Attachment N - FEMA Guidanance for Flood Risk Analyis.pdf

Guidance for Flood Risk Analysis and Mapping

Levees

November 2019

Attachment N FEMA Guidance for Flood Risk

Levees November 2019 Guidance Document 95 Page i

Requirements for the Federal Emergency Management Agency (FEMA) Risk Mapping, Assessment, and Planning (Risk MAP) Program are specified separately by statute, regulation, or FEMA policy (primarily the Standards for Flood Risk Analysis and Mapping). This document provides guidance to support the requirements and recommends approaches for effective and efficient implementation. The guidance, context, and other information in this document is not required unless it is codified separately in the aforementioned statute, regulation, or policy.

Alternate approaches that comply with all requirements are acceptable.

For more information, please visit the FEMA Guidelines and Standards for Flood Risk Analysis and Mapping webpage (www.fema.gov/guidelines-and-standards-flood-risk-analysis-and-mapping), which presents the policy, related guidance, technical references, and other information about the guidelines and standards development process.

http://www.fema.gov/guidelines-and-standards-flood-risk-analysis-and-mapping http://www.fema.gov/guidelines-and-standards-flood-risk-analysis-and-mapping

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Table of Revisions The following summary of changes details revisions to this document subsequent to its most recent version in February 2019.

Affected Section or Subsection Date Description

Section 1 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 2 November

Corrected minor typos and alignment of wording.

Removed list of acronyms.

Section 3 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 4 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 5 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 6 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 7 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Section 8 and all subsections

November 2019 Corrected minor typos and alignment of wording.

Guidance Document 95 Page iii

Table of Contents

1.0 Levees Overview

1.1 Prior Guidance Documents

1.2 Flood Hazard Mapping and Levees

1.3 Summary of Recent Legislation and Recommendations

1.4 Levee-Related Communication and Community Engagement

1.5 Chapter Overviews

2.0 Glossary

3.0 Levee Data Inventory

3.1 Background

3.2 National Levee Database

3.3 Identification and Mapping of Levees in Flood Hazard Studies and Map Revisions

3.4 FEMA Regulatory Levee Data

3.5 Tracking Levee Accreditation Status

3.6 Reporting Levee System Updates

3.7 Levee Data Storage Standards

4.0 Accredited Levee Systems

4.1 44 CFR 65.10 Requirements

4.2 Additional Levee Accreditation Considerations

4.3 Levee Accreditation Reviews

4.4 Accredited Levee Mapping and Notes

5.0 Provisionally Accredited Levee Systems

5.1 Provisional Levee Accreditation Overview

5.2 PAL Eligibility Requirements

5.3 Considerations for Offering PAL to PAL Eligible Levee Systems

5.4 PAL Communication and Coordination Processes

5.5 PAL Mapping and Notes

6.0 Non-Accredited Levee Systems

6.1 Non-Accredited Levee Systems Defined

6.2 Other Considerations

6.3 Levee Analysis and Mapping Procedure

6.4 Levee Data Collection and Stakeholder Engagement (Figure 11, Element 200)

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6.5 Local Levee Partnership Team (Figure 11, Element 300)

6.6 Local Levee Partnership Team Meetings (Figure 11, Element 300)

6.7 Levee Analysis and Mapping Plan (Figure 11, Element 400)

6.8 Additional Data Collection (Figure 11, Element 410)

6.9 System-Wide Analysis and Mapping Procedures (Figure 11, Element 610)

6.10 Interior Drainage Analysis

6.11 Levee Reach Analysis and Mapping Procedures (Figure 11, Element 620)

6.12 Natural Valley Procedure (Figure 11, Element 620)

6.13 Structural-Based Inundation Procedure (Figure 11, Element 620)

6.14 Overtopping Procedure (Figure 11, Element 620)

6.15 Freeboard Deficient Procedures (Figure 11, Element 620)

6.16 Sound Reach Procedure (Figure 11, Element 620)

6.17 Flood Hazards Evaluated by Flooding Source (Figure 11, Element 630)

6.18 Hydrograph Development

6.19 Regulatory Floodways

6.20 Hydraulic Modeling on Landside of the Levee

6.21 Flood Hazard Mapping

6.22 Guidance Regarding Flood Insurance Study Report Standards

6.23 Documentation

6.24 Review Procedures

7.0 Non-Levee Reaches and Non-Levee Features

7.1 Non-Levee Reach

7.2 Non-Levee Features

7.3 Communication of Risk

8.0 FEMA and Other Federal Agency Coordination

8.1 USACE

List of Figures Figure 1: Example Levee System A

Figure 2: Freeboard Determination

Figure 3: Freeboard Near Structures

Figure 4: Wave Runup

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Figure 5: Levee System Designed to End in the Absence of High Ground

