duckstein University of Arizona Tucson, Arizona Gary Dyehouse U.S. Army Corps of Engineers St. Louis, Missouri Burrell Fair Saint Francis Levee Board of Arkansas West Memphis, Arkansas John Graham Susquahanna River Basin Commission Harrisburg, Pennsylvania R. G. Kazman Louisiana State University Baton Rouge, Louisiana John Koeper Metro St. Louis Sewer District St. Louis, Missouri Richard L. Konsella New York State Department of Conservation Albany, New York Paul Lanferman Alameda County Flood Control and Water Conservation District Hayward, California Guy F. LeMieux J. J. Krebs & Sons Metairie, Louisiana James Lewin New Orleans East Incorp. New Orleans, Louisiana Earle Magner Orleans Levee Board New Orleans, Louisiana William Remmert U.S. Army Corps of Engineers St. Louis, Missouri Everett W. Rowland Texas Department of Water Resources Austin, Texas Harold Vance Los Angeles County Flood Control District Los Angeles, California Robert Watson Department of Natural Resources Madison, Wisconsin Dennis J. Welker Booker Associates St. Louis, Missouri Agency Representative Brian R. Mrazik Federal Emergency Management Agency IV
WATER TECHNOLOGIES BOARD Members Walter R. Lynn (Chairman) Cornell University Ithaca, New York Leo R. Beard Consulting Engineer Austin, Texas John J. Boland Johns Hopkins University Baltimore, Maryland Richard S. Engelbrecht University of Illinois at Urbana - Champaign Urbana, Illinois Jerome B. Gilbert East Bay Municipal Utility District Oakland, California Yacov Y. Haimes Case Western Reserve University Cleveland, Ohio L. Douglas James Utah State University Logan, Utah Robert B. Jansen Consulting Engineer Mead, Washington John F. Kennedy The University of Iowa Iowa City, Iowa David W. Miller Geraghty & Miller, Inc. Syosset, New York Stephen E. Reynolds State Engineer of New Mexico Santa Fe, New Mexico Daniel P. Sheer Interstate Commission on the Potomac River Basin Rockville, Maryland Robert L. Smith University of Kansas Lawrence, Kansas Staff Stephen D. Parker Executive Director Sheila D. David Staff Officer Jeanne Aquilino Administrative Secretary Carole B. Carstater Administrative Secretary
PREFACE Levees provide a viable structural approach for reducing average annual flood damages, but it is an approach that should be used with care. Levee tops that are higher than flood crests bar movement of flood waters onto lands behind them, but levees must be carefully engineered and maintained so as not to fail structurally during events too small for their overtopping. Furthermore, levees often lead to more intense land development behind them and are subject to sudden failures that can add to damage totals during extreme events. It is because levees reduce average annual flood damages that FEMA is being pressured to reduce flood insurance premiums for buildings behind levees, the logic being that protected property owners should not both pay for the levee and then be required to pay insurance premiums based on full damage exposure. It is because of the need for care in using levees that FEMA has an obligation to recognize only levees that are properly engineered and structurally sound. Riverine levees extend for thousands of miles along water courses from the nation's largest rivers to some very small streams, making levee inventory, inspection, evaluation, and acceptance or rejection a formidable process. The committee reviewed technical considerations for application in evaluating the great number of existing and proposed levees for hydraulic and geotechnical soundness. This document formulates principles for a levee policy that will provide equity for protected parties in terms of recognition for efforts spent in reducing their risk without encumbering program administration with an unwieldy number of variations in levels of recognition of levee efficacy. The details will need to be developed from these principles by FEMA. The committee defined six dimensions of levee recognition. The design protection level appropriate for recognition depends on whether the application is for 1) reduction in insurance rates, 2) easing land occupancy regulations, 3) eliminating flood insurance purchase requirements, 4) permitting siting of critical facilities, 5) removing requirements for notifying occupants of the hazard, or 6) eliminating warning and evacuation programs. Each recommended levee recognition distinction was based on the experience and judgment of the committee members integrating technical considerations with economic and vi
