Issues, Remedies, and Research
Needs Related to Dam Service
and/or Emergency Spillways

Proceedings FEMA Workshop
August 26-27, 2003
Denver Colorado

U.S. Department of the Interior
Bureau of Reclamation
Denver, Colorado June 2004

Preface

One of the activities authorized by the Dam Safety and Security Act of 2002 is research to enhance the Nations ability to assure that adequate dam safety programs and practices are in place throughout the United States. The Act of 2002 states that the Director of the Federal Emergency Management Agency (FEMA), in cooperation with the National Dam Safety Review Board (Review Board), shall carry out a program of technical and archival research to develop and support:

improved techniques, historical experience, and equipment for rapid and effective dam construction, rehabilitation, and inspection;
devices for continued monitoring of the safety of dams;
development and maintenance of information resources systems needed to support managing the safety of dams; and
initiatives to guide the formulation of effective policy and advance improvements in dam safety engineering, security, and management.

With the funding authorized by the Congress, the goal of the Review Board and the Dam Safety Research Work Group (Work Group) is to encourage research in those areas expected to make significant contributions to improving the safety and security of dams throughout the United States. The Work Group (formerly the Research Subcommittee of the Interagency Committee on Dam Safety) met initially in February 1998. To identify and prioritize research needs, the Subcommittee sponsored a workshop on Research Needs in Dam Safety in Washington D.C. in April 1999. Representatives of state and federal agencies, academia, and private industry attended the workshop. Seventeen broad area topics related to the research needs of the dam safety community were identified.

To more fully develop the research needs identified, the Research Subcommittee subsequently sponsored a series of nine workshops. Each workshop addressed a broad research topic (listed below) identified in the initial workshop. Experts attending the workshops included international representatives as well as representatives of state, federal, and private organizations within the United States.

Impacts of Plants and Animals on Earthen Dams
Risk Assessment for Dams
Spillway Gates
Seepage through Embankment Dams
Embankment Dam Failure Analysis
Hydrologic Issues for Dams
Dam Spillways
Seismic Issues for Dams
Dam Outlet Works

In April 2003, the Work Group developed a 5-year Strategic Plan that prioritizes research needs based on the results of the research workshops. The 5-year Strategic Plan ensures that priority will be given to those projects that demonstrate a high degree of collaboration and expertise, and the likelihood of producing products that will contribute to the safety of dams in the United States. As part of the Strategic Plan, the Work Group developed criteria for evaluating the research needs identified in the research workshops. Scoring criteria was broken down into three broad evaluation areas: value, technical scope, and product. The framework adopted by the Work Group involved the use of a decision quadrant to enable the National Dam Safety Program to move research along to produce easily developed, timely, and useful products in the near-term and to develop more difficult, but useful, research over a 5-year timeframe. The decision quadrant format also makes it possible to revisit research each year and to revise research priorities based on current needs and knowledge gained from ongoing research and other developments.

Based on the research workshops, research topics have been proposed and pursued. Several topics have progressed to products of use to the dam safety community, such as technical manuals and guidelines. For future research, it is the goal of the Work Group to expand dam safety research to other institutions and professionals performing research in this field.

The proceedings from the research workshops present a comprehensive and detailed discussion and analysis of the research topics addressed by the experts participating in the workshops. The participants at all of the research workshops are to be commended for their diligent and highly professional efforts on behalf of the National Dam Safety Program.

Acknowledgments

The National Dam Safety Program research needs workshop on Seepage through Embankment Dams was held on October 17-19, 2000, in Denver, Colorado.

The Department of Homeland Security, Federal Emergency Management Agency, would like to acknowledge the contributions of the Association of State Dam Safety Officials and URS Corporation in organizing the workshop and developing these workshop proceedings. A complete list of workshop facilitators, presenters, and participants is included in the proceedings.

MISSION STATEMENTS

The mission of the Department of the Interior is to protect and provide access
to our Nation's natural and cultural heritage and honor our trust responsibilities
to Indian tribes and our commitments to island communities.

The mission of the Bureau of Reclamation is to manage, develop, and protect
water and related resources in an environmentally and economically sound
manner in the interest of the American public.

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways

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Acknowledgements

The steering committee for the organization of the Issues, Remedies, and Research Needs
Related to Dam Service and/or Emergency Spillways included the following members:

Kathleen H. Frizell, Reclamation
Darrel Temple, USDA-ARS
David C. Campbell, Schnabel Engineering, Inc.
Charles Tate, USACE, ERDC
1Nathan Snorteland, Reclamation

Angela Medina and Cheryl Rieniets of Reclamations Water Resources Research
Laboratory greatly assisted by providing project management and administrative duties
including corresponding with participants, making local arrangements, and assisting with
setup on the day of the workshop.

Tom Cook, of Reclamations Estimating, Specifications, and Value Program Group,
provided facilitation for both days of the workshop and led all discussions.

Marianne Hartman, of MH Events, provided and ran the equipment to conduct voting
with remote keypads and instant feedback of the results (www.mhevents.net). The voting
was essential to the timely completion of the workshop.

Jorge Matos, Assistant Professor, Institute of Superior Technology, Lisbon was unable to
attend the workshop, but he provided valuable ideas regarding research needs from the
international standpoint.

All workshop speakers and participants diligently worked to make this event a success.

PROJECT SPONSOR

Federal Emergency Management Agency
National Dam Safety Program
Research Work Group, Bruce Muller (Reclamation), Chair
500 C Street SW
Washington, DC 20047

PROJECT COORDINATOR

U.S. Bureau of Reclamation
Denver Federal Center
PO Box 25007
Denver, CO 80225

1 This document was peer reviewed by Dave Campbell and Darrel Temple of the steering committee.

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways

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Abbreviations and Acronyms

ARS Agricultural Research Service
ASCE American Society of Civil Engineers
ASDSO Association of State Dam Safety Officials
D/B difficulty/benefit
ERDC Engineering Research and Development Center
FEMA Federal Emergency Management Agency
HB high benefit
HD high difficulty
HMR National Weather Service Hydrometeorological Report
ICODS Interagency Committee on Dam Safety
LB low benefit
LD low difficulty
NDSP National Dam Safety Program
NDT non-destructive techniques
NRCS Natural Resources Conservation Service
O&M operation and maintenance
PI principal investigator
PMF probable maximum flood
PMP probable maximum precipitation
RCC roller compacted concrete
Reclamation Bureau of Reclamation
REMR Repair, Evaluation, Maintenance, Rehabilitation
Review Board National Dam Safety Review Board
SITES Water Resources Site Analysis Program
strategic plan National Dam Safety Programs 5-Year Strategic Plan
the Act Dam Safety and Security Act of 2002
USACE U.S. Army Corps of Engineers
USDA U.S. Department of Agriculture
Work Group Dam Safety Research Work Group

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Table of Contents

Page
Overview. 1
Workshop Organization 2
State-of-Practice. 6
Workshop Presentations. 7
Hydraulic Design of Labyrinth Weirs and Fuse Gates 8
Fuse Plug Embankments - State of the Art and Practice, and Research Needs. 8
Crest Parapets and Dam Raising. 8
Gated Spillways: Enlargement, Modification, and Rehabilitation
State of Practice 8
Earthen Spillways: Design and AnalysisState of the Practice 9
Spillway Foundation Erosion. 9
Dam Overtopping Protection TechnologiesState of Practice and
Research Needs. 9
RCC Overtopping Protection for Increasing Spillway Capacity 9
General Discussion - NRCS Designs and Research Needs 10
Spillways: An Owners Perspective. 10
General DiscussionConsultant's Spillway Design and Research Needs. 10
Vegetated Earth SpillwaysInspection, Maintenance, and Monitoring. 10
Earth SpillwaysState of Practice and Research Needs 11
Issues and Research Needs Related to Hydraulics for State Regulated Dams 11
Concrete Spillway Repairs. 11
Inspection of Concrete SpillwaysGated and Uncontrolled. 11
Geophysics for Spillway and Seepage Evaluation. 12
Inspection, Maintenance, and Monitoring of Service and Emergency Spillways 12
Unlined Spillway Erosion Risk Assessment. 12
Summary 12
Research Needs. 13
Topic Development and Discussion 13
Evaluation of Research Needs 20
Voting 20
Decision Quadrant 20
Evaluation 21
Results. 27
Appendix A: Workshop Attendees
Appendix B: Abstracts
Appendix C: Presentations
Appendix D: References
Appendix E: Individual Topic Voting Results
Appendix F: Individual Evaluation Forms for Each Related Topic

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Tables

Page

1 Workshop steering committee members. 3
2 Agenda for the workshop. 5
3 Summary of workshop presentations by title and presenter for each
major workshop topic 6
4 Compilation of research needs topics with letter designations under
main category headings. 14
5 Evaluation criteria for research topics developed by the Dam Safety
Research Work Group. 23
6 Tabulated results of the difficulty/benefit voting and the group
evaluations for each research topic 28
7 Prioritized research needs topics developed by the workshop steering
committee from the workshop results. 32

Figures

Page

1 Research needs decision quadrant definition. 21
2 Decision quadrant results for each topic developed during the
brainstorming session. 22
3 Results of the evaluation ratings for each topic shown on the decision
quadrant for reference 29
4 Final research needs prioritization from steering committee
recommendations, based upon the decision quadrant location
and evaluation scores developed by the workshop participants 31
5 Cost of the recommended research topics from the workshop 33

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Overview

One of the key activities authorized by the Dam Safety and Security Act of 2002 (the
Act) is research to enhance the Nations ability to ensure adequate dam safety programs
and practices throughout the United States. With the funding authorized by the Congress,
the goal of the National Dam Safety Review Board (Review Board) and the Dam Safety
Research Work Group (Work Group) is to encourage research in those areas expected to
make significant contributions to improving the safety and security of dams throughout
the United States. Although there are many worthwhile research projects that can be
initiated, it was not intended by the Congress that the Act serve as the sole source of
funding for research in the field of dam safety.

To guide decisions regarding the funding of specific research projects, the Work Group
has developed a 5-Year Strategic Plan (strategic plan) that prioritizes research needs.2
While the plan provides a snapshot of the priorities at one point in time, it is a living
document that can be updated to reflect emerging needs and opportunities. The strategic
plan also provides a blueprint for the Work Group to use in developing annual work
plans. The goal of the Work Group in developing the 5-year strategic plan is to ensure
that priority will be given to those projects that demonstrate a high degree of
collaboration and expertise, and the likelihood of producing products that will contribute
to the safety and security of dams in the United States.

Much of the input to this strategic plan originated with the results of a number of
workshops sponsored by the Research Subcommittee of the Interagency Committee on
Dam Safety (ICODS).3 Funding provided under the National Dam Safety Act of 1996
enabled the Research Subcommittee to conduct the workshops, pursue highly valuable
research that could be accomplished in a short period of time, and pursue several other
opportunities to improve dam safety programs and processes. With many of the
workshops completed or nearing completion, the Work Group determined that there was
a need to develop a strategy for prioritizing the many research proposals being generated
by the workshops.

The Issues, Remedies, and Research Needs Related to Dam Service and/or Emergency
Spillways workshop was held to meet the requirements of the National Dam Safety
Program Act of 1996. This act called for the Director of the Federal Emergency
Management Agency (FEMA) to carry out a program of technical and archival research
to develop: (1) improved techniques, historical experiences, and equipment for rapid and
effective dam construction, rehabilitation, and inspection; and (2) devices for the
2 5-Year Strategic Plan (Draft), National Dam Safety Program, Dam Safety Research Work Group,
June 2003.
3 Upon passage of the Dam Safety and Security Act of 2002, the ICODS Research Subcommittee was
reformulated as the Dam Safety Research Work Group reporting to the National Review Board.

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

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continued monitoring of the safety of dams. The recommended research from this 
workshop will be presented in the format developed in the strategic plan. 

Workshop objectives were to: 

* Document the state-of-practice concerning cost-effective techniques for 
enlargement, modification, inspection, monitoring, and maintenance of dam 
service and/or emergency spillways 

* Access dam safety research needs: scope short-term and long-term needs of the 
Federal and non-Federal dam safety community 

* Recommend course of action to address the identified research needs 

Day one was dedicated to presentations of state-of-practice technologies by subject 
matter expects. Day two involved a facilitator, speakers, and invited participants who 
provided input on research needs related to the workshop objectives. 

This document outlines the procedures used to accomplish the workshop objectives and 
provides the final documentation of the proceedings including: 

* Topic presentations 

* Topic discussions 

* Research needs 

* Research needs prioritization 
- Benefit/difficulty voting 
- Evaluation 

* Research needs summary 

* Appendices of supporting documentation 

Workshop Organization 

The 2-day workshop on Issues, Remedies, and Research Needs Relating to Service and/or 
Emergency Spillways was held August 26-27, 2003, at the Bureau of Reclamation, 
Technical Services Center, Denver, Colorado. The workshop steering committee met on 
the morning of the third day to capture and summarize the workshop results and 
determine final priorities of the research needs. The workshop steering committee was 
formed based on the advice of the Dam Safety Research Work Group to include a 
member of the Work Group; Federal, State, and private sectors; academia; and 
Association of State Dam Safety Officials (ASDSO). Table 1 shows the membership of 
the workshop steering committee and assistants. 

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Table 1.Workshop steering committee members 

Contact Info Contact Info Contact Info Person Position 
phone fax email Affiliation 

Kathy Frizell Team Leader 303-445-2144 303-445-6324 kfrizell@do.usbr.gov Reclamation 

Angela Medina Secretary 303-445-2139 303-445-6324 amedina@do.usbr.gov Reclamation 

Nate Snorteland Member 303-445-2395 303-445-6472 nsnorteland@do.usbr.gov 
Reclamation/Denver Dam Safety Representative 

Charles Tate Member 601-634-2120 601-634-4158 Charles.H.Tate@erdc.usace.army.mil USACE/ERDC 

Darrel Temple Member 405-624-4135 ext 226 405-624-4142 darrel.temple@ars.usda.gov ARS/Dam Safety Research Committee/ASDSO 

Dave Campbell Member 610-696-6066 610-696-7771 davec@schnabel-eng.com Consultant/ASDSO 

Eugene Zeizel Program Manager 202-646-3187 202-646-3990 gene.zeizel@dhs.gov FEMA 

Tom Cook Facilitator 303-445-3292 303-445-6475 tcook@do.usbr.gov Reclamations Value Engineering Group 

The steering committee began by defining the workshop topics. Our goal was to define 
two major topics with subtopics that would encompass all aspects of dam spillway issues. 
The following topic areas were determined: 

* Topic 1: Enlargement, modification, and retrofitting of dam service and/or 
emergency spillways including: 
- Labyrinth spillways 
- Fuse plug embankments and fuse gates 
- Crest parapets/dam raising including chutes and dissipaters 
- Gated spillways, both traditional and rubber gates 
- Earthen spillways 
- Dam spillway foundation erosion 
- Dam overtopping technologies with limits of applicability and long-term 
maintenance requirements 

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* Topic 2: Inspection, maintenance, and monitoring required to ensure proper 
performance of dam service and/or emergency spillways. Emphasis will be on 
economical maintenance of the state-of-practice regarding the following types of 
dam spillway structures: 
- Earthen spillways 
- Structural concrete spillways 

The next task was to determine a well-rounded group of presenters and participants that 
were considered experts in the field of spillways. The group decided that a 2-day 
workshop could be conducted if the speakers were limited to 20 and if the second day of 
research needs development was well organized. The goal was to obtain a group of about 
30 people that would provide a broad representation of individuals from the Federal, 
State, private, academia, and owner perspectives. Many participants had a broad 
background of expertise that would allow them to provide input on many research needs 
topics. The workshop had a total of 29 attendees. Of these, there were 14 representatives 
from 4 Federal agencies, 2 representatives from State dam safety agencies, 2 university 
professors, 1 dam owner, and 10 representatives from 7 different consulting agencies. 
Appendix A contains a complete list of speakers and participants. 

Once the speakers had accepted, the workshop agenda was developed with the assistance 
of the facilitator, Tom Cook. The workshop agenda is shown in table 2. The first day 
was dedicated to the presentation of the state-of-practice with research needs outlined by 
each speaker. The second day was devoted to research needs development, voting, 
evaluation, and prioritizing. The speakers had all provided a list of research needs prior 
to the workshop. These research needs were listed on sheets of paper and attached to the 
wall to begin the second day of research needs discussion. All attendees then added 
additional ideas and spent a good deal of time coming to a consensus on how the needs 
should be grouped. Each research need topic was then voted on for difficulty and benefit, 
using a remote keypad with software provided by MH Events. The topics that made the 
cut were then evaluated by the group, using the form provided by the Work Group. 

On the morning of the third day, the steering committee reviewed the results of the 
evaluations and summarized and prioritized the research needs. 