Figure 6: Levee System Tying into Non-Levee Reach

Figure 7: Non-Accredited Levee System

Figure 8: Multiple-Levee Scenario

Figure 9: PAL Determination Decisions Tree

Figure 10: Initial Notification Letter within Risk MAP Project Timeline

Figure 11: FEMA Levee Analysis and Mapping Procedure

Figure 12: Levee Data Collection and Stakeholder Engagement Process

Figure 13: Sample of Potential Inundation Extents

Figure 14: Example Segmentation of a Levee System

Figure 15: Natural Valley Cross-Section View

Figure 16: SFHA Delineation Using Natural Valley Procedure

Figure 17: Structural-Based Inundation Cross-Section View

Figure 18: SFHA Delineation Using Structural-Based Inundation Procedure

Figure 19: Overtopping Cross-Section View

Figure 20: SFHA Delineation Using Overtopping Procedure

Figure 21: Freeboard Deficient Cross-Section View

Figure 22: Sound Reach Cross-Section View

Figure 23: Sample Dimensionless Unit Hydrograph

Figure 24: Floodway Analysis Process Initial Analysis

Figure 25: Floodway Analysis Process Initial Analysis

Figure 26: Final Regulatory Floodway

Figure 27: Both Encroachments (A and B) on Riverside of Levees

Figure 28: One Encroachment on Riverside of Levee (A) and the Other on Landside of Levee (B)

Figure 29: The Landside Encroachment (B) Moved to the Levee

Figure 30: Both Encroachments at Levees

Figure 31: Both Encroachments Landward of the Levees

Figure 32: Use of Natural Valley Procedure to Determine Initial Encroachment Stations A and B

Figure 33: Using Left levee holding to find encroachment station C

Figure 34: Right Levee Holding to Find Encroachment Station D

Figure 35: Both levees Are Non-accredited

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Figure 36: Left Levee Is Non-accredited, Right Levee Is Accredited

Figure 37: Right Levee Is Non-accredited, Left levee Is Accredited

Figure 38: Composite Mapping of Flood Hazards for the Levee System

Figure 39: Non-Levee Reach

Figure 40: Non-Levee Feature

List of Tables Table 1: Levee Terms

Table 2: Summary of Minimum PAL Requirements

Table 3: Suggested Timeline for Additional Data

Table 4: Summary of Stakeholder Data Requirements for Reach Analysis Procedures

Table 5: Sample Summary of Hydrologic and Hydraulic Analyses Table Guidance Clarification Routing

Table 6: Crop Insurance, Flood Insurance Rate Maps, and Levees

Guidance Document 95 Page 1

1.0 Levees Overview

This consolidated guidance document was prepared for FEMA, as part of the Risk MAP program, to promote sound and consistent implementation of levee-related National Flood Insurance Program (NFIP) regulations and mapping program standards that apply to levees.

This guidance document is intended to provide current information on the mapping of levees and associated flood hazards. This document captures current standards and practices and, therefore, does not address all topics related to the identification of flood hazards and risks associated with levees.

Federal, State, and local officials have often considered levee systems an effective structural approach for reducing average annual flood losses. However, it is an approach that needs to be considered cautiously. Carefully engineered and well-maintained levees should divert floodflows as intended in their design and keep the areas landward of the levees dry if their structural integrity is not compromised, all elements of the system are functional, and the floodwaters do not overtop the structure. However, a primary drawback is that levees could lead to increased development of areas landward of the levees over time and thereby increase the exposure to catastrophic failures during extreme events (A Levee Policy for the National Flood Insurance Program, National Academy Press, 1982).

When it comes to working with communities on levee-related mapping projects or issues, FEMA shares a mission with its State agency partners, the U.S. Army Corps of Engineers (USACE), and other Federal agencies. That mission entails helping levee owners, flood control districts, community officials, floodplain managers, the media, and other stakeholders understand and properly communicate the risks associated with living and working landward of levees. Living with levees is a shared responsibility and local community officials should remain engaged in flood risk management activities. It is important for all stakeholders to know the risk; their role in helping to reduce that risk; and what specific actions they can take, including the purchase of flood insurance to further reduce the financial risk associated with living and working in levee-impacted areas. For more information, visit the Living with Levees: It’s a Shared Responsibility portion of the FEMA website (www.fema.gov/living-levees-its-shared-responsibility).

The primary audiences for this guidance document are communities, regional entities, Tribal entities, and State agencies, including those participating in the Cooperating Technical Partners program (CTPs), FEMA Project Teams that are formed to carry out projects in support of the FEMA Regional Offices, and FEMA Regional Office and Headquarters staff. The FEMA Project Teams often include representatives of the FEMA Risk MAP providers. This guidance document is also intended for communities and local stakeholders involved in levee accreditation and the implementation of FEMA non-accredited levee analysis and mapping procedures.

The levee guidance in this document emphasizes the Risk MAP program vision of collaborating with local, regional, State, and Tribal entities throughout a watershed to deliver quality data that increases public awareness and leads to mitigation actions that reduce flood risk to life and property. To achieve this vision, FEMA transformed its historic documents for flood hazard http://www.fema.gov/living-levees-its-shared-responsibility

Guidance Document 95 Page 2 identification and mapping efforts into a more integrated process of identifying, assessing, communicating, planning, and mitigating flood-related risks aligned with the Risk MAP vision1.

To accomplish this process, the appropriate analyses, mapping, and communication of risk of levee systems is necessary throughout the Risk MAP project lifecycle. FEMA has prepared this consolidated guidance in keeping with that responsibility.

