Federal Emergency Management Agency 

Washington, D.C. 20472 

MEMORANDUM FOR: 


FROM: 


Mitigation Division Directors 
Risk Identification Branch 
SUBJECT: Procedure Memorandum No. 37 -Protocol for Atlantic and 
Gulf Coast Coastal Flood Insurance Studies in FY05 

Background: Atlantic and Gulf Coast coastal Flood Insurance Studies 
Fiscal Year (FY) 2005 can be initiated using knowledge gained and recommendations 
made by the Technical Working Group for the Pacific Coast Study Guidance project 
conducted over the past year and a half. This project, led by Region was a 
cooperative effort between FEMA Headquarters and Regional offices to develop new 
technical guidance for Pacific Coast flood studies and to review possible updates and 
revisions to existing flood study guidance for the Atlantic and Gulf coasts. This 
Procedure Memorandum presents revisions and modifications to existing protocols in 
Appendix D: Guidelines for Coastal Flooding Analyses and Mapping (April 2003) for 
performing detailed coastal hazard assessments for communities along the Atlantic and 
Gulf Coasts. 


This Procedure Memorandum is considered an addendum to Appendix D and a 
component within the scope of work for coastal FISs initiated in FY 2005 by Regional 
Mapping Partners Quantity (IDIQ) or Cooperating 

and VI. These procedural changes 
affect only guidance to subsections listed below and found in section D.2 of Appendix D, 
entitled 


Elevation Determination and V Zone Mapping: Gulf of Mexico and 
Atlantic Ocean"(February 2002). The basis for these procedural changes can be found in 
the Pacific Coast Study Guidance project final Phase 1 Summary Report and appendices, 
entitled 


Coastal Flood Hazard Analysis and Mapping Phase 1 Summary Report, 
dated February 2005. The final Phase 1 Summary Report covers topics reviewed by the 
Technical Working Group related to individual coastal processes or methodologies 
applied during coastal flood studies for the National Flood Insurance Program 
Recommendations for improving existing Appendix D guidance for the Atlantic and Gulf 
Coasts are presented in each of these appendixes. While some of the following 
recommendations have not been thoroughly tested, the Technical 


Group and 
other technical experts in the field all agreed that these are the best approaches. 

in 
Technical Partner (CTP)) in Regions I, 

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For Regions 


and X, the guidance and updates to Appendix D presented in the Phase 2 
(November 2004) draft of the Pacific Guidelines entitled 
Draft Guidelines for 
Coastal Flood Hazard Analysis and Mapping for the 


Coast of the United States" 
are recommended for use and application for Pacific Coast flood studies. The methods 
and technical approaches in the draft Phase 2 Pacific Guidelines will also be considered 
for supplemental recommendations to applications within the Atlantic and Gulf Coast 
regions after any necessary refinement and testing. A review and update to the coastal 
guidance for the Great Lakes region is underway currently in Region V. 

The following guidance is provided for each of the key technical issues of concern to on-
going or planned coastal floods studies in the Atlantic and Gulf Coasts. 

Issue 1: Stillwater Elevations (Section D.2.2.1 "Stillwater Elevations") 

The only guidance in Appendix D for stillwater elevation determination using tide gage 
data is a requirement for at least 20 years of recorded tide gage station data. No guidance 
is available on the statistical methods that should be considered in developing 
frequency analyses of long-term tide gage data. The Phase 1 Summary Report appendix 
on stillwater elevations, entitled "Stillwater: FEMA Coastal Flood Hazard Analysis and 
Mapping Guidelines Focused Study Report, 


recommends the development of new 
guidance to assist Regional Mapping Partners on these types of assessments. 
Action Procedure: In section D.4.3 of the draft Pacific Guidelines on 
Flood Frequency Analysis Methods, basic statistical tools and methods are outlined to 
analyze long-term tide gage records for stage-fi-equency assessments. In addition, 
subsection D.4.4.2 of the draft Pacific Guidelines includes an outline of methods to 
determine water-level statistics. These approaches are all based on standard statistical 
techniques and represent the best available guidance to be applied to coastal 


when 
stillwater elevations are revised using an analysis of long-term tide gage records. 