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State-of-Practice 

Documentation of the state-of-practice was the first workshop objective. Per the agenda, 
the presentations were given on the first day of the workshop. Table 3 shows the 
presentations that were given to address the workshop topics with the presentation title, 
presenter, and presenter affiliation. 

To ease the burden on each presenter, only an abstract, the presentation, and a list of 
pertinent references were required by the steering committee. Requiring a peer reviewed 
paper was viewed as too much work and would deter participation. Each presenters 
abstract, with contact information, is given in Appendix B. The presentations are 
compiled in Appendix C. The reference list provided by each speaker appears in 
Appendix D, and it should provide a designer with the information needed to apply the 
technologies presented. 

Table 3.Summary of workshop presentations by title and 
presenter for each major workshop topic 
Presentations Presenters Presenters Affiliation 

TOPIC 1 

Hydraulic Design of Labyrinth Weirs and Fuse Gates Dr. Henry T. Falvey Henry T. Falvey and Associates, Inc. 

Fuse Plug EmbankmentsState of the Art and Practice, and Research Needs 
Tony Wahl Reclamation, Water Resources Research Laboratory 
Crest Parapets and Dam Raising Dwayne Fuller USACE 

Gated Spillways: Enlargement, Modification, and Rehabilitation State of Practice 
Elizabeth Cohen Reclamation, Waterways and Concrete Dams 

Earthen Spillways Design and AnalysisState of the Practice Darrel Temple U.S. Department of Agriculture, ARS 

Spillway Foundation Erosion Jim Ruff Colorado State University 

Dam Overtopping Protection TechnologiesState of Practice and Research Needs 
Kathy Frizell Reclamation, Water Resources Research Laboratory 

RCC Overtopping Protection for Increasing Spillway Capacity Ken Hansen Schnabel Engineering, Inc. 

General DiscussionNRCS Designs and Research Needs James Moore NRCS, National 
Water Management Center 

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Table 3.Summary of workshop presentations by title and 
presenter for each major workshop topic 

Presentations Presenters Presenters Affiliation 
SpillwaysAn Owners Perspective Jim Weldon Denver Water Board 

General DiscussionConsultant's Spillway Design and Research Needs 
Wade Moore MWH Americas, Inc., and Chair, ASCE Hydraulic Structures Committee 

TOPIC 2 

Vegetated Earth Spillways Inspection, Maintenance, and Monitoring Morris Lobrecht NRCS 

Earth SpillwaysState of Practice and Research Needs Greg Hammer Colorado Division of Water Resources, Dam Safety Branch 

Issues and Research Needs Related to Hydraulics for State Regulated Dams 
Ed Fiegle Georgia Department of Natural Resources, 
Safe Dams Program 

Concrete Spillway Repairs Jim McDonald Private Consultant 

Inspection of Concrete Spillways Gated and Uncontrolled Bill Bouley Reclamation, Inspections and Emergency Management 

Geophysics for Spillway and Seepage Evaluation Mark Dunscomb (w/Dave Campbell) Schnabel Engineering, Inc. 

Inspection, Maintenance, and Monitoring of Service and Emergency Spillways 
Dan Johnson MWH Americas, Inc. 

Unlined Spillway Erosion Risk Assessment Joe Koester USACE, Engineering Research and Development Center 

Workshop Presentations 

Each technical expert was asked to prepare a 20-minute-long presentation in their subject 
area that included: 

* A short overview to orient the audience 

* Current activities or the state-of-practice 

* Long- and short-term research issues in your topic area 

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The goal was to provide the entire workshop group the background on the state-ofpractice 
and research needs as viewed by the technical experts, so that the second day of 
the workshop dealing with research needs could be started on an equal footing. 

The following paragraphs give a brief synopsis of the state-of-practice presentations. 

Hydraulic Design of Labyrinth Weirs and Fuse Gates  Henry Falvey 

This presentation focused on two ways to enlarge spillway capacity using the principle of 
increasing the length of the weir crest by folding it into a given width. Labyrinth weir 
technology has been around a long time, but until recently, the hydraulic design criteria 
have not been well established. A fuse gate is a labyrinth weir shape that is formed in 
individual pieces and designed to fail or tip over, lowering the hydraulic control when a 
certain flow depth over the gate is attained. In this way, the fuse gate provides increased 
controlled flow using a labyrinth shape, then a controlled failure down to a given sill 
elevation, to accommodate extreme floodflows. 

Modeling results were presented with recommended design guidance provided for both 
the labyrinth weir and fuse gate. 

Fuse Plug EmbankmentsState of the Art and Practice, and Research Needs  Tony 
Wahl 

This presentation focused on the design concept for fuse plug embankments in spillways 
and the testing that has been conducted. Fuse plug spillways have undergone extensive 
laboratory testing and a full-scale field test that has confirmed the design concepts and 
added to the comfort level for use. The state-of-practice is that many have been 
designed and constructed, but few, if any, have operated. This leaves some uncertainty 
with regard to their ability to function after years of weathering and settlement. 

Crest Parapets and Dam Raising - Dwayne Fuller 

This presentation discussed the recent hydraulic modeling performed by the USACE 
ERDC regarding methods to increase spillway capacities. Three studies were presented 
where several alternatives, including raising the dam to increase storage, were combined 
with spillway modifications to provide successful passage of increased flows. 

Gated Spillways: Enlargement, Modification, and RehabilitationState of Practice - 
Elizabeth Cohen 

This presentation discussed the use of gated spillways to provide increased flow 
capacities in a spillway. The presentation focused on the importance of determining the 
function of the gate and the design data that must be obtained prior to selection of a gate 
type for increased capacity. Gated spillways offer flexibility in function and may be 
operated remotely if needed. There was then a brief presentation of the types of gates 
available and the pros and cons regarding their operation and maintenance. 

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Earthen Spillways: Design and AnalysisState of the Practice  Darrel Temple 

This presentation stressed the state-of-practice for design tools for earthen spillway 
channels. The design goal is to pass the flood without breaching, although damage may 
occur. There are three basic tools for design: 

* Stable exit channel 

* REMR (USACE) Erosion Prediction Method 

* SITES (USDA) Spillway Erosion Analysis 

The presentation focused on the three phases of the erosion process, as dealt with in the 
SITES analysis of vegetation erosion, bare earth or concentrated flow erosion, and 
erosion by headcut advance. 

Spillway Foundation Erosion  James Ruff 

Scour from spillway and outlet jets can cause undermining of chutes and structural 
damage that is expensive to repair. This presentation focused on large-scale testing and 
subsequent development of tools to predict the rate of scour from high-velocity jets 
impacting earth and rock materials below both flip bucket or orifice outlet spillways and 
outlet valves. Colorado State University performed large-scale testing to investigate the 
properties of water jets traveling through the air, pool of water, and impact on 
cohesionless beds and on simulated rock material. The water jets attempted to simulate 
waterflow from orifice outlets, flip buckets, or outlet valves. The objective of the study 
was to investigate the depth and rate of scour caused by the jets on the various foundation 
materials. Results provided a method to calculate scour hole formation and dimensions. 
A brief discussion was presented of spillway rock channel and concrete block protection 
systems for earthen channels that were covered in more detail by another presenter. 

Dam Overtopping Protection TechnologiesState of Practice and Research Needs  
Kathy Frizell 

This presentation focused on providing a very brief synopsis of the technologies available 
to protect embankment dams and earthen spillway channels during flood events that 
would cause overtopping or flow in the channels. Providing protection over the earthen 
slope is often economical compared to other techniques used for spillway enlargement. 
The hydraulics of high-velocity flow over an embankment were discussed. Basic 
guidelines for each technology were given regarding the limitations of their use based 
upon testing, small and large scale, and actual installations. The large-scale testing and 
design guidance developed for riprap and stepped spillways was emphasized. 

RCC Overtopping Protection for Increasing Spillway Capacity  Ken Hansen 

This presentation emphasized the use of RCC to increase spillway capacity by providing 
many examples of actual installations. Each installation provided insight into a 
construction technique or aspect of the placement where lessons were learned and the 
technology was advanced. Basic guidelines for construction and RCC compaction were 

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discussed with the need for understanding the flow forces that the surfaces will be 
subjected to as an important feature. 

General DiscussionNRCS Designs and Research Needs  James Moore 

This presentation focused on the hydrologic events used to design service and auxiliary 
spillways within the NRCS. Hydrologic criteria for auxiliary spillways are determined 
based upon the hazard classification of the dam and are a function of the Probable 
Maximum Precipitation (PMP). Examples of the typical intake tower used by NRCS as a 
service spillway were discussed. Examples of the three most common auxiliary spillway 
designs utilized by NRCS (vegetated earthen, straight drop, and RCC spillways) were 
also shown. 

SpillwaysAn Owners Perspective  Jim Weldon 

This presentation focused on revisiting the issue of the design hydrologic events for 
spillways and the use of the PMP and Probable Maximum Flood (PMF). The current 
practice has been to use the National Weather Service Hydrometeorological Reports 
(HMR) to derive the PMP and then compare spillway capacity to the flood determined 
from the PMP. The presenter contended that while this level of conservatism may be 
appropriate for large Federal facilities, most dam owners, including some Federal owners, 
do not have the funding to comply. The presentation outlined several problems with 
using HMRs. In addition, questions were raised regarding the appropriateness of the zero 
risk approach, inconsistent application from State to State, new computer capability that 
should allow revisiting the procedures, and whether or not a smaller frequency event, 
such as the 5,000-year or 10,000-year storm, would be adequate. 

General DiscussionConsultant's Spillway Design and Research Needs  Wade Moore 

This presentation focused on two organizations that the presenter is affiliated with and 
their spillway design issues. First, the efforts by ASCE to address research, analysis, 
design, construction, operation, and maintenance of state-of-the-art methodology 
associated with hydraulic structures were discussed. The presenter then discussed the 
types of spillway expansion projects that Harza has completed over the last decade. 
Finally, methods to determine dam failure analysis were given. 

Vegetated Earth SpillwaysInspection, Maintenance, and Monitoring 
Morris Lobrecht 

This presentation focused on inspection, maintenance, and monitoring performed by the 
NRCS Fort Worth Office when dealing with earth auxiliary spillways. Many examples 
of well maintained and poorly maintained spillways were shown. The types of the 
problems encountered on the spillways and the expected result of the problems were 
discussed. Several spillways were shown during or after flows had been passed. Steeper 
slopes experienced more damage than flatter slopes when both had good vegetative cover 
and maintenance. 

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Earth SpillwaysState of Practice and Research Needs  Greg Hammer 

This presentation discussed the popularity of using an earth channel spillway because of 
economical design and simple construction. However, these same properties are the basis 
for the limited resistance to hydraulic loading, as is evidenced by eroded channels after 
flows occur. The dilemma for the engineer regarding the design of an earth channel thus 
becomes not only how large the spillway must be to pass a given design flow, but also 
how to keep the channel intact during flow, and how to be sure that the spillway will be 
clear, particularly of snow and ice, when it is needed to pass flow. 

Earth spillway design procedures were discussed, and concern was expressed over what 
the appropriate method is to compute the spillway capacity. The method for controlling 
the flow in the spillway must be recognized, and the appropriate method for design must 
be chosen, such as the broad-crested weir formula, uniform flow conditions using 
Mannings equations, or backwater analysis techniques (HEC-RAS, HEC-2). Spillway 
capacities can be determined to be markedly different, depending on the method of 
computation. Snow and ice buildup was also a particular problem discussed. 

Issues and Research Needs Related to Hydraulics for State Regulated Dams  
Ed Fiegle 

This presentation provided the results of a survey that had been performed by Mr. Fiegle 
regarding hydraulic issues faced by State dam safety representatives. Thirty State dam 
safety representatives responded to the questionnaire that dealt with a wide range of 
hydraulic design issues. The following particular problems were presented as top 
concerns of the State dam safety community: snow and ice, RCC step design and 
durability, siphon spillway design, articulated concrete block system performance, 
understanding of hydraulic coefficients, irregular spillway shape performance, and drop 
structure designs. 

Concrete Spillway Repairs  Jim McDonald 

This presentation focused on the current practice relating to concrete repair techniques in 
spillways. The primary problem with concrete repairs is cracking, due to incompatibility 
between the repair material and the original concrete surface. Results of extensive 
laboratory and field performance testing that now provide a basis for selection and 
specification of dimensionally compatible cement-based repair materials were presented. 
Performance criteria regarding minimum tensile strength and elasticity, shrinkage, and 
thermal expansion were also discussed. 

Inspection of Concrete SpillwaysGated and Uncontrolled  Bill Bouley 

This presentation focused on the important aspects to investigate when performing 
inspections on concrete spillway surfaces. Particular emphasis is placed on visual 
inspection and the importance of a good technical background for the inspector. Many 
examples were given of poor concrete surfaces or poor maintenance leading to potential 
problems during passage of flood events. Emphasis was placed on inspecting when the 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

12 

spillway is in operation or when the reservoir water levels are high. Inspection and 
monitoring techniques include visual above ground, underwater diving and remotely 
operated vehicles, climbing, surveying, crack monitoring and mapping, and nondestructive 
evaluation where the extent of a suspected problem must be known. 
Expensive non-destructive techniques and monitoring with instrumentation must be paid 
for by the dam owner, and it is often difficult to obtain the appropriate services. 

Geophysics for Spillway and Seepage Evaluation  Mark Dunscomb (w/Dave Campbell) 

This presentation outlined the advantages of using geophysical noninvasive and nondestructive 
techniques to characterize subsurface risk on a project. These should be used 
in combination with intrusive methods to improve the understanding of subsurface voids 
or waterflow. Several examples were given to show the capability of geophysical 
techniques and how they can be used to save money by preventing problems before they 
become insurmountable. 

Inspection, Maintenance, and Monitoring of Service and Emergency Spillways  
Dan Johnson 

This presentation focused on what components were necessary to have a successful 
inspection, maintenance, and monitoring team. Development of a successful team begins 
with understanding the owners and publics perception, and relating important historical 
events to the current timeframe. Inspection must include knowledge of the potential 
failure modes. Maintenance is often infrequent and directed primarily at the service 
spillways. Owners must be aware that older structures need attention, but that new 
rehabilitation techniques may not have the redundancy built in that the older, more 
traditional techniques did. Monitoring is vital, but the information gathered must be 
evaluated and is of no use if not reviewed and understood. 

Unlined Spillway Erosion Risk Assessment  Joseph Koester 

This presentation provided a methodology to assess the probability of damage to unlined 
spillway channels and a tool to prioritize remediation of unlined spillway channel 
projects. Risk assessment deals with answering these questions: what can go wrong, 
what is the likelihood it will go wrong, and what are the consequences? Event trees are 
used to assess the issues with probabilistic techniques to produce hard numbers for 
comparisons. An example of how risk assessment techniques are used on an unlined 
spillway channel was presented. 

Summary 

The presentations were all very well received and provided the entire group of 
participants with the topic state-of-practice and each experts thoughts on further research 
needs. The workshop participants each were selected because they had a specific 
expertise; however, each participant also had a broad base of experience that allowed 
them to participate in evaluating research needs in other areas. All workshop participants 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

13 

were instructed to think about other points of research that they felt were important to 
include during the next days research needs session. 

Research Needs 

This section will discuss the research needs developed from the workshop. Each 
presenter provided a list of research needs related to their topic prior to the workshop. 
The workshop organizers compiled the research needs by listing main topic headings on 
large sheets of paper and attaching them to the wall of the room before the second day of 
the workshop. This provided an organized starting point for the development of research 
needs by the entire group on the second day. At the conclusion of the first day of the 
workshop, everyone was encouraged to come early the second day to add their personal 
thoughts on research needs, as all the participants had a broad experience base that 
allowed input on several topics. 

This section does not distinguish between research needs topics provided by the 
presenters or state-of-practice experts and other participants, but it gives all the topics 
developed by the entire group. The presenters specific research needs are given in their 
abstracts or slides (shown in Appendices B and C). The following discussion describes 
how the research need topics were compiled to facilitate overall understanding, grouping 
of like ideas, and voting. 

Topic Development and Discussion 

The initial sheets had main topic headings with research needs topics listed below them. 
There were initially 76 separate topics, if each topic were to stand alone as a research 
need. The group then began the process of rearranging and compiling what were judged 
to be similar topics under main heading categories. During this phase, quite a bit of 
overlap was discovered between topics, and even main topic headings were modified. 
This process was fairly time consuming, but the result was an organized list of main 
headings, each with several topics and related tasks grouped beneath each topic. There 
were finally 10 main headings with 32 topics listed beneath them that were agreed upon 
by the group. Table 4 shows the entire list of topics with letters assigned to the compiled 
topics. These 32 topics were then voted on for difficulty and benefit by the group. The 
compiling process contributed to a certain amount of narrow scope bias in the voting 
because singular topics were generally rated as less difficult to accomplish, whereas 
topics with many tasks were generally rated as more difficult to accomplish (as would be 
expected). Unfortunately, we found no way to successfully amend this process. Topics 
that have numerous tasks generally were of high benefit but were viewed as much more 
difficult to achieve in terms of time and cost. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

Evaluation of Research Needs 

The Dam Safety Research Work Group has published draft guidelines for use in 
evaluating the research needed, as determined by all the workshops that are being 
conducted. They requested that we follow this procedure when developing the results 
from this workshop. The procedure was to vote on difficulty and benefit for each topic, 
then plot the results on a decision quadrant. Worthwhile topics, based upon the Work 
Group criteria, were then evaluated further using the form developed by the Work Group 
and utilized in this workshop. 