1.1 Prior Guidance Documents

The consolidation of work that guided users through decades of levee-related procedures implemented during flood hazard mapping projects were incorporated into this guidance document. This is intended to promote sound and consistent implementation of policies, regulations, and standards for levee risk evaluation. This guidance enhances compliance with the Code of Federal Regulations; incorporates portions of Analysis and Mapping Procedures for Non- Accredited Levee Systems New Approach, (July 2013); and FEMA standards to facilitate implementation during flood hazard mapping projects. This guidance document has been prepared to expand on, and supersede, guidance provided in FEMA Operating Guidance (OG) 12-13; Procedure Memorandum (PM) Nos. 34, 43, 45, 51, 52, 53, and 63; and Appendix H of Guidelines and Specifications for Flood Hazard Mapping Partners. More details for each superseded guidance document are provided in each chapter of this document.

This guidance document does not supersede the following existing FEMA guidance documents:

• Analysis and Mapping Procedures for Non-Accredited Levee Systems New Approach, dated July 2013.

• Guidance Document No. 29, Guidance for Flood Risk Analysis and Mapping: Levee Seclusion, dated November 2014.

• Guidance Document No. 34, Guidance for Flood Risk Analysis and Mapping: Zone A99 and Zone AR Determinations, dated May 2015.

• Guidance Document No. 72, Guidance for Flood Risk Analysis and Mapping: Levee- Specific Non-Regulatory Flood Risk Datasets, dated May 2016.

These and additional mapping guidance and best practices can be accessed through the FEMA Guidelines and Standards for Flood Risk Analysis and Mapping webpage.

1.2 Flood Hazard Mapping and Levees

FEMA does not design, build, inspect, operate, maintain, or certify levees. However, as administrator of the NFIP, FEMA is responsible for accurately identifying flood hazards and communicating those hazards and risks to affected stakeholders.

Conditions in a community or watershed change over time; therefore, the need to update flood hazard information reflected on Flood Insurance Rate Maps (FIRMs) is assessed periodically to better reflect the current flood risk to people and property. FEMA updates FIRMs nationwide through the Risk MAP program. FEMA shows levee systems on the FIRM as being accredited, 1 For more information on the Risk MAP program, see https://www.fema.gov/risk-mapping-assessment-and-planning-risk-map.

https://www.fema.gov/risk-mapping-assessment-and-planning-risk-map

Guidance Document 95 Page 3 provisionally accredited, non-accredited, or in the process of being restored or constructed. FEMA designates the areas landward of the levees as Zone A, Zone AE, Zone AR, Zone A99, Zone D, Zone X (shaded), or Zone X depending on the status of the levee systems and the type of study performed. With new or updated FIRMs, community officials will have information to help them advise where and how to build more safely, and the public will understand their risk, allowing more informed decisions about reducing the risk to families, homes, and businesses.

Levees add complexity to an ongoing flood hazard study. To address the complexities that levees introduce, a FEMA Project Team should consider the presence of levees and appropriate mapping procedures as early in the study process as possible. Early consideration will help ensure that appropriate data collection and coordination occur. Subsections 1.2.1 through 1.2 5 briefly introduce the possible mapping options for levees.

1.2.1 Accredited Levee System

An accredited levee system is a system that FEMA has determined meets requirements of the NFIP regulations as cited in the Code of Federal Regulations (CFR) at Title 44, Chapter 1, Section

65.10 (44 CFR 65.10) and that FEMA has recognized on a FIRM as reducing the flood hazards posed by a base (1-percent-annual-chance) flood. This determination is based on a submittal, by or on behalf of a community, which includes 44 CFR 65.10–compliant design data and documentation, certified by a registered Professional Engineer (P.E.), and operations and maintenance documentation under the appropriate jurisdiction. FEMA strongly encourages flood insurance for all insurable structures in floodplains, including those in areas landward of levees.

FEMA accreditation of a levee system does not guarantee that the levee will provide flood hazard reduction to properties from flooding; therefore, FEMA has included a note on related FIRM panels that overtopping, or failure of an accredited levee system is possible. To mitigate flood risk in residual risk areas, property owners and residents are encouraged to consider flood insurance and floodproofing or other protective measures. Chapter 4 of this document provides detailed information on the mapping of accredited levee systems.

1.2.2 Provisionally Accredited Levee System

When the area impacted by an accredited levee system shown on an effective FIRM is in the process of being remapped, FEMA may ask the levee owner or community to provide data and documentation demonstrating the levee system still meets the requirements set forth in 44 CFR

65.10. To assist levee owners and communities, FEMA established the Provisionally Accredited Levee (PAL) designation as an option for mapping the area while providing levee owners or communities more time to gather the required data and documentation. The levee owner signs and submits an agreement to FEMA indicating the data and documentation required for compliance with 44 CFR 65.10 will be provided within 24 months of the 91st day following the date of the initial FEMA notification letter. FEMA places a note on the impacted FIRM panel(s) landward of the levee system to indicate FEMA has provisionally accredited the levee system and the designation of any existing Zone X (shaded) areas of flood hazard reduction due to levees is provisional. Chapter 5 of this document provides detailed information on the mapping of PALs.

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1.2.3 Non-Accredited Levee System

Non-accredited levee systems are levee systems that do not meet the NFIP regulatory requirements of 44 CFR 65.10 and that are not shown on a FIRM as reducing the base flood hazard. FEMA recognizes that non-accredited levee systems do impact flood risk; for that reason, FEMA has developed analysis and mapping procedures for non-accredited levees that provide a suite of approaches for analyzing flood hazards landward of levee systems. Chapter 6 of this document provides detailed information on the mapping of non-accredited levee systems.