administrative factors. Each recommendation is re-isoneU and presented in the body of the report, and all of them are listed for convenience in a final summary chapter. Table 1 in Chapter 2 condenses the levee-recognition policy recommendations and mapping suggestions on one page. Appendix A defines technical terms used in the context of the report. As when any group of people assemble to discuss a complex and controversial issue, differences of opinion arose. A few of the 35 recommendations made by this committee were not unanimous, and the cases made by committee members with contrary viewpoints are given in Appendix D to complete the record. As this report is advisory, the complete record provides the Federal Emergency Management Agency more information for weighing in formulating policy. The discussion coalescing in these minority opinions caused the committee to give these issues particular attention throughout the study and review processes. Consequently, speaking as an author of one of them, a lack of unanimity should be taken as an indication that there is legitimate room for debate, and the choice of the majority suggests that the balence of existing evidence supports the positions articulated in the committee recommendations. In the opinion of the chairman, the focus of the committee recommendations is on recognition of levees along rivers where flows, depths, and velocities are large enough to pose threat to life. In small watersheds, levees are often used to augment channel capacity or provide freeboard at locations where channels, flows, and flood volumes are small. FEMA should not automatically extrapolate committee procedural recommendations (such as those on design, maintenance, and evacuation plan detail) to smaller streams without being able to justify reasonableness in terms of maintaining, but not exceeding, the level of protection presented in principle in the body of this report. The consideration of reasonableness is particularly important in setting program priorities. The chairmanship of this committee has been an interesting and enriching experience. The committee members, agency liaisons, and workshop participants gave willingly of their time and counsel and deserve credit for the substance and recommendations found in this report. The committee is grateful to the staffs of the National Research Council and the Federal Emergency Management Agency for support that enabled the committee to focus quickly and efficiently on the assigned task and to complete it on time. L. Douglas James October 12, 1982 Chairman VI1
CONTENTS 1. INTRODUCTION 1 Background 1 National Research Council Approach and Objectives 3 Interim FEMA Policy on Levees 4 2. COMMITTEE APPROACH TO LEVEE POLICY 5 Dimensions of Levee Recognition 5 Recognition by Program Dimension 7 Technical Guidance for Setting Levee Policy ....7 3. ENGINEERING CRITERIA FOR LEVEE RECOGNITION 10 General 10 Recognition of Levees in the National Flood Insurance Program 11 Structural Criteria 13 Other Factors to be Considered 16 Exceptions 17 4. LEVEE INSPECTION AND EVALUATION 18 Considerations and Relationship to Design Criteria 18 Inspection and Evaluation Procedures for New Levees... 19 Inspection and Evaluation Procedures for Existing Levees 19 Operation and Maintenance Evaluation 23 5. REQUIREMENTS OF LEVEE OWNERS 24 Genera 1 24 Operation and Maintenance Goals..... 24 Recommended Operation and Maintenance Guidelines 25 Operation and Maintenance Inspection 26 6. REQUIREMENTS OF LOCAL COMMUNITIES 28 Floodplain Regulations 28 Flood Insurance Purchase 29 Critical Facilities 31 Notice to Residents 31 Adoption of a Predisaster Warning and Evacuation Plan.. 32 7. LIABILITY OF LOCAL GOVERNMENTS AND LEVEE DISTRICTS CONCERNING LEVEE MAINTENANCE AND FLOODPLAIN MANAGEMENT 33 Discussion 33 Conclusion 38 IX
8. TREATMENT OF LEVEES IN THE INSURANCE ASPECTS OF THE NFIP 39 Discussion and Recommended Approach 39 Hazard Rating Procedure 41 9. FLOODPLAIN MAPPING APPROACHES IN LEVEE-PROTECTED AREAS 47 Purpose and Discussion 47 Flood Insurance Maps Prepared by FEMA 48 Mapping for Credited Levees Providing 100-Year Protection 49 Mapping for Credited Existing Levees Not Providing 100-Year Flood Protection 60 Evacuation Routes 63 Interior Drainage 63 X. SUMMARY OF RECOMMENDATIONS.. 65 APPENDIXES A GLOSSARY 75 B FEMA INTERIM POLICY ON LEVEES 80 C GUIDELINES FOR OPERATION AND MAINTENANCE OF LEVEE, FLOODWALL, AND INTERIOR DRAINAGE FACILITIES 89 D MINORITY OPINIONS 96 E BIOGRAPHICAL SKETCHES OF LEVEE COMMITTEE MEMBERS 102 F BIBLIOGRAPHY.......... 106
LIST OF TABLES Number Title Page 1 Dimensions of Levee RecognitionâSummary 8 2 Example Levee Rating Procedure 45 3 Rating Check List: An Example 46 XI