Voting 

The next step in the workshop was to vote on the difficulty and benefit for the 32 topics. 
For this purpose, MH Events was contracted to provide remote keypads for assigning a 
difficulty and benefit score from 1 to 10 for each topic. The information was instantly 
recorded and graphed for evaluation of the result. If the result did not look appropriate, 
the facilitator would ask for the topic to be clarified so that perhaps the voting would be 
better distributed. The participants did not see this graph so they were not influenced by 
other opinions. The graphical result from this individual topic voting is shown in 
Appendix E. 

Decision Quadrant 

The ultimate goal of the voting process was to develop the decision quadrant as requested 
by the Dam Safety Research Work Group. A decision quadrant is typically used in these 
types of situations with the axes defined as needed. In this case, the quadrants were 
developed based upon a rating scale of difficulty and benefit as shown in figure 1. 

Based upon the Work Group goals, only those topics that were rated low difficulty/low 
benefit (LD/LB), low difficulty/high benefit (LD/HB), and high difficulty/high benefit 
(HD/HB) would be considered for requests for future research proposals and funding. 
The quadrant of LD/LB is often termed the low hanging fruit, topics that are not of 
high benefit but are easy to accomplish and somewhat useful. These topics may be just 
one remaining task from a larger project or a task that, when completed, could lead to a 
future program or project. The LD/HB quadrant is obviously desirable because the 
results are perceived to have broad application and be very important, whereas low 
difficulty implies that the tasks can be completed with relatively little short-term effort. 
In addition, low difficulty also implies that the tasks should be completed with less 
funding. Therefore, the LD/HB quadrant is termed short term research and would be 
attractive to the Work Group. The HD/HB quadrant is defined as long-term research and 
might require a fairly lengthy and expensive research program to complete; however, the 
benefit is perceived as worth the investment with broad application and essential 
guidelines received from the program. Difficulty/benefit voting was essential to 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

21 

determining whether topics were carried forward for further evaluation by the group and 
possible research funding as per the Work Group directive. 

1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
Low difficulty/High benefit (LD/HB) 
High difficulty/High benefit (HD/HB)
Low difficulty/Low benefit (LD/LB)
High difficulty/Low benefit (HD/LB)
DIFFICULTY

Figure 1.Research needs decision quadrant definition.

Figure 2 shows the result of the voting on all the topics from table 4, including the topic 
letters. Twenty-six topics remained after eliminating topics that clearly fell into the 
HD/LB quadrant. Topics that fell on the dividing lines bounding the HD/LB benefit 
quadrant (topics that would not be carried forward) were then voted on (with a show of 
hands) by the entire group to determine if they would be further evaluated. Topics B, S, 
T, U, AA, and AB fell on the line separating the LD/LB and HD/HB quadrants from the 
HD/LB quadrant that would not be kept for further evaluation. The group voted to keep 
topics T and AB. The final list of research needs topics, as voted by the workshop 
attendees, is shown in the last column of table 4. At the end of the difficulty/benefit 
voting, there were 22 topics left to be evaluated using the form developed by the Work 
Group. 

Evaluation 

Completion of the voting and the results from the decision quadrant led to the evaluation 
phase of the workshop. All the research topics from the decision quadrant, except for 
those in the high difficulty/low benefit quadrant, were retained for evaluation scoring. 
The Dam Safety Research Work Group has developed scoring criteria for evaluating 
research needs identified in the various workshops against three broad evaluation scoring 
areas: value, technical scope, and product. The research evaluation form was forwarded 
to the workshop steering committee to use during this phase of the workshop. Table 5 is 
the research evaluation form that was used by the workshop attendees after a couple of 
minor modifications to the original form forwarded by the Work Group. The workshop 
committee added the research topic title and a section for a brief topic description. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 21 

Figure 2.Decision quadrant results for each topic developed during the
brainstorming session. Each lettered topic is shown in table 4. The blue topics were
not voted on with the evaluation criteria. The topics on the lines between quadrants
were re-voted (by a show of hands) by the group as to whether to retain for further
evaluation. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 22

Table 5.Evaluation criteria for research topics developed by the Dam Safety
Research Work Group. (Note: The form was slightly modified for use by these
workshop participants by adding the research topic title and the brief description.)

Research Topic:

Brief topic description:

Subscore Scoring Area: Subtitle: Criteria (circle one) Evaluator's Score
(transfer circled score)

Value 40

Usefulness 11

Broad federal/state support
in addition support from
NDSP Research workgroup 11

Proposal from any source
addressing a need identified
by the NDSP Research
workgroup 8

Identified need with limited
support
(Federal/State/Academic/Private) 5

Unsolicited proposal with
independent validation 2

Unsolicited proposal 1

Cost 8

Total Project Cost
<$50,000 8

<$100,000 6

<$250,000 4

<$500,000 2

>$500,000 0

Probability of
Success 6

Useful product virtually
certain 6

Identified interim products
for progress and long term
direction 4

Significant technical
challenges to overcome 2

Unlikely to obtain a useful
product 0
	

Table 5.Evaluation criteria for research topics developed by the Dam Safety Research
Work Group (Note: The form was slightly modified for use by these workshop
participants by adding the research topic title and the brief description.) 

Subscore Scoring Area: Subtitle: Criteria (circle one) Evaluator's Score
(transfer circled score)

Transferable to
the Public: 4
(General,
Engineering,
regulators,
Owners)

Proposed format of products meets
needs of sectors 4

Proposed format of products meets
needs of 2-3 sectors 2

Proposed format of products meets
needs of 1 sector 1

No identified transfer of benefits 0

Timeliness 2

Products developed within 1 year 2

Products developed over multiple
years with interim products
identified 1

Products developed over multiple
years with no interim products
identified 0

Leverage 6

Part of NDSP workgroup plan with
>80% cost share or in-kind service 6

Part of NDSP workgroup plan with
>50% cost share or in-kind service 4

Part of NDSP workgroup plan with
all NDSP research funding with
federal or state/ASDSO sponsor 2

All NDSP Research funding 0

Societal Benefits 3

Relevant to current events/societal
concerns (promotes additional
state/federal funding) 3

Promotes general societal
awareness 1

Targeted to specific interests 0

Value total 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 24

Table 5.Evaluation criteria for research topics developed by the Dam Safety Research
Work Group (Note: The form was slightly modified for use by these workshop
participants by adding the research topic title and the brief description.)

Subscore Scoring Area: Subtitle: Criteria (circle one) Evaluator's
Score
(transfer circled score)

Scope 40

Audience 5

General (Lay) 1

State 1

Federal 1

Private 1

Research (future impact) 1

(One point for each group whose
need are addressed)

Facilitate
decisions 6

Does scope include or address:

Facilitation of day to day dam
safety decisions 2

Development, documentation, or
modification of practices 2

Regulatory activities or decisions 2

(Max of 2 points for each issue
covered)

Sound science 12

Is proposed work based on sound
scientific principles:

Is scope and/or product consistent
with resources available or
proposed 4

is data available or to be acquired
to address issue as intended 4

Is data or approach consistent with
quality and nature with identified
end product 4

(Maximum of 4 points for each
issue)

Staff resources 12

Are appropriate staff resources
available?: 12

Recognized experts are PI's

Recognized experts are
collaborators

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 25

Table 5.Evaluation criteria for research topics developed by the Dam Safety Research
Work Group (Note: The form was slightly modified for use by these workshop
participants by adding the research topic title and the brief description.)

Subscore Scoring Area: Subtitle: Criteria (circle one) Evaluator's Score (transfer circled score)

PI's are new to area

Primarily new scientists or
grad students

No qualified technical staff 0

(Rated 0 to 12 based on
appropriateness of available
staff)

Scope total

Product 25

Output 15

Produce a process, tool, or
technique (guideline,
computer program, equation,
etc)? 15

State of
technology 3

Define or summarize an
entire state of technology or
practice for a dam safety
audience 3

Safety lessons 2

Extract important dam safety
lessons from case histories 2
Innovative
technology 2

Produce product with new,
novel, or innovative
technology 2

Tech Transfer 3

Develop products or
technology that can be easily
transferred for use by dam
safety interests 3

Product
Total

Research topic total*

*Sum of all scoring areas.

26 FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways

On the evaluation form, each main evaluation scoring area has several subtitles or 
subcategories with possible scores designated. The value scoring area has seven 
subcategories, with usefulness and cost having the most importance or the highest point 
values. The scope scoring area has four subcategories, with sound science and staff 
resources having the highest point value. The product scoring area has five subcategories 
with the final output far outweighing the others in point value. A total score of 100 is 
possible (value = 40 points, scope = 35 points, and product = 25 points). The 
understanding of these categories and their weighted importance played a role in the 
group topic scoring. 

To perform the evaluations, the workshop participants were divided into small groups of 
four or five people, with an effort to blend Federal, private consultants, State, and 
academia in each group. The facilitator then went around the room and asked each group 
which topic they would like to evaluate until all the topics were selected. Each small 
group evaluated three to four topics. Instructions were then given to the groups regarding 
the value, scope, and product scoring areas and how to fill out the form. It was beneficial 
to have Darrel Temple, from the Work Group, at the workshop to provide an overview of 
the thinking behind the form and to answer questions. Each small group then completed 
their evaluation forms for each of their topics. The evaluation forms for each topic are 
attached in Appendix F of this report. 

The end result is a scoring document for identifying valuable and cost-effective research 
needs to be addressed in the 5-year strategic plan. As additional research needs are 
identified from other sources, they can be prioritized and included in the priority listing. 
The scoring system will enable the National Dam Safety Program to move research 
forward to produce easily developed, timely, and useful products in the near-term and to 
develop more difficult, but useful, research over the 5-year timeframe. It also will be 
possible to revisit research each year and to revise priorities based on current needs and 
knowledge gained from ongoing research and other developments. 

Results 

Twenty-two topics were evaluated using the form provided, after eliminating the HD/LB 
topics using the decision quadrant tool. The evaluation sheets were gathered after the 
groups completed them. After a short break that allowed the workshop facilitator to 
compile the evaluation scores, the workshop members were told which topics had the 
highest evaluation scores. Table 6 and figure 3 show the compiled results of the 
difficulty/benefit voting and the evaluation scores. All the numeric values are shown 
together in table 6 so that the highest scoring topics and their relationship to the 
difficulty/benefit rankings can easily be seen. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 27

Table 6.Tabulated results of the difficulty/benefit voting 
and the group evaluations for each research topic 
(See table 4 for the topic title that matches the topic letter.) 

Topic Letter Difficulty Benefit Evaluation Score 
C 4.3 5.2 75 
D 4.1 5.5 79 
E 2.9 5.2 85 
F 7.9 6.1 60 
G 5.8 6 76 
H 6.4 8.3 94 
I 6.8 8.4 81 
K 4.6 4 36 
L 7.8 8.6 80 
M 4.5 7.4 89 
N 4 6.8 72 
- 4.8 3.2 55 
R 6.8 7.8 79 
T 6.2 5.6 64 
V 4.9 5.4 82 
W 4.5 4.8 81 
X 5 5.7 88 
Z 7.4 8.1 85 
AB 6.4 5.5 76 
AC 5.8 6.5 84 
AE 4.2 5.3 68 
AF 3.8 6.1 88 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 28

Difficulty
Difficulty 
1 2 3 4 5 6 7 8 9 10 
Benefit 
1
2
3
4
5
6
7
8
9 
10 
C,75 
D,79 
E,85 
F,60 G,76 
H,94 
I,81 
K,36 
L,80 
M,89 
N,72 
O,55 
R,79 
T,64 
V,82 
W,81 
X,88 
Z,85 
AB,76 
AC,84 
AE,68 
AF,88 

Figure 3.Results of the evaluation ratings for each topic shown on the decision
quadrant for reference. The labels are the topic identifying letter and the evaluation
scores developed by the small groups (i.e. H,94 is topic H with a score of 94).

As a wrapup to the workshop, the evaluation scores were discussed in relation to the topic 
placement within the decision quadrant. A hard copy of the decision quadrant had been 
distributed to the group and evaluation scores could be jotted down as they were read by 
the facilitator. Figure 3 shows the positioning of each lettered topic on the decision 
quadrant, and the evaluation score is listed next to the lettered topic. 

The importance of the three evaluation factors (value, scope, and product) can be seen on 
figure 3. In theory, a high-value project with a well-defined scope and useful product 
would produce the highest priority project. Because the evaluation contained cost 
estimates, if the proposed research topic had a high cost, which generally occurred when 
physical modeling was thought to be required, the value score could be significantly 
lower. Therefore, the most beneficial topic in each quadrant did not always have the 
highest evaluation score. Thus, some of the evaluation rankings in the HD/HB, or longterm 
research area, did not score as high as they potentially might have. 

In a brief discussion of the results, the group felt that, in general, the evaluation scores 
did not contradict the difficulty/benefit results. When asked about the usefulness or 
applicability of the form, the general comments from the workshop participants regarding 
the evaluation form were: 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 29

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 
30 

* The evaluation elements were, in general, easy to understand and fair. 

* Funding was, at most, a best guess. Most workshop participants did not feel 
comfortable putting down a dollar figure for topics if the program was viewed as 
complex. 
- For some topics, if program cost was ranked as high, then the overall topic 
score was low, even though the group evaluating it felt that it was an 
important topic (i.e., Topic E had a relatively low cost at $75,000 and 
obtained a high total evaluation score; topic N had relatively high cost at 
$250,000 and obtained a lower total evaluation score; even though the 
group felt that topic N was perhaps more valuable technically). 

* It was difficult to determine the amount of leverage that would be provided under 
the value scoring area. 

* It was difficult to determine whether or not staff resources would be available 
under the scope scoring area. 

The group also felt that State Dam Safety opinions were lacking, based upon not enough 
representation from the State dam safety community. In general, this was felt to be due 
to a lack of funding for travel for State representatives, not due to a lack of interest. 

Final Prioritization of Research Needs 

The steering committee convened the day after the workshop to discuss the workshop 
process and findings. The committee reviewed the decision quadrant results with the 
rankings from the evaluation criteria. The Dam Safety Research Work Group will not be 
interested in funding the LB/HD quadrant topics at this time. Therefore, those topics were 
not evaluated by the group and not considered in the final prioritization conducted by the 
steering committee. 

The steering committee initially agreed that we should prioritize and forward what we 
considered the top 10 research topics from the workshop results to the Work Group. 
After further consideration, we agreed to use the information shown in the decision 
quadrant (shown in figure 3) developed from the workshop results. It seemed logical to 
take 4 topics from the HD/HB quadrant, 4 topics from the LD/HB quadrant, and 3 topics 
from the LD/LB quadrant for a total of 11 topics. The highest scoring topics from the 
three quadrants were then selected by consensus of the committee and are shown in 
figure 4 and listed in table 7 in descending order, based upon the highest evaluation 
score. 

The steering committee debated what other factors could be used to prioritize the topics, 
and cost seemed to be an important factor. The cost of doing the research was also added 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 30
 
to table 7 from the evaluation sheets because the cost played a role in the evaluation 
process and in the selection of the highest priority research by the steering committee. 
The steering committee also thought that the cost of the proposed research would play an 
important role in determining whether or not the Work Group would fund the 
recommended research. The bar chart in figure 5 shows the cost of the recommended 
research topics from table 7. 

Difficulty 
1 2 3 4 5 6 7 8 9 10 
Benefit 
1
2
3
4
5
6
7
8
9 
10 
D,79 
E,85 
H,94I,81 
M,89
V,82 
W,81
X,88 
Z,85 
AC,84 
AF,88 

Figure 4.Final research needs prioritization from steering committee 
recommendations, based upon the decision quadrant location and evaluation 
scores developed by the workshop participants. 

Overall, the highest priority research topic is topic H, verifying the structural design and 
integrity of RCC embankment dam overlays. This topic had the highest evaluation score 
and the third highest benefit of all the topics. Topic H is in the HD/HB (or long-term) 
research category. In addition to the benefit and evaluation, the cost to perform the 
research outlined in topic H was far less than the others (Z, AC, I) in the long-term 
(HD/HB) quadrant, making it a logical choice. 