1.2.4 Levees Undergoing Restoration (Zone AR) and Undergoing Construction (Zone A99)

The NFIP regulations contain two provisions that help ameliorate the flood insurance impact on property owners during the restoration of non-accredited levee systems or construction of new levee systems. These are based on provisions of the National Flood Insurance Act of 1968, as amended, as cited in the United States Code (U.S.C.) at 42 U.S.C. 4014 (e) and 42 U.S.C.

4014(f). These provisions are intended to provide reduced flood insurance premium rates for insurable structures landward of levee system projects designed and intended for eventual accreditation. Under these provisions, a levee system undergoing construction, or restoration, but that cannot currently meet 44 CFR 65.10 requirements, is recognized by FEMA as providing some (less than the base flood) level of hazard reduction.

FEMA issues Flood Protection Restoration determinations, regulated through 44 CFR 65.14, in areas where a project is sufficiently underway to restore a levee system to meet 44 CFR 65.10 accreditation requirements. FEMA maps the areas landward of the levee system that is being restored as Zone AR on the FIRM and may present Base Flood Elevations (BFEs) representing the current hazard as if the levee system was not in place. The Zone AR determination may provide property owners with reduced flood insurance premium rates lower than rates in other mapped Special Flood Hazard Areas (SFHAs).

FEMA issues adequate progress determinations, regulated through 44 CFR 61.12, in areas where FEMA determines that a community has made adequate progress on a levee system construction or reconstruction project designed for flood hazard reduction. FEMA maps the areas landward of the levee system as SFHAs designated Zone A99 on the FIRM. The Zone A99 determination also provides flood insurance premium rates and floodplain management requirements that are generally less than those required in other SFHAs. The Zone A99 designation is used in place of a shaded Zone X protected by levee designation for the landward area of the levee system. The horizontal extent of the Zone A99 would match the boundary extent of the potential area of reduced flood hazard that in the future would be adjusted to a shaded Zone X protected by levee designation.

Detailed information on Flood Protection Restoration and Adequate Progress determinations is provided in FEMA Guidance Document No. 34, Guidance for Flood Risk Analysis and Mapping:

Zone A99 and Zone AR Determinations. Guidance Document No. 34 is accessible through the FEMA Guidelines and Standards for Flood Risk Analysis and Mapping webpage.

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1.2.5 Levee Seclusion Mapping

In March 2011, FEMA committed to updating the way flood hazards for non-accredited levee systems were analyzed and mapped. As a result, some in-progress FIRM updates that included levee systems were delayed or otherwise impacted while FEMA developed the analysis and mapping approach for non-accredited levees. FEMA developed the levee seclusion mapping approach as a project management solution to allow the release of the FIRM updates for those portions of the community outside of the levee-impacted area. Through the levee seclusion mapping approach, FEMA maintains the flood hazard information as depicted on the current effective FIRM (the FIRM in effect before the in-progress update) with map notes explaining that the flood hazard information in these areas will be updated after FEMA applies an updated levee analysis and mapping approach. Levee seclusion was not intended to be a long-term mapping approach and was not anticipated to be implemented on any mapping projects initiated after July 2013. Detailed information on seclusion is provided in FEMA Guidance Document No. 29, Guidance for Flood Risk Analysis and Mapping: Levee Seclusion, which is accessible through the FEMA Guidelines and Standards for Flood Risk Analysis and Mapping webpage.

1.3 Summary of Recent Legislation and Recommendations

This section summarizes some recent legislation and recommendations related to managing and assessing levee systems.

1.3.1 Water Resources Development Act of 2007

Title IX of the Water Resources Development Act (WRDA) 2007, the National Levee Safety Act of 2007, as amended, includes activities incentivizing the creation of State and Tribal levee safety programs and increased public awareness of levee systems. Activities include, among other provisions, the development and maintenance of the National Levee Database (NLD); inventory and review levees;

development of levee guidelines; and development of technical assistance and training materials.

Recommendations leading up to this legislation can be found on the USACE website (www.usace.army.mil/National-Levee-Safety/).

1.3.2 Flood Protection Structure Accreditation Task Force

The USACE and FEMA formed the Flood Protection Structure Accreditation Task Force (Task Force) in accordance with Section 100226 of Public Law (P.L.) 112-141. The primary charge of the Task Force was to align agency processes, so information collected for either program can be used interchangeably and to align the information and data collected by USACE, so it is sufficient to satisfy NFIP accreditation requirements. The Task Force resulted in a list of recommendations and a formal memorandum of understanding signed by USACE and FEMA committing to establishing a coordinated approach for levee activities that is aligned with policies and goals of both agencies to promote life safety, flood risk reduction, risk communication, and sound national investments. The final Task Force report and memorandum of understanding can be found at https://www.usace.army.mil/Missions/Civil-Works/Levee-Safety-Program/Task-Force/.