Issue 2: Coastal Structures (Section D.2.3, "Evaluation of Coastal Structures") 

The principal guidance related to evaluating whether coastal structures provide protection 
during the 1-percent-annual-chance (base) flood can be found in Appendix D section 2.3. 
If a coastal structure can be certified and is expected to survive the 
chance flood, the structure should be included in all ensuing analyses of wave effects 
(erosion, 


and wave height). Otherwise, it should be considered destroyed before 
the 1-percent-annual-chance flood and removed from subsequent representations. 
However, Appendix D provides no specific guidance on how to remove failed coastal 
structures or how to consider their interactions with storm surge inundation, wave 
overland wave propagation, and overtopping. Because remnants of failed coastal 
structures can remain in place during severe coastal flood events, the Phase 1 Summary 
Report appendix on coastal structures, entitled "Coastal Structures: FEMA Coastal 
Flood Hazard Analysis and Mapping Guidelines Focused Study Report, 


recommends 
methods for treating failed coastal structures. The focused study also points out an 
inconsistency between the evaluation criteria for existing structures during a coastal 

Page 3 of 7 -Procedure Memorandum 37 

Flood Insurance Study (FIS) and those used for 


existing structures in a Letter of 
Map Revision (LOMR). 

Action Procedure: The Phase 1 Summary Report focused study on 
coastal structures includes new procedures for dealing with failed coastal structures and 

existing structures for a coastal FIS or LOMR. These procedures should be 
made available to and evaluated by Regional Mapping Partners during studies started in 
FY 2005. 


Issue 3: Storm (Section D.2.2.6, "Storm 
There is no current explicit guidance in Appendix D on combination of coastal storm 
surge and astronomical tides or on statistical combination of coastal storm surge inland 
profile with the riverine profile (assuming independence of the processes). However, 
suitable techniques for combination of surge and tide during the surge numerical 
modeling process are contained in the user's manuals that support particular surge 
models. The Phase 1 Summary Report appendix on storm meteorology, entitled "Storm 
Meteorology: 

Coastal Flood Hazard Analysis and Mapping Guidelines Focused 
Study Report, recommends additional studies and development of new guidance. 

Action Procedure: General methods addressing these issues are 
included in the 


Pacific Guidelines in sections D.4.2 on Study Methodology and D. 

4.3 on Flood Frequency Analysis Methods. These methods should be considered the best 
available information and guidance for studies requiring similar storm meteorology work 
elements for an Atlantic or Gulf Coast study. 
Issue 4: Wave Transformation (Section D.2.2.7, "Storm Wave Characteristics") 

Appendix D includes very limited existing guidance when wave transformation (wave 


shoaling, and dissipation) calculations are needed or how they 
should be performed for an FIS. The Phase 1 Summary Report appendix on wave 
transformation, entitled "Wave Transformation: 

Coastal Flood Hazard Analysis 
and Mapping Guidelines Focused Study Report, determined that wave transformation 
would be of greatest concern in a coastal FIS within sheltered waters. The focused study 
recommends evaluating and developing general guidance on wave transformation, 
including wave energy dissipation over shallow flat bottoms found in sheltered waters 
along the Atlantic and Gulf Coasts. 

Action Procedure: Complex wave transformation assessments and 
modeling are not considered necessary in the open coast environment of the Atlantic and 
Gulf Coast regions, where waves and surge are generally concurrent with 
peak flood events along uniformly sloping beaches. However, wave transformations may 
be important for wave penetration into a bay or for wave generation within bays and 
sheltered waterways. If the Regional Mapping Partner determines that wave 
transformation may have a significant impact on the coastal hazards in the study area, 
wave transformation methods should be applied on an as-needed basis following 



of the 
Page 4 of 7 -Procedure Memorandum 37 

guidance in Chapters 2 and 3 in Volume I of the U.S. Army Corps of Engineers 
1984 Shore Protection Manual (SPM), or in Sections 2 and 4 of Chapter 3 in Part 
2003 Coastal Engineering Manual (CEM). These procedures should be compared to 

determine the most cost effective and accurate approach. If two-dimensional 
the accepted coastal models list 
or meet the approval criteria specified in the 