Topic M, developing hydraulic design guidelines for embankment stepped spillways, had 
the highest evaluation score and the highest benefit in the LD/HB quadrant. This is 
probably because it is also the lowest cost of the four topics recommended from that 
quadrant. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 31

Table 7.Prioritized research needs topics developed by the workshop steering 
committee from the workshop results 

Topic Letter Ranking Topic Title Difficulty Benefit Evaluation Score Cost $1,000 

H 1 Develop RCC design document  structural aspects 6.4 8.3 94 100 

M 2 Document hydraulic design criteria for embankment stepped spillways 4.5 7.4 89 100 

AF 3 Develop procedures to perform better geophysical exploration of foundation 
voids and seepage 3.8 6.1 88 50 

X 4 Determine criteria for sill wall spacing and foundation needs in earthen 
spillways 5.0 5.7 88 100 

E 5 Develop a design manual for rock 
spillway chutes or steep riprap slopes 2.9 5.2 85 75 

Z 6 Update or develop computer models to 
replace HMR and possibly PMF design 
requirements 7.4 8.1 85 250 

AC 7 
Investigate tools to reduce O&M costs 
and extend life of infrastructure (i.e., 
repairs or inspections) 
5.8 6.5 84 500 

V 8 Research grass design criteria for cool 
weather grass and reinforced grass 4.9 5.1 82 500 

W 9 Determine best method for determining 
earth spillway crest discharge 
coefficients 
4.5 4.8 81 50 

I 10 Develop design guidelines for 
alternative materials for small 
embankment dam overlays 
6.8 8.4 81 1,000 

D 11 Develop design guidelines for siphon 
spillways 4.1 5.5 79 250 

High difficulty/high benefit quadrant 

Low difficulty/high benefit quadrant 

Low difficulty/low benefit quadrant 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 33 

Figure 5.Cost of the recommended research topics from the workshop. 

Topic E, developing a design manual for rock spillway chutes or flow over riprap slopes, 
had the highest evaluation and the lowest difficulty among the three topics recommended 
from the LD/LB (or low hanging fruit) quadrant. The benefit of the three topics selected 
was very similar, and the evaluators felt that minimal effort would be involved with 
documenting existing research to produce a valuable output. 

These three topics are the highest priority for each of the individual quadrants in the 
decision quadrant, and each topic had the highest evaluation score based upon the 
workshop rankings. 

The steering committee generally concluded that technical merit and cost were the most 
important qualities of any research topic or proposal. The committee felt that the 
evaluations aligned with the intuitive feelings of importance by the group in that high 
benefit was not given to topics of relatively narrow usefulness. However, there was a 
bias introduced when several similar topics were combined under a research topic 
heading that generally produced a highly beneficial, but expensive, topic. An example of 
this is topic I, developing design guidelines for alternative protective materials during 
overtopping of small embankment dams. This topic was recommended by the steering 
committee as a worthwhile project, but because this research will most likely involve 
some modeling using many materials, the cost will most likely be high to complete the 
entire program. In contrast, if each individual protective material had been rated 
separately, then the topic most likely would be less costly and even possibly moved to 
another quadrant or given a higher quadrant rating in the current quadrant. 

FEMA Workshop - Issues, Remedies, and Research Needs Relating to Service and/or Emergency Spillways 

34 

The steering committee agreed that cost played a fairly major role in the total evaluation 
scores and it was, therefore, listed separately in the final table of prioritized research 
topics. 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

A-1 

Appendix A 

Workshop Attendees 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 
A-2 

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FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

A-3 

Name Address Phone E-mail 

Kathy Frizell USBR P.O. Box 25007 Denver, Co 80225 303.445.2144 kfrizell@do.usbr.gov 

Jim Ruff 1117 Greenbrair Dr. Fort Collins, CO 80524 970.493.2974 wruff@frii.com 

Greg Hammer 810 9th St., #200 Greeley, CO 80631 970.352.8717 greg.hammer@state.co.us 

Wade Moore MWH 175 W. Jackson Blvd. Chicago, Il 60604 312.831.3098 wade.p.moore@mwhglogbal.com 

Bitsy Cohen USBR P.O. Box 25007 Denver, Co 80225 303.445.3247 bcohen@do.usbr.gov 

Dan Mahoney FERC Division of Dam Safety 888 N. Capitol Street Washington D.C. 
24061 202.502.6743 daniel.mahoney@ferc.gov 

Carlton D. Smith USBR P.O. Box 25007 Denver, Co 80225 303.445.3303 csmith@do.usbr.gov 

Hank Falvey P.O. Box 4 Conifer, CO 80433 303.838.4920 falvey@members.asce.org 

Dan Johnson 370 Interlocken Blvd. Broomfield, CO 80021 
303.410.4189 daniel.johnson@mwhglobal.com 

Sal Todero 8181 East Tufts Denver, CO 80237 303.740.2685 salvatore_toodaro@urscorp.com 

Jim Weldon 1600 W. 12th Ave. Denver, CO 80204 303.628.6657 dames.weldon@denverwater.org 

Dwayne Fuller 3909 Halls Ferry Rd. Vicksburg, MS 39180 601.634.2668 fullerb@wes.army.mil 

Jim McDonald 1414 Huntcliff Way Clinton, MS 39056 601.924.5955 jmcdonald10@jam.rr.com 

Morris N. Lobrecht P.O. Box 6567 Fort Worth, TX 76115 817.509.3775 morris.lobrecht@ftw.arcs.usda.gov 

James Moore 101 E. Capitol, Suite B-100 Little Rock, AR 72201 
501.210.8922 james.moore@ar.usda.gov 

Chuck Tate 3909 Halls Ferry Rd. Vicksburg, MS 39180 601.634.2120 Charles.H.Tate@erdc.usace.army.mil 

Brent Mefford USBR P.O. Box 25007 Denver, Co 80225 
303.445.2149 bmefford@do.usbr.gov 

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Name Address Phone E-mail 
Derek Dice Armortec 4301 Industrial Drive Bowling Green, KY 42101 
800.305.0523 ddice@armortec.com 

Bruce Savage McNeese State University Department of Engineering/Drew Hall 
Lake Charles, La 70609 337.475.5869 BSAVAGE@McNeese.edu 

John Rutledge Freese & Nichols 4055 International Plaza St. 200 Fort 
Worth, TX 76109 817.735.7284 jlr@freese.com 

Nate Snorteland USBR P.O. Box 25007 Denver, Co 80225 303.445.2395 nsnorteland@do.usbr.gov 

Bill Bouley USBR P.O. Box 25007 Denver, Co 80225 303.445.2754 wbouley@do.usbr.gov 

Joe Koester Ceerd-GS-E 3909 Halls Ferry Road Vicksburg, MS 39180-6199 
601.634.2202 Joseph.P.Koester@erdc.usace.army.mil 

Dave Campbell Schnabel Engineering 510 E. Gay Street West Chester, PA 19380 
610.696.6066 davec@schnabel-eng.com 

Tony Wahl USBR P.O. Box 25007 Denver, Co 80225 303.445.2155 twahl@do.usbr.gov 

Ken Hansen 6970 S. Holly Circle, #206, Englewood, CO 80112 
720.482.9103 khansen@schnabel-eng.com 

Chris Veesaert USBR P.O. Box 25007 Denver, Co 80225 303.445.2742 cveesaert@do.usbr.gov 

Ed Fiegle 4244 International Parkway Suite 110 Atlanta, GA 30354 
404.362.2678 ed_fiegle@dnr.state.ga.us 

Darrell Temple USDA, ARS 1301 N. Western Stillwater, OK 74075 405.624.4135 
x226 Darrel.Temple@ars.usda.gov 

Gene Zeizel US Department of Homeland Security-FEMA 500 C Street, S.W. 
Washington, D.C 20472 202.646.2802 Gene.Zeizel@dhs.gov 

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Appendix B 

Abstracts 

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Hydraulic Design of Labyrinth Weirs and Fusegates 

Henry T. Falvey 1 

Most spillways consist of some form of a weir. The weirs are normally placed 
perpendicular to the flow direction. The most significant parameters in determining the 
capacity of a weir are its height relative to the upstream depth, the crest shape, and the 
crest length. Here, capacity refers to the flow rate or discharge for a given depth of flow 
over the crest of the weir. Of these parameters, the crest length has the greatest influence 
on the spillway capacity. 

As the emphasis in dam safety has increased, many spillways must be rehabilitated to 
increase their capacity without changing the reservoir storage. However, for many 
spillways, the width of the approach channel or the downstream chute cannot be widened. 
To increase the crest length but keep the spillway width constant, the crest is often placed 
at an angle to the centerline of the chute. The length can be increased further and can still 
keep the downstream dimension constant by folding the weir into several sections. These 
sections can be rectangular, triangular, or something in between. 

The key points are 

* Increased spillway capacity 

* Research needed for crest shape, interference, splitters, approach 
flow conditions and raised invert. 

* Preliminary design hydraulics and economics can be estimated 
easily with available computational methods. 

* Model tests of specific installation recommended. 

Fusegates are a proprietary device that is sold by Hydroplus in France. Lemprire 
invented them as a method of increasing spillway capacity or reservoir storage. They 
consist of a series of metal or concrete gates that when placed together have the shape of 
a labyrinth weir. As the flood rises, the gates tip as a function of the reservoir level. 

The base of the each gate contains a block-out that fills with water when the reservoir 
rises above a specified elevation in a well. The well is located on either the gate or on the 
sidewalls of the spillway chute. When the block-out fills, the water pressure in the space 
creates an overturning moment that causes the gate to tip. The flowing water washes the 
gate downstream. 

Research has been conducted on the effects of waves, downstream blockage, and ice on 
the performance of the gates. The key points of the fusegates are: 

* Used to increase spillway capacity 

* Used to increase reservoir storage 

* Extremely predictable tipping as a function of reservoir elevation 

1 Dr. Henry (Hank) T. Falvey, President, Henry T. Falvey & Associates, Inc., Mail: P.O. Box 4, Ship: 
11624 Blackfoot Rd., Conifer, CO 80433, phone & fax: 303- 838-4920, falvey@members.ASCE.org 

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* Ice loadings, waves, seismic, and downstream plugging of stream have been 
studied 

* Model studies of specific installations is required 

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Fuse Plug Embankments  State of the Art and Practice, and Research Needs 

Tony L. Wahl 2 

The state of the art in fuse plug embankments is the design concept first described by 
Tinney and Hsu (1961). This approach utilized an inclined clay core underlain by a noncohesive 
shell material. When the shell material is eroded away, the core fails as a 
cantilevered structural element, leading to rapid, reliable breach initiation. Laboratory 
and field testing by Tinney and Hsu and later testing by the Bureau of Reclamation 
(Pugh, 1985) confirmed acceptable performance and provided a means for estimating the 
lateral erosion rate of an embankment. Since the completion of the tests by Pugh, 
Reclamation has constructed four spillways with fuse plug embankments. None of these 
spillways has operated. Application of fuse plug embankments outside of Reclamation is 
thought to be relatively widespread on small dams, but there has been no comprehensive 
investigation. Many small dams are believed to be equipped with so-called fuse plug 
embankments that do not incorporate the design features described by Tinney and Hsu. 
Documented operational experience is extremely limited. During May of 2003 a fuse 
plug embankment operated in northern Michigan, causing damaging floods on the Dead 
River. Erosion of this embankment apparently continued to a deeper elevation than 
intended. 

Three primary research needs are identified. First, long term performance of the thin clay 
core has been a concern on many projects. Cracking due to dessication and/or 
differential settlement and maintaining good contact between the core and 
floor/abutments are issues. Some have proposed use of alternative materials to address 
these issues, so a second research need is for development of designs that use 
impermeable goetextiles or concrete core walls designed to fail in a controlled manner. 
Finally, an inventory of fuse plug spillways is needed, so that the performance of 
different past and future design concepts can be evaluated. 

2 Tony Wahl, MS, PE, Hydraulic Engineer, US Department of Interior, Bureau of Reclamation, Technical 
Service Center, Water Resources Research Laboratory, P.O. Box 25007, D-8560, Denver, CO 80225, 
phone: 303-445-2155, twahl@do.usbr.gov 

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Crest Parapets and Dam Raising 

Dwayne Fuller 3 

In 1956, the National Weather Service (NWS) published generalized estimates of 
probable maximum precipitation (PMP) for areas of the United States east of the 105th 
meridian in Hydrometeorological Report (HMR) no. 33. Later, at the request of the U.S. 
Army Corps of Engineers, the NWS published HMR No. 51, dated June 1978, which 
revised and expanded PMP estimates. The dam safety assurance analysis used HMR No. 
51 to derive the probable maximum flood (PMF) and subsequent hydrologic deficiencies 
of several dams. Two of these dams were Tygart Dam near Grafton, West Virginia and 
Bluestone Dam near Hinton, West Virginia. 

Because of hydrologic deficiencies these dams would not safely pass the PMF. This 
presentation discusses the model studies used to evaluate alternative actions or designs 
for remediation of these deficiencies. 

3 Dwayne Fuller, Hydraulic Engineer, U.S. Army Corps of Engineers, Engineer Research and 
Development Center, Coastal and Hydraulics Laboratory, Inland Hydraulic Structures Branch, Structures 
and Channels Group, 3909 Halls Ferry Rd. Vicksburg, MS 39180, phone: 601-634-2668, 
fullerb@wes.army.mil 

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Gated Spillways - Enlargement, Modification and Rehabilitation - 
State of the Practice 

Elizabeth Cohen 4 

The design of a dam with gates provides greater flexibility in the operation and 
management but also require specific operation and maintenance plans while posing 
potential risks due to mis-operation. The design of a gated spillway should address the 
function and needs of the project. A dam with a gated spillway operates to its full 
potential capacity only when the gates are open to discharge floods. Gate failures are not 
an uncommon phenomenon whether due to structural, power supply interruption or 
general miss-operation. If any gate fails to open during a flood, the safety of the whole 
dam is at risk. If any gate opens in error during normal operation, the artificial flood 
generated may endanger life & property downstream. Reclamation requires that any 
redesign or modification be a risk neutral design or that the risks do not increase for the 
downstream population. 

The determination of function and needs should involve an evaluation of high head vs. 
low head, river flow, potential for storage of large floods (>100 Yr), maintenance, and 
attendance issues. The design and data should evaluate and address the river flow 
(normal, minimum, maximum, or bypass needs), storm storage, climatic conditions 
(temperature changes, winter conditions), reservoir fluctuations, vandalism, security 
issues, debris, controls and automation - operate remotely or onsite, emergency power, 
and flow measuring capability. 

The types of gates available for consideration include Slide Gate, Wheel Gate, Radial 
Gate (or Tainter Gate), Drum Gate, Crest Gate (i.e. Obermeyer Gate or Rubber Dam), 
Fusegate, and Flashboards. Additional research needs could address development of 
information for the discharge; submergence effects on discharge, extrapolations to other 
situations, flows released during failure, seismic and security modifications, cost, 
maintenance, and durability. Other areas to be addressed may include air supply 
downstream of gates, orifice properties of submerged gates, transitions from open 
channel flow to submerged gates, discharge coefficients, and degree of accuracy of flow 
at rubber dams. 

4 Elisabeth Cohen, MS, PE, Civil Engineer, US Department of Interior, Bureau of Reclamation, Technical 
Service Center, Waterways and Concrete Dams Group, P.O. Box 25007,. D-8130, Denver, CO 80225, 
phone: 303-445-3247, bcohen@do.usbr.gov 

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Earthen Spillways Design and Analysis  State of Practice 

Darrel Temple 5 

Earth channels have been widely used for auxiliary or emergency spillways to convey 
major flood flows around dams. These spillways are normally designed to flow 
infrequently and are generally considered have operated successfully if erosion 
experienced during a given event does not threaten the integrity of the dam and reservoir. 
For watershed flood control reservoirs, the typical earth spillway consists of a vegetated 
channel with an inlet reach, a level crest section, and one or more exit channel reaches 
designed to flow supercritical at design discharge. Larger structures may incorporate 
concrete weirs or sills to provide improved hydraulic control characteristics, including 
more uniform flow conditions over the width of the spillway. Energy dissipaters and 
erosion barriers of various forms may also be integrated into the design, but this 
discussion focuses on the behavior of the earth spillway channel itself. 

Historically, earth or vegetated earth spillways designs were based on stable channel 
design criteria described in publications such as the USACE Hydraulic Design of Flood 
Control Channels or on an empirical bulk length as described in USDA TR-52. 
Although failure of these spillways has been rare, erosion observed during spillway flows 
has led to refinement of design and analysis procedures in recent years. The United 
States Society on Dams is presently developing a bulletin describing the history and the 
present state of the science in the area of erosion of earth spillways in more detail. 
Publication of this bulletin is expected during 2004. 

The methods presently being used for the design and analysis of earth spillways tend to 
be semi-empirical, based on flows and erosion observed during the past 25 years. The 
REMR erosion prediction method developed by the US Army Corps of Engineers 
consists of a classification system that allows comparison of an erosion risk class with an 
erosion potential class. The approach predicts whether erosion is or is not expected. 