1.3.3 National Academy of Science Recommendations

The National Research Council (NRC) document titled A Levee Policy for the National Flood Insurance Program, published in 1982, made recommendations to FEMA for a comprehensive levee policy for use in administering floodplain management, insurance, and hazard mapping https://www.usace.army.mil/National-Levee-Safety/ https://www.usace.army.mil/Missions/Civil-Works/Levee-Safety-Program/Task-Force/

Guidance Document 95 Page 6 aspects of the NFIP. The document addressed five areas that NRC deemed critical to a levee policy: (1) Minimum design standards; (2) Inspection and evaluation to be conducted by FEMA to assure conformance with minimum design standards at the time a levee is recognized in the program; (3) Requirements FEMA should place on communities with recognized levees; (4) Estimation of risk in areas landward of levees for use in setting insurance rates; and (5) Floodplain mapping of levee-impacted areas to portray SFHAs, degree of flood risk, and evacuation routes.

The National Academy of Sciences (NAS) document titled Levees and the National Flood Insurance Program, Improving Policies and Practices, published in 2013, examines the way levees are addressed in the NFIP and provides advice as to what actions might be taken to improve program efficiency and effectiveness. The NAS document includes 11 recommendations and 10 conclusions to improve the policies and practices related to levees and the NFIP.

Additional information on the NAS document is accessible through the NAS website at https://nas-sites.org/levees/. While FEMA is making progress toward achieving some of the goals and objectives, this guidance document does not address the modern risk-informed analysis recommended in the NAS document.

1.4 Levee-Related Communication and Community Engagement

To appropriately analyze and map the flood hazards in levee-impacted areas, FEMA will coordinate with communities during the Discovery Phase of a Flood Risk project, and throughout the project lifecycle as necessary, to understand the location and impacts of levee systems. The current, effective FIRMs may inadvertently represent levee systems as providing flood hazard reduction or other impacts to the conveyance of floodwaters, and as such, may indicate a lesser flood hazard and corresponding risk than what may actually exist in these areas. Because communities and property owners may not be fully aware of the risk associated with levee systems, coordination with local stakeholders is essential to identify, analyze, and map the flood hazards associated with levee systems and to provide relevant information and tools to help them understand their flood risk and mitigation opportunities in these areas.

FEMA developed the Risk Communications and Risk MAP Playbook, also known as the Community Engagement and Risk Communication (CERC) Playbook, to focus on the value of outreach and community engagement in ensuring the successful delivery of the Risk MAP program goals and demonstrating how communication can facilitate an understanding of the value of mitigation and the importance of resilience. The Playbook provides guidance to FEMA, FEMA Risk MAP providers (primarily, the Production and Technical Services [PTS] and CERC providers), and CTPs on developing approaches that will ultimately motivate communities toward mitigation action throughout the Risk MAP lifecycle, including those communities impacted by levees.

Section 5 of the Playbook, “Risk Communication for Communities with Levees”, provides guidance on FEMA’s role regarding levees, how that role intersects with the roles of other agencies; and how to effectively communicate flood risk with respect to levees. The levee section of the Playbook includes information on the following topics:

• Levee Systems: Who Does What?

• What Is Risk Communication in Relation to Levees?

https://nas-sites.org/levees/ https://nas-sites.org/levees/

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• Why and How Does FEMA Map Flood Hazards for Levee-Impacted Areas?

• Risk Messaging for Levees

• Developing your Community Engagement Plan

• Building Resiliency

Project Team members should refer to the CERC Playbook for additional information about stakeholder engagement and links to examples, tools, and templates. The CERC Playbook can be accessed through the password-protected Risk Management Directorate SharePoint Portal or by contacting the FEMA Project Officer.

This guidance document focuses on mapping guidance and therefore does not cover risk communication in detail, although these are important portions of the flood hazard mapping project lifecycle.

1.5 Chapter Overviews

Primary topics covered by this guidance document include the collection and management of levee data; procedures for addressing accreditation, PALs, and non-accredited levees;

addressing the topic of evaluating and mapping flood hazards landward of non-levee features;

and coordination with USACE and other Federal agencies. Additional summary information for each chapter is provided in Subsections 1.5.1 through 1.5.8

1.5.1 Chapter 2, Glossary of Levee Terms

The glossary in Chapter 2 contains levee terminology to be used throughout this guidance document.

1.5.2 Chapter 3, Levee Data Inventory

Chapter 3 provides an overview and brief history of FEMA historic levee inventory systems. The chapter introduces FEMA’s overall mission with early identification of levees, levee data tracking, inventory, mapping, and coordination/cooperation with USACE in the direction toward a unified national levee database. Chapter 3 provides guidance for populating and maintaining the FEMA accreditation status tracking system, the NLD, and National Flood Hazard Layer (NFHL).

1.5.3 Chapter 4, Accredited Levee Systems

Chapter 4 provides focused guidance on levee accreditation, leveraging the requirements in 44 CFR 65.10 and the transformation of PM 45, Revisions to Accredited Levee and Provisionally Accredited Levee Notation, issued on May 12, 2008; and PM 63, Guidance for Reviewing Levee Accreditation Submittals, issued on September 2, 2010. In addition to the transformed guidance, Chapter 4 includes clarifications and best practices that have been collected since the implementation of PMs 45 and 63.

1.5.4 Chapter 5, Provisionally Accredited Levees

Chapter 5 provides guidance to Project Team members (FEMA, FEMA Risk MAP providers, CTPs, and CTP subcontractors) on implementing the PAL process. This chapter is a transformation and revision of PM 43, Guidelines for Identifying Provisionally Accredited Levees, issued on September 25, 2006; PM 45, Revisions to Accredited Levee and Provisionally

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Accredited Levee Notation, issued on May 12, 2008; and PM 53, Guidelines for Notification and Mapping of Expiring Provisionally Accredited Levee Designations, issued on April 24, 2009.