Issue 5: Storm-Induced Erosion (Section D.2.4.1. "Basic Erosion Considerations") 

A long-term recommendation from the Technical Working Group included in the Phase 1 
Summary Report appendix on erosion, entitled "Event-Based Erosion: Coastal 
Flood Hazard Analysis and Mapping Guidelines Focused Study Report, 

consider analyzing new pre-and post-storm profiles to update the data used to develop 
the 540-square-foot (sf) erosion criteria as a representative erosion area for the 100-year 
storm event. However, further testing will be required before this can be implemented 
into coastal studies. 

Action Procedure: Until the recommended erosion storm data and 
profiles can be assessed, the existing 540-sf criteria should continue to be used for 
storm-induced erosion assessments. If historical erosion data support use of a different 
erosion value (other than the 540-sf value), the supporting data should be 
reviewed and any revised values approved by the Regional office before a different value 
can be applied in a coastal FIS. 

Issue 6: Wave (Section "Wave Model Description") 

The Phase 1 Summary Report appendix on wave entitled "Wave and 
Overtopping: FEMA Coastal Flood Hazard Analysis and Mapping Guidelines Focused 
Study Report, and draft Pacific Guidelines both provide recommendations that mean 
wave conditions and mean wave values no longer be used for coastal flood studies. 
In the reports, it is recommended that analyses and mapping of stillwater and wave 
elevations should reflect the 2-percent wave depth rather than the mean 
(50-percent) wave depth. This would require use of an interim procedure to 

2.0 model results until other procedures can be implemented. The interim wave 
procedure would scale the 2.0 model results based on accepted statistical 
distributions of wave In section D.4.5 of the draft Pacific Guidelines, alternative 
approaches to analyzing wave include both the Automated Coastal 
Engineering Software (ACES) approach and the approach referred to as the TAW 
(Technical Advisory Committee for Water Retaining Structures) method (which serves as 
the basis for CEM calculations). Section D.4.5 of the draft Pacific Guidelines also 
recommends and provides details on an integrated approach that combines wave setup 
(static and dynamic) and wave referred to as the Direct Integration Method (DIM). 

Action Procedure: The integrated approach to combine wave and 
setup approach) described in section D.4.5 of the draft Pacific Guidelines may 
eventually serve as a replacement for conventional wave setup and 2.0 model 

numerical models are used, they should be selected 
regulations. 
is that FEMA 

Page 5 of 7 -Procedure Memorandum 37 

analyses for the Atlantic and Gulf coasts. However, this method has not been tested or 
applied in a coastal FIS. In the interim, it is recommended that the 2-percent wave 
value be used for Base Flood Elevation determination and hazard mapping for the 
Atlantic and Gulf Coasts. This can be accomplished through scaling or conversion of the 


2.0 model mean results to the 2% value, or direct computation of the 2% wave 
using the ACES or TAW methods. 
Issue 7: Wave Setup (Section D.2.5.6, "Wave Setup") 

The recommended approach for calculating wave setup on the Pacific Coast is the DIM, 
through use of an equation or parametric method developed for and described in section 

D.4.5 of the draft Pacific Guidelines. At this time, the DIM is untested and has not been 
applied in a coastal FIS, so it has not been recommended for use in the Atlantic and Gulf 
Coasts. 
Action Procedure: As an interim method, the use of guidance 
the SPM as currently recommended in Appendix D is to be used for wave setup 
calculations along the Atlantic and Gulf Coasts. The Regional office should be consulted 
regarding any exceptions to this interim method. The Regional Mapping Partner should 
determine which method provides the most cost effective and technically accurate result 
for application in the study and coordinate with the Regional office accordingly. 