The vegetated earth spillway erosion model developed by USDA and incorporated into 
the NRCS Sites software divides the erosion process into three sequential phases: 1) 
failure of the vegetal cover, if any, and development of concentrated flow; 2) surface 
detachment in the area of concentrated flow leading to development of a vertical or near 
vertical headcut; and 3) deepening and upstream advance of the headcut. Each phase of 
the process is described by different threshold-rate relations reflecting the physics of that 
phase. The model is applied iteratively to various potential points of initiation to 
determine the scenario with the greatest potential for spillway breach. 

The USDA model represents a first attempt at quantification of the dominant spillway 
erosion processes. The potential exists for refinement of the relations describing all 
phases of the overall process. The US Army Corps of Engineers has applied the general 
approach with modified equations and ongoing research is expected to result in improved 
relations describing the processes. Research is also underway to refine the three-phase 

5 Darrel Temple, Research Leader, Hydraulic Engineering Research Unit, US Department of Agriculture, 
Agricultural Resource Service, 1301 N. Western, Stillwater, OK 74075, phone: 405-624-4135 X226, 
Darrel.Temple@ars.usda.gov 

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approach for application to prediction of dam breach due to overtopping flows. There is 
a need for continued study to develop improved parameters for describing the resistance 
of geologic materials to erosion and for improved means of identifying pertinent 
characteristics of materials that may be exposed during the erosion process. Other 
identified research needs include expanding the current breach prediction model to 
include spillway erosion that occurs after the initial breach and identification of 
conditions where modes of failure other than headcut formation and advance dominate 
the process. 

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Spillway Foundation Erosion 

James F. Ruff, Ph. D., P.E.6 

Spillways consist of control, conveyance, and terminal structures. There is not a high 
incidence of damage or of catastrophic failure of dams or of spillways as a result of 
spillway foundation erosion. The primary reasons are because spillways are constructed 
mainly on abutments, are founded on and anchored to rock, and have drainage systems. 
However, scour can occur downstream from chutes and stilling basins discharging to 
earth or rock exit channels or in plunge pools and basins impacted by water jets from flip 
buckets, orifice spillways, or outlet valves. Undermining of concrete chutes and floor 
slabs can cause structural damage that results in more foundation erosion and/or 
undermining and the cycle can continue. Foundation erosion of one of the components 
affects operation of the structure and of the reservoir and forces repairs under time 
constraints at high costs. 

Changes in design flood criteria have resulted in spillways with inadequate discharge 
capacity requiring different solutions for spillway improvements and enlargements. Most 
research has assumed the foundation was satisfactory and has focused on performance of 
the spillway components using small-scale models. 

At Gibson Dam on the Sun River in Montana, flow over the dam eroded rock at the 
foundation and in the downstream channel in 1964. Although spillway failures have not 
caused catastrophic failures of dams, repairs have been expensive and have affected dam 
operations. 

Testing of innovative methods to protect downstream slopes of earth embankments, earth 
spillways, and terminal channels began at Colorado State University in 1990 when the 
Bureau of Reclamation contracted with Colorado State University to conduct large-scale 
tests of riprap and Reclamation designed concrete wedge blocks. These tests indicated 
the blocks were a viable covering for embankment slopes and provided design criteria for 
riprap on slopes as great as 2:1 (H:V). 

In 1995, Colorado State University began a second series of large-scale tests for 
Reclamation relating to water jets impacting on cohesionless beds and on simulated 
rocks. The water jets attempt to simulate water flow from orifice outlets, flip buckets or 
outlet valves. The objective of the study was to investigate the depth and rate of scour 
caused by the jets. Results provided a method to calculate scour hole dimensions. 

Additional research is needed to investigate: 

* riprap performance for different slopes at near- prototype scale 

* mechanism of rock erosion because of overtopping flow and plunging jets 

6 James F. Ruff, PhD, PE, consultant and retired professor, Colorado State University, 
1117 Greenbrier Dr., Fort Collins, CO 80524, phone: 970-493-2974, wruff@frii.com 

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* evolution of jet velocity and air concentration at surface and within plunge pool 

* jet entry on plunge pool performance and scour 

Prototype data is needed to improve scour prediction formulas. 

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Dam Overtopping Protection Technologies  State of Practice and Research Needs 

Kathy Frizell 7 

Thousands of embankment dams across the US could be severely damaged or fail due to 
overtopping events predicted by increases in design flood amounts. Many embankment 
dam projects must then ensure the existing embankment would survive the flood, enlarge 
an existing spillway, add an adjacent spillway, or allow overtopping of the dam and 
provide protection. Often protecting the dam and allowing overtopping is the most 
economical solution; however, confidence in the protective system must be high. 

Of primary importance when selecting an embankment dam overtopping protection 
method is the durability of the material that is chosen for the hydraulic loading conditions 
that are expected. Many technologies are available. Some have been adequately tested 
and proven to work in the field. Others have been tested and installed in the field, but not 
yet had flows to prove whether or not the method will work. Others have not been tested 
adequately under the high velocity, steeply sloped flow regime that exists on an 
embankment dam and should not be utilized until adequate testing has been performed. 
Some methods have been adequately tested, but not applied on a real dam. 

This presentation will outline the available techniques that are available for use in 
protecting embankment dams during overtopping events: 

* Earthen embankments, grass-covered earthen embankments, geotextiles and 
membranes, gabion or Reno mattresses, riprap, concrete blocks (cable-tied, 
interlocking, overlapping), soil cement, reinforced smooth concrete slab, RCC 
(formed or not) or reinforced conventional concrete formed into steps. 

Each is dependent upon knowledge of the flow hydraulics or forces that act on the 
protection system and the underlying embankment for the given flood event. Basic 
guidelines for each overtopping protection method will be reviewed to give dam owners 
the current state-of-the-practice and research so that they can choose a reliable protection 
system based upon the loading requirements of the flow that must be passed. Examples 
of site specific applications are given when available. 

Research needs mostly are left to documenting the current research on stepped spillway 
design for embankment dams. Then expanding the knowledge of energy dissipation of 
small dams under high flow discharges where the expected rate of energy dissipation is 
probably less than may currently be expected. All technologies need to have flow events 
occur over field installations to improve the acceptability and reliability of the methods. 

7 Kathy Frizell, Hydraulic Engineer, US Department of Interior, Bureau of Reclamation, Technical Service 
Center, Water Resources Research Laboratory, P.O. Box 25007, D-8560, Denver, CO 80225, phone: 303- 445-2144, kfrizell@do.usbr.gov 

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RCC Overtopping Protection for Increasing Spillway Capacity 

By Kenneth D. Hansen, P.E.8 

The use of roller-compacted concrete (RCC) to increase the spillway capacity and thus, 
the hydraulic safety of existing dams is now more than two decades old. In that time, 
RCC has gained the widest acceptance of all the methods available to design engineers 
for providing overtopping protection for embankment dams. The number of dams that 
have been upgraded with RCC overlays now exceeds 80 projects in the USA. The main 
reasons for this widespread acceptance is that an RCC overlay is easily designed, easily 
and rapidly constructed, has a relatively low cost and has had a very good performance 
record in the cases where flows have overtopped the RCC. In addition, all this remedial 
work can be accomplished without lowering the reservoir. 

There is no accepted method for determining the minimum thickness of the overlay 
consistent with the maximum head of water flowing over the RCC. The minimum RCC 
thickness has been based on construction equipment considerations rather than any 
mathematical calculations. In order to place the RCC in 1-ft. thick, horizontal lifts in 
stair-step fashion up the embankment slope, a minimum layer width of about 9 feet has 
been found to work well from both a construction and stability standpoint. For a 3H:1V 
downstream slope, the minimum thickness thus produced is about 1.9 feet. 

Projects in service have shown no hydraulic or structural problems when designed as 
noted above. The biggest problem noted over the years has been due to weathering of the 
outer exposed edges. Deterioration of the RCC surface has been noted in areas subject to 
many freeze-thaw cycles. This situation has been improved upon with greater strength 
RCC mixes (higher cement content) and by greater compaction of the outer edges of the 
RCC. 

Recently, many RCC overtopping protections have been designed with 1 to 2-ft. deep, 
formed steps. The steps are visually attractive, hydraulically efficient and the forms 
provide a means for increasing the compaction at the outer edge. The hydraulic 
efficiency of steps for embankment slopes has not received as much laboratory study as 
those for the steeper gravity dam slopes. Additional research could be accomplished on 
this subject as well as the hydraulic efficiency of steps that have deteriorated a little due 
to weathering. 

8 Kenneth D. Hansen, Principal, Schnabel Engineering, Inc., 6970 S. Holly Cir. #206, Englewood, CO 
80112, Phone: 720-482-9103, Fax: 720-529-5335, khansen@schnabel-eng.com 

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General discussion - NRCS Designs and Research Needs 

Jimmy Moore 9 

The presentation presents the hydrologic criteria used by the Natural Resources 
Conservation Service (NRCS) for the design of principal and auxiliary spillways. It 
includes the storage criteria to determine the crest elevation of the auxiliary spillway and 
the freeboard hydrologic criteria to determine the top of the embankment. Examples of 
various spillways constructed by NRCS are included in the presentation. 

9 James N. Moore Sr., PE, Civil Engineer, United States Department of Agriculture, Natural Resources 
Conservation Service (NRCS), National Water Management Center, 101 East Capitol, Suite B-100, Little 
Rock, AR 72201, phone: 501-210-8922, james.moore@ar.usda.gov 

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Spillways  An Owners Perspective 

Jim Weldon 10 

None submitted. 

10 James H. Weldon, PE, Dam Safety Engineer, Denver Water Board, 1600 W. 12th Ave., Denver, CO 
80204, phone: 303-628-6657, james.weldon@denverwater.org 

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General discussion  Consultants Spillway Design and Research Needs 

Wade Moore 11 

None submitted. 

11 Wade Moore, Senior Hydraulic Engineer, Montgomery Watson Harza (MWH), 175 W. Jackson Blvd., 
Chicago, IL 60604, phone: 312-831-3098, wade.p.moore@mwhglogbal.com 

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Vegetated Earth Spillways - Inspection, Maintenance and Monitoring 

Morris Lobrecht 12 

NRCS experience with earthen spillways suggests that they generally perform well for 
infrequent flows. However, problems have been encountered when spillways are not 
properly designed or maintained. Performance examples from NRCS experience range 
from good to bad. Properly designed and maintained spillways with good vegetal cover 
have withstood large flows with minimal damage. Other spillways that were properly 
designed, but lacked uniform vegetal cover protection, have suffered damage with 
relatively low flows. In many cases maintenance was a problem. Maintenance, 
vegetation, and soil characteristics determine the performance of earthen spillways for a 
given flow event. 

12 Morris Lobrecht, Design Engineer, United States Department of Agriculture, Natural Resources 
Conservation Service NRCS, P.O. Box 6567 Fort Worth, TX 76115, phone: 817-509-3775, 
morris.lobrecht@ftw.arcs.usda.gov 

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Earth Spillways- State of Practice and Research Needs 

Greg Hammer 13 

Introduction 

The choice to use an earth channel spillway is typically driven by the economics of 
design, and its simple construction. However, as the low cost is a product of the ease of 
excavation and material placement, these same properties are the basis for the limited 
resistance to hydraulic loading, as is evidenced by eroded channels after flows occur. The 
initial process of design of the spillway may dictate the dimensions to safely route the 
inflow design flood (IDF), but the final design phases are driven by how to prevent, or at 
least limit the erosion that will inevitably occur after operation of the channel. The 
dilemma for the engineer regarding the design of an earth channel thus becomes not only 
how large the spillway must be to pass a given design flow, but also how to keep the 
channel intact during flow, and how to be sure that spillway will be clear and available 
when the occasion for flow presents itself. 

State of Practice 

In current practice it has been my observation that earth channels are immensely popular 
because construction requires no high-tech tools, or high-cost products. Concrete 
structures require forming, and quality control to assure that the final product is as 
designed. Earth channels however are created with little more that excavation by any 
simple means, followed by final grading to dress-up the appearance of the channel. Based 
upon evaluation of the material within which the channel was excavated, some remedial 
measures may be necessary to lessen the erosion attack, either by the use of rip-rap or a 
sill wall. 

A typical design for an earthen spillway will include the process of sizing to route the 
IDF, then consider what armoring requirement will be necessary. The NRCS procedures 
based upon the bulk length are commonly used to evaluate erosion attack, and identify 
velocities that may be excessive. It may be necessary also to use a concrete sill wall to 
provide a measure of protection against the anticipated head-cutting. No clear guidance 
has been identified however as to where and when a sill wall may be required, or to 
provide a proper design. 

Research Needs 

Spillway capacities: Typically the capacity of a spillway will be calculated based upon 
either the broad-crested weirs formula, or uniform flow conditions using Mannings 
equations. Backwater analysis techniques (HEC-RAS, HEC-2) are often utilized, but can 
give results that differ markedly from the more popular formulas. Recent evaluation 
studies of spillways in Colorado have been found to give varied and unexpected results 
for channel spillways. Typical references (Brater & Street) depict values in the range of 

13 Gregory Hammer, Dam Safety Engineer, Colorado Division of Water Resources, State Dam Safety 
Office, 810 9th St., #200, Greeley, CO 80631, phone: 970-352-8717, greg.hammer@state.co.us 

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2.5 2.7 for a typical earth channel spillway configuration, however HEC-RAS analyses 
have yielded values as low as 1.5. Conversely, there have been some instances where the 
flow coefficient has been found to be much higher than is reasonably expected. 

Once the design flow has been identified, the channel must be evaluated for erosion. This 
requires an assessment of velocities and soil properties of the channel. NRCS has 
conducted much research in this arena based upon generalized soil conditions. On a 
micro scale, erosion occurs due to irregularities in soil properties or the channel. A 
common protective measure is a sill wall to retard the advance of head-cutting of the 
channel. Development of design techniques for sill walls would enhance our confidence 
in the ability of the channel to defend against erosion. This should include how frequently 
to space sill walls, and how deep to construct them when they cannot be placed on 
bedrock. 

For the spillway to function as designed, another consideration is the aspect of keeping 
the channel open and unobstructed. Floating debris is a typical concern, but proper 
attention to maintenance can resolve that concern. In Colorado, we face the problem of 
snow and ice settling into the spillways. We have become aware of some research in 
Scandinavian countries, but little information has as yet been disseminated to engineer 
community. This concern is typically recognized at existing structures, and in many cases 
requires owners to venture to the dam before the snowmelt period begins to excavate the 
blockages and clear the spillway. On a case-by-case basis, some work has begun to 
design service spillways that can limit reservoir levels until natural melting will clear the 
emergency channel. Another method is to provide for a cover to create a low flow 
channel that can pass flows to encourage melting. 

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Issues and Research Needs Related to Hydraulics for State Regulated Dams 

Ed Fiegle 14 

There are over 75,000 dams listed in the National Inventory of Dams. Ninety percent of 
these dams are regulated by state dam safety programs. They range in size from very 
small run of river dams all over the country to very large storage and flood control 
projects in the West. A survey was prepared and sent out to all ASDSO state 
representatives to prepare information on design and research needs for the workshop. 
The following questions were asked: 

* Types of spillways? 

* PVC siphon spillways? 

* Ice and snow effects on hydraulics? 

* Skimming flows on stepped spillways? 

* Questions about hydraulics of spillways? 

* Adequate training? 

* What are the hydraulic issues with spillways that need further research? 

Responses were received from 30 states. The responses will be summarized and 
presented at the workshop. The primary research needs as compiled from the state 
responses were in the following categories: 

* Snow and ice issues (16 states) 

* Stepped spillway design and longevity issues (7 states) 

* Siphon design and integrity issues (6 states) 

* Concrete block system issue (5 states) 

* Hydraulic designs relating to spillway coefficients (5 states) 

* Irregular spillway shapes (4 states) 

* Drop structures (3 states) 

The most important factor in performing research was that it must be relevant and reliable 
and the results needed to be proven in the field in long-term applications. 

14 Francis (Ed) E. Fiegle II, PE, Program Manager, Georgia Safe Dams Program, Environmental Protection 
Division, Georgia Department of Natural Resources, 4244 International Parkway Suite 110, Atlanta, GA 
30354, phone: 404.362.2678, ed_fiegle@dnr.state.ga.us 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

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Concrete Spillway Repairs 

Jim McDonald 15 

The unacceptably high failure rate for concrete repairs is a major problem in repair of 
water-resource infrastructure and the overall concrete repair industry. It is generally 
acknowledged that the primary problem is cracking of repair materials - typically the 
result of dimensional incompatibility between the repair material and the concrete 
substrate. To achieve durable repairs, it is necessary to consider the factors affecting the 
design and selection of repair systems as parts of a composite system. Compatibility 
between repair material and existing substrate is one of the most critical components in 
the repair system. Unfortunately, information on material properties that affect 
dimensional compatibility, how the various properties interrelate, and values that should 
be specified as performance criteria for individual properties is very limited. 