1.5.5 Chapter 6, Non-Accredited Levees

Chapter 6 provides guidance to FEMA Regional Office staff, FEMA Risk MAP providers, CTPs, and CTP subcontractors involved in performing flood hazard mapping projects where non-accredited levee systems have been identified. This chapter follows the levee analysis and mapping procedures described in OG 12-13, Non-Accredited Levee Analysis and Mapping Guidance, dated September 2013.

1.5.6 Chapter 7, Non-Levee Features

Chapter 7 recommends actions that would help ensure adequate identification, analysis, and mapping of potential flood hazards around non-levee features. This chapter is a transformation and revision of PM 51, Guidance for Mapping of Non-Levee Embankments Previously Identified as Accredited, issued on February 27, 2009.

1.5.7 Chapter 8, FEMA and Other Federal Agency Coordination

Chapter 8 provides guidance to FEMA Regional Office staff, Risk MAP providers, and CTPs performing flood hazard mapping projects where other Federal agencies may have a role. These potential roles could include policy development, actual mapping actions, and accreditation efforts involving levees. In addition, mitigation and outreach activities may involve other Federal agencies.

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2.0 Glossary

Key levee terms used throughout this guidance document. are defined in Table 1.

Table 1: Levee Terms

Levee Term Description

Accredited Levee System A levee system shown on a FIRM that is recognized as reducing the f lood hazards posed by a base f lood. This determination is based on the submittal of data and documentation as required by 44 CFR 65.10. The area landward of an accredited levee system is shown as Zone X (shaded) on the FIRM except for areas of residual f looding, such as ponding areas, which are shown as

SFHA.

Berms Horizontal strips or shelves of material built contiguous to the base of either side of levee embankments for the purpose of providing risk reduction f rom underseepage or erosion or increasing the stability of the slopes of the earthen embankment.

Certif ication As stated in 44 CFR 65.2(b), certif ication of analyses is a statement that the analyses have been performed correctly and in accordance with sound engineering practices. Certif ication of structural works is a statement that works are designed in accordance with sound engineering practices to provide risk reduction f rom the base f lood. Certif ication of “as built” conditions is a statement that the structure(s) has been built according to the plans being certif ied is in place and is fully functioning.

Certif ication documentation is the responsibility of the local project sponsor.

Closure Devices Any movable and essentially watertight barriers, used during f lood periods to close openings in levee systems, securing but not increasing the levee systems’ design level of risk reduction.

Must be structural parts of the system during operation and designed according to sound engineering practice.

Erosion The wearing away of land masses through gradual natural processes or catastrophic events.

Flood Risk The risk of f looding in a leveed area that remains at any point in time af ter accounting for the f lood risk reduction contributed by the levee system. Risk is a measure of the probability and severity of undesirable consequences. Flood risk is comprised of three parts: (1) the likelihood of occurrence of an event (e.g., f lood, earthquake, etc.), (2) the likelihood associated with the performance of the levee system (e.g., levee breach, closure malfunction, overtopping, etc.), and (3) the magnitude of the consequences resulting f rom inundation of the levee impacted

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Levee Term Description area during that event (e.g., life loss, economic damages, environmental damages, etc.).

Floodwall A designed structural wall constructed adjacent to shorelines for the purpose of reducing f looding of property on the landward side of the wall. Floodwalls are normally constructed in lieu of or to supplement levees where the land required for levee construction is too expensive or not available.

Freeboard A factor of safety usually expressed in feet above a f lood level for purposes of f loodplain management. ”Freeboard’’ tends to compensate for the many unknown factors that could contribute to f lood heights greater than the height calculated for a selected size f lood and f loodway conditions, such as wave action, bridge openings, and the hydrological ef fect of urbanization of the watershed. At times, overbuild to account for long-term settlement and incrementing the height to ensure maintenance access during f lood events is referred to as f reeboard as well.

For levees and purposes of the NFIP, this is the vertical distance between the top of a levee and the water level that can be expected during the base f lood.

Freeboard Def icient Procedure Non-accredited levee analysis and mapping procedure that is applicable if the f reeboard requirement is not met, but the top of levee is above the base f lood. A Freeboard Def icient levee reach must meet the structural requirements of 44 CFR 65.10 and have documented operation, maintenance, and emergency preparedness plans. Freeboard Def icient Levee reaches dif fer f rom an accredited levee system because they are part of a levee system that as a whole cannot meet accreditation requirements and because they cannot meet the regulatory f reeboard standard.

Gravity outlets Culverts, conduits, or other similar conveyance openings through embankments or f loodwalls that permit discharge of interior f loodwaters by gravity when the outlets are above exterior water levels. Gravity outlets are equipped with gates to prevent f lows f rom entering the levee impacted area during time of high exterior stages.

Hazard An event or physical condition that has the potential to cause fatalities, injuries, property damage, inf rastructure damage, agricultural loss, damage to the environment, interruption of business, and other types of loss or harm.

Hydraulic Analysis An engineering analysis of a f looding source carried out to determine how f lood waters will move within the system in response to dif fering discharge quantities.