Issue 8: Wave 


(Section D.2.5.7, "Wave Overtopping") 

The Phase 1 Summary Report appendix on wave overtopping, entitled "Wave 


and 
Overtopping: FEMA Coastal Flood Hazard Analysis and Mapping Guidelines Focused 
Study Report, 


recommends continued use of the mean wave overtopping rate (as 
contained in Appendix D) and also the testing of available alternate overtopping methods 
to select the best method The wave overtopping approach developed in section D.4.5 of 
the draft Pacific Guidelines links wave 
and overtopping directly, and uses a 
trajectory analysis to determine the wave-overtopping water-surface profile. The new 
method also uses overtopping flood depth and velocity to define Zone VE using a new 
criterion. 

Action Procedure: The new overtopping calculation methods proposed 
in the draft Pacific Guidelines should not be applied to the Atlantic and Gulf Coasts until 
testing in a coastal FIS has been completed. Therefore, continued use of existing 
Appendix D methods is required at this time. 


Issue 9: Wave Heights (Section D.2.6, "Analysis of Overland Wave Dimensions") 

As part of the Phase 1 Summary Report appendix on wave transformation, entitled 

"Wave Transformation: Coastal Flood Hazard Analysis and Mapping Guidelines 
Focused Study Report, a number of changes to the 3.0 model were proposed 
that would be useful in all coastal regions, but the basic methodology and approach 
remain unchanged. There are several proposed changes to the WHAFIS 3.0 model that 


Page 6 of 7 -Procedure Memorandum 37 

are described in the report, but the WHAFIS 3.0 model code has not yet been revised to 
reflect those changes. Further evaluation during the preparation of the 

Pacific 
Guidelines resulted in the development of a revised version of the WHAFIS 3.0 model, 
which allows for variable wind speed inputs for wave growth calculations other than the 
fixed open water and inland fetch wind speeds. 

Action Procedure: The revised version of WHAFIS 3.0 has not been 
tested and approved for use on the Atlantic and Gulf Coasts. When approved, it would 
only be appropriate in special situations, primarily in the sheltered waters of inland bays 
and estuaries. In the interim, the current version of the WHAFIS 3.0 model and its wind 
speed defaults are required for all coastal FISs with overland wave propagation analyses 
along the Atlantic and Gulf Coasts. 

Issue 10: Hazard Zone Mapping (Section D.2.7.1, "Review and Evaluation of Basic 
Results") 

The Phase 1 Summary Report appendix on hazard zone mapping, entitled "Flood Hazard 
Zones: FEMA Coastal Flood Hazard Analysis and Mapping Guidelines Focused Study 
Report, 

recommends only minor changes to flood hazard zone mapping procedures. A 
new VE zone criterion (based on flood depth and velocity) was proposed, but it has not 
yet been evaluated or approved. 

Action Procedure: No significant changes in the mapping of hazard 
zones have been recommended, so the existing Appendix D guidance is adequate for all 
Atlantic and Gulf Coast FISs in FY 2005. 


11: Dune VE Zone Mapping 
Flood Insurance Risk Zones") 
The recommendations in the Phase 1 Summary Report appendix on hazard zone 
mapping, entitled "Flood Hazard Zones: Coastal Flood Hazard Analysis and 
Mapping Guidelines Focused Study Report, called for regulatory changes to the NFIP to 
revise mapping procedures for primary dunes in instances where high-profile 
coastal ridges or plateaus back the shoreline. The report also mentions adoption of a 
technique for quantitative primary 


dune mapping. 

Action Procedure: Implementing changes to primary 


dune 
identification and mapping criteria will not be made at this time. Therefore, the 
continued use of existing Appendix D guidance is required for all coastal FISs along the 
Atlantic and Gulf Coasts. 

cc: See distribution list 

Page 7 of 7 -Procedure Memorandum 37 

Distribution List (electronic distribution only) 
Office of the Mitigation Division Director 
Risk Assessment Branch 
Risk Identification Branch 
Flood Insurance and Mitigation Divisions in FEMA Regional Offices 
Office of Legislative Affairs 
Office of General Counsel 
National Service Provider 
Systems Engineering and Technical Assistance Contractor 
Map Service Center