To address this need, the Corps of Engineers initiated a two-phase program of research in 
1994 to develop performance criteria for dimensionally compatible cement-based repair 
materials that will provide durable crack-free repairs. Results of laboratory and field 
performance tests were correlated to provide a basis for development of performance 
criteria for the selection and specification of dimensionally compatible cement-based 
repair materials. Performance criteria include a minimum value for tensile strength and 
maximum values for modulus of elasticity, drying shrinkage, and coefficient of thermal 
expansion. Also, resistance to cracking in restrained shrinkage tests is a requirement. A 
data sheet protocol was developed for cement-based repair materials that will provide 
reliable, standardized information on pertinent material characteristics. Results of the 
overall investigation are summarized in Technical Report REMR-CS-62. Also, a 
summary paper is available on the High-Performance Materials & Systems (HPM&S) 
Website (http://www.wes.army.mil/SL/HPMS/bulletins.htm). 

15 James E. (Jim) McDonald, MS, PE, consultant, 1414 Huntcliff Way, Clinton, Mississippi 39056, Phone: 
601-924-5955, Fax: 601-924-1115, jmcdonald10@jam.rr.com 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-22 

Inspection of Concrete Spillways  Gated and Uncontrolled 

Bill Bouley, P.E.16 

The inspection of spillways requires qualified technical staff able to recognize 
satisfactory performance and to identify developing problems. The inspection techniques 
are similar for gated and uncontrolled spillways and can be also be applied for outlet 
works inspections. Earth-lined spillways are evaluated similar to embankment dams, but 
with special consideration given to approach (inlet) and discharge areas. 

For the various spillway gates, an exercise or testing program should be established. A 
partial opening cycle of less than a ten percent opening should be used at least annually to 
ensure the hoist equipment and gates can operate in a satisfactory manner. Full cycle 
operation is desired to verify that there are no obstacles to releasing floods from the dam. 
These tests are conducted less frequently than the ten percent opening cycle due to the 
concerns about releasing large amounts of valuable water supply and impacting 
downstream residents. These full cycle tests are generally conducted at the end of an 
irrigation season or other periods of low reservoir elevations. Debris booms are needed 
where the potential for flow obstruction exists. Innovations to the original gate design 
that improves performance and reduces maintenance should be identified. 

Uncontrolled spillway crests should be examined during discharge conditions and when 
not in use to determine if any deficiencies are present. Latent construction defects can 
appear during high reservoir conditions such as leakage through lift lines. Glory hole 
spillways should be isolated from public access by buoys or booms from the reservoir. 
The ideal inspection opportunity for these spillways is during reservoir conditions when 
the water surface approaches the spillway crest. This allows the examiner to identify 
possible shifting of the crest structure foundation. 

Chutes, tunnels, stilling basins are the most critical features of the spillway, as they must 
pass discharges safely past the dam without eroding the abutments or foundation. 
Deflections and offsets in the walls and chute floor should be noted as they pose an 
impediment to flows and could lead to future damages. Patterns of flow should be 
observed either at the time of discharge or by observing water stains on the chute to 
ensure flow patterns are acceptable. Trees and brush should be removed and kept clear of 
the structure for a distance where such growth will not impact the structure or impede 
flows, usually a minimum clearance zone of 15 feet. In tunnel sections, offsets have led 
to cavitation damage at Glen Canyon Dam that required air slot installation. Drains 
constructed to prevent back pressure from groundwater should be cleared on a periodic 
basis. 

Stilling basins are vulnerable to damage from excess surcharge to the walls or 
freeze/thaw cycles that can weaken the concrete. With basins that are constantly 

16 Bill Bouley, P.E., Civil Engineer, US Bureau of Reclamation, Technical Service Center, Inspections and 
Emergency Management Group, Denver, Colorado, P.O. Box 25007, D-8470, Denver, CO 80225, phone: 
303-445-2754, bbouley@do.usbr.gov 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-23 

underwater, hidden defects can go unrecognized until they become more serious as can 
be the case with ball milling action when rocks become drawn into the basin. 

Inspection techniques employed vary from the visual above ground evaluations for the 
majority of the spillway structure that are conducted with the overall facility 
examinations (conducted by local staff monthly, area staff annually, and regional staff 
and Technical Service Center staff alternating on a three year basis) to the more 
specialized examinations that are performed less frequently. Climbing and underwater 
inspection services are needed for areas that are difficult to access. These specialized 
services should be aware of any inherent hazards associated with examining water 
storage features. Whether for climbing or underwater services, in manned teams, there is 
a requirement for at least three team members, two conducting the actual structural 
examination, and a third member to be in communication with the team and to be in 
reserve should problems arise. Climbers are limited to their endurance and equipment 
constraints. Divers have limitations imposed by altitude and depth, restricting their 
duration underwater. Remote-operated vehicles are useful in visually monitoring 
underwater conditions, but physical conditions of structures cannot be adequately 
determined without the ability to check concrete and metalwork soundness. 

Monitoring has consisted of survey measurement point installed along the spillway walls 
and chute floor. Surveys of smaller structures that show little movement over a 30-year 
period may be curtailed until a significant event (flood or earthquake) occurs in the area. 
Crack monitoring and mapping is used where needed. Other instrumentation is installed 
depending on site conditions and failure mode concerns. 

Concrete repair methods and materials are being analyzed constantly by Reclamations 
laboratory personnel to better assist the field staff. Non-destructive evaluation techniques 
are used to identify the extent of problem areas. In-place concrete strength tests, 
ultrasonic, x-ray, infrared, and several other processes are used to conduct nondestructive 
evaluations. Unfortunately, to obtain the services of these specialists, field 
personnel need to provide the funding for such advice, as there is not an agency 
infrastructure fund. 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-24 

Geophysics for Spillway and Seepage Evaluation 

Mark H. Dunscomb, P.G.17 

Geophysics arguably has a greater ability to lower subsurface risk on a project for every 
dollar spent than any other investigative technique. It can not and should not totally 
replace intrusive methods but, in combination with these methods, it can used to reduce 
the number and cost of intrusive probes by helping to locate them more effectively, use 
probes to calibrate geophysical findings, and vastly improve overall subsurface 
understanding. Geophysics is non-invasive and non-destructive. It can help characterize 
the subsurface over broad areas and depths both quickly and cost effectively. It can 
screen an area for specific objects (e.g. voids, pipes) and provide in-situ estimations of 
some key physical properties. Specifically, with regard to dams, we have used 
geophysics to trace seepage through a variety of embankment and gravity dam 
configurations; test concrete arches for weathering and deterioration of concrete; locate 
abandoned diversion pipes; and look inside of and underneath concrete spillway slabs 
to map voids, trace seepage and locate steel reinforcing. 

Research Needs 

While geophysical techniques and applications continue to develop, there appears to be 
little need for basic research into the principles and applications of geophysical 
applications for dams and spillways. What does appear to be needed is the development 
of a State of the Practice document for application to dams. There are numerous tools 
available for geophysical exploration and each has its strengths and weaknesses. In 
addition, significant advantages can many times be gained through the overlapping 
application of two or more techniques. Development of a document that provides a clear 
and concise overview of geophysical applications for evaluating dams would have broad 
application and would bring significant value to the dam safety community. 

17 Mark H. Dunscomb, P.G., Associate, Schnabel Engineering, Inc., 510 E. Gay St. 
West Chester, PA 19380, phone: 610-696-6066, Mdunscomb@schnabel-eng.com 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-25 

Inspection, Maintenance and Monitoring of Service and Emergency Spillways 
Dan Johnson 18 

Introduction 

There is an old dam Owners mentality that is slowly changing from one that the dam did 
not need observation and upgrading to one where more attention is taken to ensure long, 
safe operation. This change involves more attention to maintaining the ability of a dams 
components to perform as designed. At the same time, however, the costs of upgrading 
projects are more than Owners can afford. Modern technology has created less expensive 
upgrades for spillways that may have less redundancy than those prior in-the-abutment concrete-
spillways. 

As always, the general public has short memories and does not believe that significant 
events do occur. Who remembers the 1913 snowstorm in Denver that dumped 7 feet of 
snow? Very few, and so Denverites were ill prepared for the 2003 March snowstorm 
which dumped 4 feet. There is a general lack of good prototype experience; because 
design events occur so rarely that we do not get to evaluate the real conditions and 
behavior. We attempt to model with scale physical and digital models, but they may fall 
short in evaluating the behavior of water flow on designed earth and concrete spillway 
structures during the real event. We need to be observing the real events as they occur 
and the ability of spillways to perform as designed. 

Inspection 

Prior to an inspection an understanding of the failure modes for the particular spillway 
system is needed. Also, an awareness is needed that the service spillway may see use on 
a regular basis, where as, the emergency spillway may have never been used. Therefore, 
the condition of the spillways, based on wear may be quite different. Both types of 
spillways do erode, deform and age. The inspector must be trained in the issues for the 
particular type of spillway, its use and the aging impact on the materials used in 
construction. 

It is valuable to observe spillways in operation during normal and greater than normal 
operations to provide a better understanding of the flow and erosion that occurs on a 
regular basis. The infrequent large flood may not be the worst impact on the longevity of 
a spillway, but the annual, 5 and 10-year floods may. Observation of the spillway during 
the 25-year flood may give indication of the potential for the spillway to survive the 
design flood. 

Maintenance 

Maintenance of most dams (small to medium sized) may be on an infrequent basis and at 
the behest of the safety agency, not the Owners wishes. On the occasions of 
maintenance, the service spillway generally gets greater recognition, as it should, because 
it sees more use and has wear issues to correct. However, emergency spillways need to 
be in good repair for performing correctly when called into use. Concrete structures are 

18 Mr. Daniel Johnson, PE. MS., Vice President and Director of Domestic Hydropower and Dams, 
Montgomery Watson Harza (MWH), Americas, 370 Interlocken Blvd., Broomfield, CO 80021, phone: 
303-410-4189, daniel.johnson@mwhglobal.com 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-26 

subject to movement and cracking, erosion of foundation materials, deterioration, and 
collection of deleterious materials. Earth spillways are subject to deterioration of the 
slope protection materials (riprap, vegetation, etc), erosion from flows and slope 
movements. Over-the-top spillways, as being used on many embankment dams today, 
are subject to movement, cracking and aging of materials and require special 
considerations due to the high consequence of their failure. 

Monitoring 

Monitoring and evaluation of monitoring data is the best way to predict potential 
performance in all types of spillway events and to set a plan for maintenance and 
upgrading of spillways. The measurements to be taken on a particular spillway system 
are very specific to the dam, its features, and its operation. Each facility is different. 
Typically measurements of movement, cracking, deterioration and aging issues are 
typical of service and emergency spillway monitoring plans. 

Data from monitoring is of little value unless it is used. Many dam owners have stacks of 
data that have never been reviewed. Documents such as survey records, photos, 
checklists and inspectors notes need to be viewed by knowledgeable personnel when 
first gathered and then compared to subsequent years documents for evaluating 
performance and changes from historic to current. 

Closing 

Despite our toughest desires, aging is occurring and with it several things become 
obvious. The initial design may not have been to the level of safety now required for the 
spillway(s) and the changes that are occurring are detrimental to successful operation of 
the spillway(s) 

As we have all been taught, dam failures occur and spillways are the leading cause, and 
inspection, maintenance and monitoring are tools we use to ensure that the spillway will 
safely function when needed. 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

B-27 

Unlined Spillway Erosion Risk Assessment 

Joe Koester 19 

Spillway erosion analyses are affected by the highly variable nature of spillway 
geometry, geologic material, and unpredictable flood events. Improved tools are 
urgently needed to determine probability of spillway damage as part of portfolio risk 
assessments of dam safety, in order to effectively prioritize remediation activities. 
Essentially, the purpose of risk assessment in these cases address three main questions: 

* What can go wrong? 

* What is the likelihood it can go wrong? 

* What are the consequences? 

Nested uncertainties compound the problem; this research investigates the relative 
effects of uncertainties associated with flood events, material properties, and performance 
of unlined spillways. Various logistic regression techniques are presented and applied to 
quantify erosion potential against known site performance data. 

19 Joseph Kester, Supervisory Research Engineer, CEERD-GS-E 3909, Halls Ferry Road, Vicksburg, MS 
39180-6199, phone: 601-634-2202, Joseph.P.Koester@erdc.usace.army.mil 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

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Appendix C 

Presentations 

This appendix provides the MS Word PowerPoint presentations of the state-of-practice 
regarding dam service and/or emergency spillways. All the presentations presented at the 
workshop are included in this appendix as documentation of the state-of-practice and 
research needs as seen by the presenting experts. 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 1

Presentation 1: 
Hydraulic Design of Labyrinth Weirs 
and Fuse Gates 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 3 

Hydraulic Design Of 
Labyrinth Weirs 

Henry T. Falvey & Associates, Inc. 

0utline of Presentation 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Types of Weirs

Side Channel
Skew
Folded, Accordion, or Corrugated
Duckbill or Bathtub
Labyrinth

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Nappe Interference 

Streamline
3-D View
Weir Crest
Disturbed Area
PLAN 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Effective Disturbance Length 
(1-Cm)Ld = Lde 
Effective 
Disturbance Length

Interference Effects

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Design Curves  Lux/Hinchliff

Henry T. Falvey & Associates, Inc. 

Design Curve - Tullis 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Nappe Oscillation - Milton Reservoir 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Solutions to Nappe Oscillation 

FLOW - FLOW - 
Radius Angle Iron 
FLOW - FLOW - 
Splitter Roughness

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Geometric Definitions 

Design Considerations - New versus Old 

* Lux recommends 0.45 < Ho/P < 0.55 
W/P = 2.5, and 2 < L/W < 6. 

* New criteria allows Ho/P to be as high 
as 0.90, W/P is superceded by 
interference ratio (Lde/L) and L/W 
superceded by efficacy. 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Design Considerations - Efficacy 

Efficacy 

Sidewall Angle, degrees

Henry T. Falvey & Associates, Inc. 

Design Considerations - Position 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Research Needs 
* Crest Shape 
* Interference Verification 
* Need for Splitters on Crest 
* Approach Flow Considerations 
* Raised Invert Effects 

Henry T. Falvey & Associates, Inc. 

FUSEGATES 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Fusegate Geometry

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Profile

Tilting Range Ballast 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Elevation 

Ballast Crest Length = 5.22 H 

Henry T. Falvey & Associates, Inc. 

Forces on Fusegate 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Moments on Fusegates 

Tipping Range
Flow Begins to Overtop Gate
Restoring Moment
Overturning Moment
Water Surface Height ( H - h ) / H 

Henry T. Falvey & Associates, Inc. 

Fusegate Chamber Pressures 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Discharge Characteristics 

Rehbock Equation

Henry T. Falvey & Associates, Inc. 

Issues with Fusegates 

* Wave loading has been studied 
* Ice loading has been studied 
* Seismic loading has been studied 
* Tailwater effect has been studied 
* Downstream channel clogging has been 
studied 
* No major research needs 

Henry T. Falvey & Associates, Inc. 

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Presentation 2: 
Fuse Plug Embankments -State of the 
Art and Practice, and Research Needs 

16 FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Fuse Plug Embankments
State of the Art and Practice, and Research Needs

Tony Wahl
Bureau of Reclamation
Water Resources Research Laboratory

* Design concept by Tinney and Hsu (1961)
- Proven in their lab tests, Oxbow field test, and 1980s Reclamation lab tests 
* Core is inclined downstream
- Failure is by scouring out non-cohesive supporting zone, causing core to be a cantilevered beam
- Initiation is reliable, rapid
- Lateral erosion rate is predictable, depends on head and embankment cross section 

16 FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Design Concept

Laboratory Testing

State of the Practice
* How many have been built (or are being built)?
* What design concept are they using?
- Tinney & Hsu inclined core
- More traditional embankments
- Vertical core or homogeneous fill
* Operational history

State of the Practice
* Reclamation fuse plugs
- Horseshoe and Bartlett Dams
- 262,000 cfs (~10 yrs)
- New Waddell Dam
- 5,500 cfs (~10 yrs)
- Sumner Dam
- 150,000 cfs (1955)

16 FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Fuse Plug at New Waddell

State of the Practice

* Fuse Plugs Built by Others
- Center Hill Dam (USACE) (USBR consulted)
- Lake Pontchartrain fuse plug levee (1936)
- Yahekuo Dam, China (vertical, tapered core)
- Fuse plugs reported to be widely used in China
- Arvada Reservoir (10- bay homogeneous 
embankment) considering rehab 
- Manny, many small dams
- e.g., 4 dams North Carolina (Nantahala Power)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Operating History

* Very few spillways have operated
- Oxbow Field Test was a prototype
- Fuse plug at Silver Lake on Dead River in Upper Peninsula of Michigan failed (?) in May 2003.
- Greater portion than anticipated gave way
- Apparently eroded too deep no fixed sill
- Nobody I talked to was willing to say much right now

Research Needs
* Investigating long-term stability of inclined clay core
- Cracking due to dessication bi differential settlement
- issues of concern on SRP fuse plugs
- Contact with floor and side walls 
- Is long-term water storage against a fuse
plug desirable, undesirable, or not an issue?