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Levee Term Description

Hydraulic Independence Two levees or levee reaches are considered hydraulically independent when their level of f lood hazard reduction functions independently f rom the other; their corresponding levee impacted areas are not identical; and if one breaches or overtops, the structural integrity of the other levee/levee reach is not adversely impacted.

Hydraulically Insignif icant For mapping purposes, a structure is considered hydraulically insignif icant if , during a 1-percent–annual-chance f lood event, the peak water-surface elevations landward of the structure may be the same regardless of whether the structure was in place.

Inspection A visual assessment of physical features of a levee system to determine the general condition and operability of the levee. This may include operation and mechanical features such as pumps or gates.

Interior Drainage Natural or modif ied removal of runof f within an area landward of a levee.

Interior Drainage Systems Systems associated with levee systems that usually include storage areas, gravity outlets, pumping stations, or a combination thereof to control interior drainage.

Levee Per 44 CFR 59.1, a manmade structure, usually an earthen embankment, designed and constructed in accordance with sound engineering practices to contain, control, or divert the f low of water to reduce f lood hazards posed by temporary f looding.

Leveed Area A spatial feature in the National Levee Database def ined by the lands f rom which f loodwater is excluded by the levee system.

Levee Breach A rupture, break, or gap in a levee system that causes f looding in the area landward of the levee system and may be due to overtopping or levee feature failure.

Levee Feature A structure that is critical to the functioning of a levee system, including: (A) an embankment section; (B) a f loodwall section;

(C) a closure structure; (D) a pumping station; (E) an interior drainage work; and (F) a f lood damage reduction channel.

Levee Impacted Area (for base flood)

The area landward of a levee system that would be inundated by the corresponding base f lood if the f lood hazard reduction ef fect of the levee system is not considered. Of ten, this area will be identif ied by applying the Natural Valley Procedure for the levee system.

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Levee Term Description

Levee Owner A federal or state agency, a water management or f lood control district, a local community, a levee district, a nonpublic organization, or an individual considered the proprietor of a levee. The levee owner is responsible for administering the operations, maintenance, and emergency preparedness plans for the levee system. Of ten referred to as levee sponsor.

Levee Reach A levee reach is a portion of a levee system (usually a length of a levee) that may be considered for analysis purposes to have approximately uniform representative properties. A levee reach is a unique component having properties dif ferent than other reaches of the levee system and may be used to evaluate the performance of a portion of the levee system. No minimum or maximum length is associated with a reach. Any continuous section of a levee to which a single analysis and mapping procedure may be considered as a reach.

Levee Segment A discrete portion of a levee system that is operated and maintained by a single entity. A levee segment can be comprised of a single levee reach or multiple reaches. A levee segment may comprise one or more levee feature.

Levee System A f lood hazard-reduction system that consists of one or more levee segments/reaches and other features, such as f loodwalls and pump stations, which are interconnected and necessary to ensure exclusion of the design f lood f rom the associated hydraulically independent levee impacted area, and which are constructed and operated in accordance with sound engineering practices.

Line of Flood Hazard Reduction The centerline of the levee segments/reaches which exclude f loodwaters f rom the base f lood event f rom the levee impacted area.

Local Levee Partnership Team

(LLPT)

A workgroup that is facilitated by FEMA when a levee system will be analyzed by levee analysis and mapping procedures for non-accredited levees. The primary function of this group is to share information/data and identify options based on stakeholder roles and knowledge.

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Levee Term Description

National Levee Database (NLD) The NLD, developed by the USACE in cooperation with FEMA, is a dynamic, searchable inventory of information for all levee systems in the nation. The database contains information to facilitate and link activities, such as f lood risk communication, levee system evaluation for the NFIP, levee system inspections, f loodplain management, and risk assessments. The NLD continues to be a dynamic database with ongoing ef forts to add levee data f rom federal agencies, states and tribes.

Natural Valley Procedure Non-accredited levee procedure that can be applied to all non-accredited levee reaches. The Natural Valley Procedure is used in two ways: f irst landward of the entire levee system to determine the outer limits of any levee impacted Zone D areas, and second as a potential procedure applied to individual levee reaches to determine the SFHA on the landward side of the levee reach. Several factors are considered when determining whether to use the Natural Valley Procedure to determine the

SFHA:

• The levee reach does not signif icantly obstruct the f low of water;

Data necessary for more complex methods is not and will not be available in the near term; or

• The community (or tribal entity, when appropriate) provides feedback that it is the acceptable procedure to use.

For riverine levee systems, the Natural Valley Procedure ref lects the levee geometry in the hydraulic model but allows water to f low on either side of the levee. For coastal levee systems, the Natural Valley Procedure ref lects the levee geometry, and consideration is given as to how the levee system impacts wave propagation.

Non-Accredited Levee System A levee system that does not meet the requirements in the NFIP regulations at Title 44, Chapter 1, Section 65.10 of the Code of Federal Regulations (44 CFR 65.10), Mapping of Areas Protected by Levee Systems, and is not shown on a FIRM as reducing the base f lood hazards.

Non-levee Feature A physical feature that is not designed, constructed, operated, or maintained as a f lood control structure, but may inadvertently conf ine f low during some f lood events.