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Research Needs

* Designs utilizing other materials that 
might offer better long-term 
performance or ease of construction 
- Impermeable membranes 
- Inclined concrete core
* Research to define inventory of fuse
Plug spillways, their design concepts,
And operational histories

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Presentation 3: 
Crest Parapets and Dam Raising 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Crest Parapets/Dam Raising 

Dwayne Fuller
U.S. Army Corps of Engineers
Engineer Research and Development
Coastal and Hydraulics Laboratory

Recent Projects

* Tygart Dam, Tygart River, West Virginia, Pittsburgh District
* Original Design Flow, 270,000 cfs
* PMF Flow, 373,000 cfs
* 38% increase
* Bluestone Lake Dam, New River, West Virginia, Huntington District
* Original Design Flow, 430,000 cfs
* PMF Flow, 950,00 cfs
* 120% increase

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 
Typical Model Objectives

* Extend rating curve
* Crest pressures
* Gate and pier pressures
* Energy dissipation component forces
* Stilling basin forces
* Scour pad forces 
* Tailrace sour 

Tygart Dam

Alternatives
* No action 
* Raising the dam (approximately 6)
* Spillway medication (gated spillway with lower crest)
* Auxiliary spillway 
* Overtopping 
* Dam replacement 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Tygart Dam

1:60 Scale Model

Tygart Dam

Flows With Existing Structure

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Tygart Dam

Redirected Spill

Tygart Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Bluestone Lake Dam

1:65 Scale Model

Bluestone Lake Dam

Alternatives 
* No action 
* Raising the dam (approximately 14) 
* Spillway modification 
* Auxiliary spillway 
* Overtopping (partial) 
* Dam replacement

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Bluestone Lake Dam

Original Design Flow

High Flow

Concerns

* Spill capacity (PMF passage)
* Stilling basin 
* Cavitation (spillway and penstocks)
* Erosion 
* Component inadequacy 
* Hydraulic loads 
- Forces on side walls
- Basin forces
- Forces on temporary structures 
* Flow conditions in tailrace 
* Debris build-up in basin (side flow) 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 

Possible Research Needs
* Effects of side flow into stilling basin
* Debris damage in basin
* Force measurement techniques
* Temporary structure design criteria

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Presentation 4:
Gated Spillways: Enlargement, Modification,
and Rehabilitation -State of the Practice

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

GATED SPILLWAYS
Enlargement, Modification
And Rehabilitation
State of the Practice

GATED SPILLWAYS
* Determine Function and Needs
* Risk Neutral
* Types 
* Design & Research Needs

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

DETERMINE FUNCTION AND NEEDS
* High Head vs. Low Head
* River Flows 
* Storage Issues of Large Floods (>100 Yr)
* Maintenance
* Attendance issues

DESIGN AND DATA NEEDS
* River Flows
- Normal
- Annual river flows
- Minimum Flows
- Is a bypass needed?
- Maximum Flows
* Storm Storage

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

DESIGN AND DATA NEEDS (cont)
* Climatic Conditions
- Temperature changes
- Winter Conditions
* Reservoir fluctuations
* Vandalism
* Security Issues
* Debris
DESIGN AND DATA NEEDS (cont)
* Controls & Automation - operate - remotely or onsite
* Emergency power
* Flow measuring capability 

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

TYPES
* Slide Gates
* Wheel Gates
* Radial Gates
* Drum Gates
* Crest Gate
* Rubber Dams
* Fusegates
* Flashboards

Slide Gates
(Unbonneted)

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Wheel Gates

Radial Gates

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Top Seal Radial Gates

Drum Gate

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Crest Gate
(Obermeyer Gate)

Rubber Dams

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Fusegates (Hydroplus)

Other Types of Gates
* Flashboards
* Cylinder Gates
* Other

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

RESEARCH NEEDS
* Discharge data
* Submergence effects on discharge
* Extrapolation to other situations
* Flows released during failure
* Seismic and security modifications
* Cost
* Maintenance and Durability

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Presentation 5:
Earthen Spillways Design and Analysis
State of the Practice

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

USDA United Stated Department of Agriculture

Agricultural Research Service

Thank you. I am with the Agricultural Research Service, and one of the first
questions that may come to mind is "What interest does the Agricultural Research
Service have in Spillways?"

As the research arm of the USDA, we are responsible for performing the research
needed by action agencies; including the Natural Resources Conservation Service.
Within USDA, only the Forest Service has its own research branch. Therefore,
although we do cooperate with Universities and other Federal agencies, and I'll try
to touch on some of their concerns, my discussion today will generally be from the
perspective of the USDA.

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

I EARTHEN SPILLWAYS

Prepared for the
Issues, Remedies, and Research Needs Related to Dam Spillways Workshop

USDA has significant experience with vegetated earth spillways, and has collected
substantial field data from spillway flow events.

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency Spillways

Enlargement, Modification, Retrofitting of Dam Service
And/or Emergency Earthen Spillways
Considerations

* Large number of existing earth spillways.
* Designed under varying criteria
* May have inadequate capacity
* May have inadequate maintenance

The Earth Spillway must pass the design storm without breach

The primary concern that is unique to earth spillways is that they are erodible. Or at
least we hope that we don't have that problem with other spillways. In general, the
philosophy has been that, because flows are infrequent, some erosion may be
acceptable providing the spillway is able to pass the design storm without failure.
Because they often offer economic and aesthetic advantages, there have been a large
number of earth emergency or auxiliary spillways used. USDA has assisted with
the construction of over 10000 flood control reservoirs, and most of these have earth
spillways. They have also been used on other dams either alone or in combination
with structural components.
They have been designed using various criteria. And I'll touch on that more in just a
moment.
As with other types of spillways, the capacity may be inadequate. This may be due
to a number of factors, but for USDA assisted dams, the most common reason is a
change in hazard classification changing the design storm.
Inadequate maintenance can also create problems. Vegetation and earth are often
thought of as not requiring maintenance, but in some instances, maintenance may be
%i~m6&tl,fs~~~, Remedies aM Rerarch Needs Relating a servic. anarer Emergency Spillways
EARTH SPILLWAY DESIGNlANALYSIS
Historic Approaches
No Design
Stable Exit Channel
Permissible Velocity
Allowable Stress
Sediment Transport
Bulk Length
Looking at the approaches used to design earth spillways during the glory years of
dam construction, the first approach was to just let it happen. This approach was
generally only associated with smaller agricultural dams in the early years when
some engineers tended to be of the opinion that the emergency spillway would
never flow anyway and the spillway was just a convenient borrow for the dam
construction.
On the other end of the scale was design of the spillway to conduct the design flow
as a stable channel. The tools applied were generally the clear water approaches of
permissible velocity or allowable stress, but more sophisticated procedures were
sometimes used. These procedures were more often applied to larger spillways
with longer flow durations. Designing channels using procedures developed for
application to canals or stream and river channels tended to be somewhat
conservative because of the infrequent and limited duration of spillway flows.
In the 70's the Soil Conservation Service moved to an approach that included both a
stable exit channel component and a bulk length, or volume of erosion approach.
The exit channel was designed to be stable for an emergency spillway design storm,
usually defining the width of the spillway. The concept here was one of the channel
not requiring maintenance for less than the emergency spillway storm.
The spillway was also required to have a bulk length determined by the geologic
material and the total discharge per unit width of spillway for the freeboard storm.
The bulk length was defined as the distance through the crest 2 feet below the
rk&b I ues, Remedies and Research ~ e e d s Relating to Service andlor Emergency spillways 45 hb#ku!c c o k 8 .
Current Tools
Stable Exit Channel
It may still be appropriate to use channel design and analysis software for spillway
design or evaluation. This is particularly true when long exit channels are involved
and sediment transport is expected to be a major consideration.
48 FEMA Workshop - Issues, Remedies ancl Research ~eeds Relating to service and(or Emergency sprlhvays
EARTH SPILLWAY DESIGNlANALYSIS
*tt arttee mat
Current Tools
Stable Exit Channel
REMR Erosion Prediction Method
Other tools have also been developed, including the REMR erosion prediction
method developed by the Corps.
FEMA Wbrksnop - ~ssues, Remedies and Research ~ e e d s Relating to Service andlor Emergency spillways 47
ERMION
RISK
EROSION RISK CLA88
This empirical method is based on a combination of experience and judgment that
compares an erosion risk class that includes hydraulic attack in the form of
maximum mean velocity, against
48 FEMA Workshop - Issues, Remedies ancl Research ~eeds Relating to service and(or Emergency sprlhvays
Erosion potential classes. Note that here, the table has been truncated, there is more
geologic information required than shown; and that the focus tends to be on rock
materials. If the erosion risk is greater than the potential, then damage is expected.
FEMA Wrksnop - ~ssues, Remedies and Research ~ e e d s Relating to Service andlor Emergency spillways 48
EARTH SPILLWAY DESIGNlANALYSIS
.state art t8e PFPcth
Current Tools
S W Wud
*lmMRMalr warn ~ d i a d '
Sites Spillway Erosion Analysis
The approach that is presently used by USDA's NRCS far design and analysis of
earth spillways is that incorporated into the Sites software. I'll take a few minutes
to go into the basis for this procedure, and then address some of its limitations as we
move into the research needs.
50 FEMA Workshop - Issues, Remedies ancl Research ~eeds Relating to service and(or Emergency sprlhvays
I VEGETATED AUXILIARY SPILLWAY
The Sites software uses a three phase spillway erosion model to evaluate the potential for spillway
breach. The beginning point for the conceptual model is a spillway such as we see in the
background. For this condition, the erodible boundsty is initially protected from erosion by the
presence of the grass cover. However, if the flow persists long enough or the stress is high enough,
erosion will be initiated in a weak area (Natural materials such as vegetation and soil are never
homogenious), and the covet will begin to unravel. The weak area will enlarge until the vegetal
cover is no longer effective and the flow tends to concentrate in the local emding area That local
removal is phase 1 of the failure process.
FEMA Workshop - ~ssues, Remedies and Research Needs Relating to service andlor Emergency spillways 51
VEGETATED AUXILIARY SPILLWAY
Phase 2 of the process consists of enlargement and deeping of the emdug a m due surface
detachment as a result of the flow arad stress concentrations. The end of this phase is the point where
the flow tends to break up, and a headcut is formed. The depth of erosion corresponding to the end
of phase 2 is discharge dependent.
52 FEMA Workshop - Issues, Remedies ancl Research Needs Relating to service and/or Emergency spillways
VEGETATED AUXILIARY SPILLWAY
The third phase of the failure process is the deepening and upstream movement of
the headcut. Widening occurs simultaneously, but is not tracked by the present
Sites computations.
For worst case conditions, the upstream advance of the headcut may result in
spillway breach and drainage of the reservoir. However, the Sites model was
developed only to evaluate potential for breach, and does not take the computations
on through the actual breach process. We're working on that for embankments and
consider the development of that phase of the model to be a research need.
FEMA Workshop - ~ssues, Remedies and Research Needs Relating to service andlor Emergency spillways 53
Another thing that is introduced in the sites model is the concept of major and minor
discontinuities in the vegetal cover. These can be very important for spillways
designed for low head conditions in highly erodible materials. Minor
discontinuities are those such as cross-roads, or trees;
Major discontinuities such as access roads immediately concentrate the flow and
essentially negate phase 1 protection.
Note also, that for large heads and steep exit channel slopes, phase 1 protection may
not be significant anyway.
54 FEMA Workshop - Issues, Remedies awl Research Needs Relating to Service and(or Emergency spillways

Summary

Three-Phase Erosion Process

1. Surface Erosion (Cover Protection)
- Surface Discontinuities
- Sod Stripping

2. Concentrated Flow Erosion

3. Headcut Advance and Deepening

Briefly then, the Sites model describes a three-phase process of surface cover
failure, including accounting for discontinuities. We also account for stripping of
shallow rooted covers, although I didn't cover that for reasons of time today.
The second phase is a concentrated flow erosion leading to the development of a
headcut,
And the third phase is the deepening and upstream advance of that headcut. Each of
these phases is described in the model by it's own set of threshold-rate relations.
The relations tend to be a somewhat simplified representation of the processes, and
I'm going to go through them rather quickly as a lead-in to the weaknesses and
research needs.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 55

Phase 1: Vegetation

Effective Stress

Te=yds(1-Cf)(ns/n)2

Phase 1 uses an erosionally effective stress approach that computes gross stress
from normal depth, gamma d S, and adjusts it for the type of cover I -Cf, and for the
transfer of stress to the boundary by the plant root system ns/n squared.

56 FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Phase 1: Vegetation

Surface Detachment

Er = kd(te-tc)a
Er = the rate of detachment
Kd = coefficient of detachment
te = effective stress
tc = critical tractive stress (~0)
a = exponent (~1)

This is combined with an excess shear detachment rate relation with the critical
shear stress assumed to be negligible. The assumptions that the process is
detachment limited and the material is fine gained tend to be reasonable because
we are applying the relations to spillway flow over vegetation. When the material
does not support vegetation, phase 1 tends to be negligible, and we immediately
move to phase 2.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Data that is used in the model for Phase 1

1000 800 600 400 200 0
0 6 10 15 20 25 30
Damaged
Slight Damage
Undamaged
Ftedt, Pa-h
Ef/k6 = 9(Iw) + 50

PLASTICITY INDEX, Iw

The failure point is calibrated to field data, and tends to tit the available data fairly well. Note
that the material properties are represented by plasticity index for this phase.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 2: BARE EARTH
Concentrated Flow
Effective Stress

Te = y(d+Ad)s

Since phase 2 is also surface detachment, we also use the same stress approach, but now.
we assume that all of the stress is effective in detaching material, and account for flow
concentration by assuming the water surface elevation in the eroding area is controlled by
the surrounding flow.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 2: BARE EARTH
Concentrated Flow
Surface Detachment

Er = kd(te-tc)a
Er = the rate of detachment
Kd = coefficient of detachment
te = effective stress
tc = critical tractive stress (~0)
a = exponent (~1)

We also use the same detachment rate relation, but now, the critical stress is a
function of particle diameter based on Shields diagram, and Kd is determined
explicitly.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 2: BARE EARTH
Concentrated Flow
DETACHMENT RATE

kd = 5.66yw/yd exp[-0.121(c%)0.41(yd/yw)3.10]

kd = detachment rate coefficient
c% = percent clay
yd = dry unit weight
yw = unit weight of water

Kd may be measured for soil materials using the jet test for erodibility or estimated from
percent clay and density. This means that for soil materials, phase 2 tends to be dominated
by the clay and density properties, whereas for rock, particle diameter dominates. We are
still assuming detachment limited conditions and concerning ourselves with a point in the
spillway.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT
Downcutting Component
EFFECTIVE STRESS

Te = ydc 0.011(H/dc)0.582 
dc H te

Phase 3 is divided into two parts for computation. The downward movement and
the headward movement. For the downward component, surface detachment is
taking place, and we continue to use an excess stress approach with the stress
computed assuming low tailwater conditions. The detachment rate relation is the
same as applied previously.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT
Advance Component

dx/dt = C(A-Ao)

dx/dt = rate of headcut
migration,
C = material dependent
advance rate coefficient,
A = hydraulic attack (Power dissipated), and
Ao = material dependent threshold.
The headcut advance relation is of the same general threshold rate form as the other
relations, but is energy rather than stress based. Although several modes of headcut
advance Rave been observed from undercutting to surface detachment on a steepsloped
face, all have in common the focused dissipation of flow energy.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT
Advance Component

As applied, both the threshold and the rate coefficient are expressed as functions of
the headcut erodibility index. This index was adopted from work done in South
Africa on material excavability, and that work in turn was built on work in
Scandinavia on tunneling. The curves shown here are those developed from data
collected over a 10 year period from field spillways on flood control reservoirs.
The Corps also used the approach to analyze data from some of their spillways and
came up with slightly different curves. We are presently working with Corps
researchers in Vicksburg to reanalyze all of our data to see if we can refine these
relations.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT
Advance Component
HEADCUT ERODIBILITY INDEX, Kh

Ms = material strength number
Of the earth material,
Kb = block or particle size,
Kd = discontinuity or inter-
Particle bond shear
Strength number, and
Js = relative ground structure
Number.