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Levee Term Description

Non-levee Reach A form of manmade high ground which a levee system or segment/reach ties into, whose existence and performance is necessary for excluding f loodwaters f rom the levee impacted area.

Overtopping A condition that occurs when water levels, including any wave or run-up factors, exceed the top elevation of a levee system and f low into areas landward of the levee system. Levee system may be damaged and/or compromised.

Overtopping Procedure Non-accredited levee procedure is applicable when the base f lood is above the levee crest for a reach, and the community or levee owner has provided appropriate technical justif ication that the base f lood event will not cause a levee breach. In addition to the structural standards established in 44 CFR 65.10, it is expected that more detailed structural analysis will be required to justify that the levee system can sustain the base f lood. As with a Sound Reach and Freeboard Def icient levee reach, an operations and maintenance plan and documentation of inspection are required.

Piping The result of water seepage that progressively erodes and washes away soil particles, leaving large voids in the soil.

Removal of soil through sand boils by piping or internal erosion damages levees, their foundations, or both, which may result in settlement and has the potential to cause catastrophic failures of levees.

Ponding The result of runof f or f lows collecting in a depression that may have no outlet, subterranean outlets, rim outlets, or manmade outlets such as culverts or pumping stations. Impoundments landward of manmade obstructions are included in this type of shallow f looding as long as they are not backwater f rom a def ined channel or do not exceed 3.0 feet in depth.

Provisionally Accredited Levee

(PAL)

A designation for a levee system that FEMA has previously accredited with reducing the f lood hazards associated with a base f lood on an ef fective FIRM, and for which FEMA is awaiting data and/or documentation that will demonstrate the levee system’s compliance with the NFIP regulatory criteria of 44 CFR 65.10.

Pumping Stations Pumps located at or near the levee system to discharge interior drainage over or through the levees or f loodwalls (or through pressure lines) when f ree outf low through gravity outlets is prevented by high exterior stages.

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Levee Term Description

Rehabilitation The term rehabilitation means the repair, replacement, reconstruction, or reconf iguration of a levee system, including a setback levee.

Residual Risk (or Flood risk) The f lood risk (probability of capacity exceedance or failure and the associated consequences) that remains af ter the f lood risk management measure is implemented.

Ring Levees Levees that completely encircle or “ring” an area subject to inundation f rom all directions.

Risk Assessment A systematic, evidence-based approach for quantifying and describing the nature, likelihood, and magnitude of risk.

Setback Levees Levees that are built landward of existing levees, usually because the existing levees have suf fered distress or are in some way being endangered, as by river migration.

Shallow Flooding Flat areas where a lack of channels prevents water f rom draining away easily. Shallow f lood types fall into three categories: sheet f low, ponding, and urban drainage. For the purposes of the NFIP, shallow f looding is distinguishable f rom riverine or coastal f looding because it generally occurs in an area where there is no channel or identif iable f low path.

Sound Reach Procedure A reach that has been designed, constructed, and maintained to withstand the f lood hazards posed by a base f lood, in accordance with the standards in 44 CFR 65.10 of the NFIP regulations, but is part of a system that cannot be accredited.

Structural-Based Inundation Procedure

Non-accredited levee analysis and mapping procedure applicable to some levee systems having reaches with either structural def iciencies that are known or structural integrity that is unknown (a common occurrence for older levee systems). For these levee reaches, FEMA will rely on modeling of breaches along the levee reach. It is not possible to predict the exact location of a levee breach. This procedure, therefore, does not predict the probability of failure at any breach location, nor does it provide a specif ic determination or evaluation of the overall levee system performance or require a determination of the likely failure mechanism. The procedure instead results in the development of a levee reach-specif ic SFHA that might occur as a result of potential breaches along a particular levee reach during the base f lood. To determine this SFHA, possible locations of system breaches, geometry, and failure duration will be considered.

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Levee Term Description

Zone A99 As def ined in 44 CFR 61.12, areas subject to inundation by the base f lood event, but which will ultimately be accredited upon completion of an under-construction levee system. These are areas of special f lood hazard where enough progress has been made on the construction of a levee system, such as dikes, dams, and levees, to consider it complete for insurance rating purposes. Zone A99 may only be used when the levee system has reached specif ied statutory progress toward completion. No BFEs or depths are shown. Mandatory f lood insurance purchase requirements and f loodplain management standards apply.

Zone AR As def ined in 44 CFR 61.12, areas that result f rom the new non-accredited status of a previously accredited levee system that is determined to be in the process of being restored to provide base f lood risk reduction. Mandatory f lood insurance purchase requirements and f loodplain management standards apply.

Zone D An area of possible, but undetermined f lood hazard. When analyzing and mapping areas landward of non-accredited levee systems, a Zone D may represent areas landward of a non-accredited levee, within the natural valley footprint, that are not depicted as SFHA resulting f rom f reeboard def icient, sound reach, overtopping, and/or structural-based inundation procedures. The Zone D designation is used for non-accredited systems instead of the Zone X (shaded) designation because the f lood hazard potential is more uncertain and possibly greater.

3.0 Levee Data Inventory

The construction of flood hazard-reduction structures, such as levees and floodwalls, has had a significant effect on flood-prone areas throughout the United States. These structures are of particular importance in identifying flood hazards and risks to lives and property. As such, FEMA and USACE share a common interest in managing and administering levee information and data throughout the Nation.