The index itself is a measure of the overall strength of the material mass. In the interest of
time, I'm not going to go over the details, but references are provided in the materials we
made available for the workshop.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT Advance Component
Multiple Materials

Material 1
Material 2
1 2 3 4 5 6 7 8
INLET CREST EXIT

Of course, spillways never exist in a single material, so use of the relations requires
determination of a representative value of headcut erodibility index for multiple
materials. Since the index lives in log space, the form of averaging used is

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PHASE 3: HEADCUT Advance Component
Multiple Materials

Kh = e EhiIn(Khi)/Ehi
hi = the thickness of material i, and
Summation is carried out over all materials exposed on the face

A depth weighted log averaging scheme. This has been found to work surprisingly
well.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

ITERATIVE MODEL APPLICATION
Failure Initiation

Material 1
Material 2
1 2 3 4 5 6 7 8
INLET CREST EXIT

It is also necessary to apply the method iteratively to determine the worst case
condition for location of headcut formation. It is not immediately obvious whether
a headcut formed early in the flow at the end of the exit channel will pose a greater
or lessor risk of breach than one formed later near the crest. If material 2 happens to
be a sand lense, it may also be that the headcut that exposes that material the most
rapidly will be the one posing the greatest risk.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

ITERATIVE MODEL APPLICATION
Headcut Computations

Material 1
Material 2
1 2 3 4 5 6 7 8
INLET CREST EXIT

On the other hand, if material 2 is a rock it may be that a headcut following the
upper surface of the material will move more rapidly than one penetrating into or
through that material. All of these scenarios must, therefore, be evaluated. In the
present model, they are evaluated one at a time as if that headcut were the only one
present.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RESEARCH NEEDS
Headcut Based Model

* Phase 1 - Vegetal cover failure
Refinement of upper limit of application (maximum gross stress)
Improved analysis of brushy vegetation

Let me begin the discussion of research needs in the context of the Sites erosion
model. And I'll begin by noting that Sites represents a first attempt at quantifying
the overall process for field application, and there is no part that couldn't be refined;
And we recognize that it does not apply to every spillway problem.

In terms of the phase 1 processes, there are a number of areas that could be
improved, but the model is probably consistent with the extent that we normally
have information to describe the condition of the surface. Areas where advances
could be made include improved determination of the upper limit of applicability of
the erosionally effective stress relation; that is At what gross stress does the
vegetation begin to experience damage directly?; and improved analysis of the
effects of brushy vegetation. The fact is though, that phase 1 plays an important
role only for relatively low heads and relatively erodible materials, so the mileage
were going to get from refinement here is somewhat limited.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RESEARCH NEEDS
Headcut Based Model

* Phase 1  Vegetal cover failure
Refinement of upper limit of application (maximum gross stress)
Improved analysis of brushy vegetation
* Phase 2 - Concentrated flow erosion
Detachment threshold values for intact rock
Detachment rates for large rock materials

Phase 2 is usually the most important for spillways with rock materials near the
surface of the spillway. The present model implicitly assumes loose material (based
on diameter only) and will often be over-conservative. The model needs to be
refined. This could be done using either stress or energy approaches, but will
require data that is rather scarce.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RESEARCH NEEDS
Headcut Based Model

* Phase 1  Vegetal cover failure
Refinement of upper limit of application (maximum gross stress)
Improved analysis of brushy vegetation
* Phase 2  Concentrated flow erosion
Detachment threshold values for intact rock
Detachment rates for large rock materials
* Phase 3 - Headcut Advance
Refine headcut erodibility index
Gather additional threshold and rate data for rock

In terms of the downcutting portion of phase three, all of the considerations of phase
2 apply, plus the need to better tie the downcutting and advance parameters together
to avoid inconsistent data.

The headcut erodibility index itself needs refinement. USDA is presently working
on refining our means of estimating it in the never-never land between soil and
rock. However, more fundamental work on the index itself is needed. As it
presently exists, it was simply adopted from excavability applications. The
processes are similar, but not identical. The index was named as it is so that future
modification would be possible without confusion with other application related
indices.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RESEARCH NEEDS
Headcut Based Model

* Phase 1  Vegetal cover failure
Refinement of upper limit of application (maximum gross stress)
Improved analysis of brushy vegetation
* Phase 2  Concentrated flow erosion
Detachment threshold values for intact rock
Detachment rates for large rock materials
* Phase 3 - Headcut Advance
Refine headcut erodibility index
Gather additional threshold and rate data for rock
* General
Expand computational model to include breach

A more general need that has been identified is to expand the model to include
breach computations in such a way that we could account for the ability of changing
geologic materials to stop complete breach. If you think about what is involved,
that is no small task. We could also expand to talk about three dimensional
geology, tailwater effects, air entrainment effects, etc., but those would require
substantial advances in material mapping and description before inclusion in a
general application model could be justified. Some of these issues are addressed in
the publications included in the list provided to the workshop.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RESEARCH NEEDS
Earth Spillway

* Identify Failure Modes
* Develop consistent means of evaluating uncertainty

The three phase model with headcut advance to breach represents a major
portion of the earth spillways observed to have experienced damage. However, it
does not represent all conditions. For example, this spillway in volcanic rock
eroded due to abrasion in areas of reverse flows where potholes were developed.
This type of erosion is not addressed at all in the Sites Model. Likewise, long flat
sloped spillways in material where sediment transport is an issue are not properly
analysed by the Sites model, because Sites assumes detachment limited conditions
and movement of the detached material out of the immediate area.

We could go on much longer with this, but I'll stop with this one last comment. All
of the available models are simplified and we seldom know exactly what materials
will be exposed during the erosion process. This uncertainty needs to be evaluated
along with the uncertainty related to the flow conditions. Some work is going on
now at Vicksburg in this area, but spillway erosion analysis is still in its infancy.
We still have much to learn.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 6:
Spillway Foundation Erosion

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Dam Safety Workshop
Spillway Foundation Erosion

James F. Ruff, Ph.D., P.E.
Department of Civil Engineering
Colorado State University

Spillway Components

* Entrance channel
* Crest/control structure -- ungated, gated
* Conveyance -- chute, conduit, tunnel, or combination
* Terminal structure -- stilling basin, flip bucket, plunge
pool
* Incidence of spillway foundation scour is relatively low
- Cause generally result of discharge greater than design.
* Foundation undermined by scour from downstream
- Major damage
- Time constraints
- High repair costs
- Reservoir operations affected by foundation scour

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Gibson Dam

June 8, 1964
20 hour duration
1 m overtopping

1979 Modification
$1,240,000

Colorado State University
Experimental overtopping and
foundation erosion facility

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Scour Prevention & Research
Focus on Depth, Rate

Spillway models - component testing
Small scale
estimate scour depth and location
pressures on chute and in stilling basin

Foundation erosion by plunging jets
Near-prototype scale
gravel bed
simulated rock

Foundation protection
concrete blocks
riprap chute and toe

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Scour of simulated fractured rock

Spillway riprap
Protection

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Prototype foundation scour data

1.OOE.01 I.WE*W 1 .OOE*Ol 1.00+02 1.00E*03 1.00E*04
Erodibility Index

CSU Foundation scour depth equation for non-cohesive material
and simulated fractured rock

Y/yc 3.111 (Vi/gbi)007/[(TW/cos 0)/bi]0.39 (w/g b1)1.13 (6.5)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

CSU Foundation scour depth equation for non-cohesive material
and simulated fractured rock

DFE
WE-model
DFE Block
Identity
Id + 25%
Id- 25%
2.0 1.5 1.0 0.5 0.0 
Predicted Y (m)
0.0 0.5 1.0 1.5 2.0 - Measured Y (rn)

Universal design equation for overtopped riprap

Comparison of experimental data
With Design Equation (Log-Log scale)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways 83

Research needs on dam spillway
foundation erosion

* Evolution of velocity and air concentration profiles along the 
jet, namely at the impact with plunge pool free surface.
* Lined plunge pools - slabs and foundation drainage design
criteria.
* Mechanism of rock erosion due to the spillway operation and
Development/improvement of physically based analysis
models.
* Prototype data collection for the improvement of scour
prediction formula.
* Scour depth and shape evolution versus time of operation and
hydraulic / geologic parameters.
* Evaluate effects of jet entry angle on plunge pool
performance and scour.
* Investigate near-prototype riprap protection at additional slopes.

The end

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 7:
Dam Overtopping Protection Technologies
State of Practice and Research Needs

FEMA Workshop - Issues. Remedies and Research Needs Relating to Service and/or Emergency Spillways 85

DAM OVERTOPPING 
PROTECTION TECHNOLOGIES
STATE OF PRACTICE AND RESEARCH
NEEDS

Kathy Frizell
US Bureau of Reclamation
Water Resources Research Laboratory
Denver, CO

Overtopping Technologies

* Earthen embankments
* Grass covered earthen
embankments
* Geotextiles &
Membranes
* Gabion/Reno
mattresses
* Riprap
* Concrete blocks
- Cable-tied,
interlocking,
overlapping
* Soil cement
* Reinforced concrete
slab
* RCC
- Smooth
- Rough lifts
- Formed steps
* Stepped spillways
over embankment or
concrete dams
- Formed RCC or
reinforced concrete

86 FEMA Workshop  issues, Remedies and Research Needs Relating to service and/or Emergency spillways

Introduction

* Many options
* Overtopping protection methods all have
hydraulic criteria that must be met
* VERY brief discussion of each method
* Design guidance or limitations
Based upon testing or field performance
* Maintenance requirements
* Research needs

Hydraulics of Overtopping

Subcritical Flow Supercritical Flow Supercritical Flow Subcritical Flow

Increasing Velocity & Decreasing Depth
Increasing Velocity & Decreasing Depth
Constant Velocity & Depth
Turbulent Flow

Reservoir Critical Depth
Potential Subatmospheric Zone
Theoretical Nappe Profile
Normal Depth
Hydraulic Jump on Slope
Hydraulic Jump At Toe of Slope
Tailwater
Embankment

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Earthen or grass lined embankments

* Cannot add anything to Darrel's
discussion!
* Grass covered limitations:
Overtopping up to 1.5' of head, short
duration, velocities less than 12 ft/s.

Geotextiles & Membranes

* Protective fabric is placed over compacted earth
w or w/o a filter
* FHWA tests: Enkamat w/asphalt, 2:l slope, 6'
high dam, V= 13 ft/s; Geoweb, V=9.5 ft/s
* USBR field test: 36 mil Hypalon geomembrane,
6: 1 slope, 19' high dam, V=10-25 ft/s
* Design & Construction
- Must be placed over smooth surface
- Must be anchored at crest, toe, sides
- Must be covered for durability
- Seams must overlap

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Rock or Reno Mattresses

Performance  FHWA & CSU testing
CSU testing
* Mattresses placed flat over
slopes up to 2:1 with 3-6"
size rock
* Design based upon shear
stress of flow and critical
shear stress of mattress
* Thickness 1.5*max rock
size
* Max Velocity 24 ft/s
* Filter required
* Case 3 Is max deformation
allowed
* Groutlng helps stability
* Anchoring essential!

Gabions

* Gabion baskets are filled with 4-8" rock and
stacked leaving a stepped surface on slopes of
2: 1 or greater
* Used where mattress criteria is exceeded; steeper
slopes & higher velocities
* Performance - Peyras model testing
Dam ht. up to 3.3', slopes of 1:1, 2 : l & 3:1
gabions stacked from i) to 7 steps high, =h cfs/ft, v= 20 ft/s
Design equation based upon slope, ht., q, allow
determination of depth at the gabion slope toe for
stilling basin design
* Manufacturer's: Maccaferri (w/design software) &
Terra Aqua

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Riprap
* Protection is achieved by placement of a
designed rock size over an embankment
slope or designed spillway channel
Application to fuse plug erosion rates and
unintentionally overtopped riprap embankment
slopes
* Design criteria for riprap size & layer
thickness for steep slopes using existing
experimental data (including ARS) and
data from CSU test program

Test Facility
* 10' wide, facility q=16
cfs/ft
* Dumped over angle
iron & 8" bedding
* Open frame or down
full slope with toe
berm
* Rock sizes tested:
D50= 15.1", D50=25.8"
over previous,
D50= 10.7" full slope &
toe (photo)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Flow Conditions, Measurements,
Failure

* Measured Q, V,, d
* Velocities in each layer
constant
Flow beneath the rock
surface for 2:1 slope
* Failures (bedding exposed):
D50= 10.7",q=2.2 cfs/ft
D50= 15.1, q=2.4 cfs/ft
D50= 25.8, q=10 cfs/ft
15" rock
10.7 rock
1.5 cfs/ft
Total failure
10.7" rock

Riprap sizing chart based upon q, slope and rock properties  no SF

1 0.1 0.01 0.001
D50 Cu(0.25)
0.001 0.01 0.1 1
Unit discharge q (m2/s)
S = 0.02 (NRC/CSU)
S = 0.10 (NRC/CSU)
S = 0.10 (ARS)
S = 0.20 (NRC/C3U)
S = 0.40 (AR3)
S = 0.5 (U3BR/C3U)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Riprap Performance

* Design chart and equation provides stable
stone size as a fun 8 ion of discharge, stone
gradation, and slope.
D50Cu0.25 0.55(qf)0.52S0.75(sin/2.65cos 1)cos tan sin))
* Layer thickness is a function of discharge,
interstitial velocity, stone size and slope.
Vi/(gD50) - a 2.48Cu a2.22S0.58
* Interstitial flow for 2:1 slope, flow depth may
exceed riprap layer thickness for slopes < 4: 1
* Historically, min of 2D50 or D100.
* Toe more stable than slope.

ACBs

* Concrete block systems widely varied
geometries, test programs, applications
* Cable-tied
Weight, shape, filter, cabling for stability
* Interlocking
- Weight, shape, interlocking, filter, careful
placement for stability
* Overlapping
Shape, filter, maintaining overlap for stability

92 FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency spillways

Cable-tied Concrete Block
Tested ArmorFlex Tapered Unit

17.4 15.5
TOP VIEW
FLOW DIRECTION
0.5
4.75
SIDE VIEW
Wt. = 66 lbs 
Thickness = 4.75"
Forces on block evaluated under high
velocity lnstallatlon over compacted earth
in CSU flume facility

ArmorFlex Mat Delivery 

FEMA Workshop - Issues, Remedies and Research Needs Relating to service and/or Emergency spillways

Strahl Lake Dam, Indiana, DNR
* Cable-tied mat
sections
* Close up of cable
tie section

Strahl Lake Dam

* Crest construction
* Completed system
* Grass covered system

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Armortec Tapered Cable-tied Block
Design Factors & Performance Data

* Must anchor the crest and provide flow barrier,
* Drainage system enhances performance and is
recommended.
* Successfully withstood test with 16- ft-high, 2:1 sloping
embankment
- q-20 cfs/ft, 4' of head, V=26 ft/s, shear stress= 25 lbs/ft2
* Use maximum velocity and flow depth to determine product
needed.
* The hydraulic jump should occur on an armored or nonerodible
surface to prevent headcutting and undermining of
the ACB layer.
* Needs uni-directional flow over the embankment surface.
* Make sure the specified product has been evaluated under
high-velocity testing conditions with steep slopes.
* Maintenance:
- Keep the protected slope and toe clear of woody vegetation.
- Prevent vandalism or removal of block units.

Interlocking Concrete Blocks
* Conlok, Tri-lock, Armortec, others
* Testing
- FHWA/Armortec/SAF
* Design guidance - Generally not as good a product for
overtopping protection as other block systems.
* Construction - Critical feature of interlocking block
systems exposed to high velocity flows. ANY portion of
the block edge exposed to flow impact can fail the
system. Install where base surface has NO
discontinuities.
* Maintenance
- Keep the protected slope and toe clear of woody
vegetation.
Prevent vandalism or removal of block units.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Overlapping Tapered Concrete Wedge
Blocks Performance Testing (Armorwedge)

50-ft-hlgh, 5-ft-wlde, q= 32.2 cfs/ft, blocks placed over angle
with gravel filter, anchored at 3rd points on slope, held at toe.

Top slope, 4<hs/1<6, 2.8% vent area on face, min thickness 2"

Forces Acting on the Overlapping
Tapered Wedge Block

* Inherently stable
- Impact on tread &
Relief of uplift at low
pressure zone by
aspiration through
vents
* Analyzed forces as sum
normal to slope

FLOW >
Separation Zone
Impact Pressure Zone
Vents
Uplift Pressure
Block Weight
Drainage Layer

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Overlapping Tapered Concrete Block
Performance Data

* Successfully withstood maximum
flow from test facility:
- q = 32 cfs/ft, overtopping depth ~6.5
ft, velocities > 40 ft/s
- Friction factor, f=0.08
- Mean air concentration, C=0.39
- Failed only after block was pried out of
the matrix using 600 lbf

Soil Cement

* Many designs protecting embankments
with soil cement either rolled flat over the
slope or in stepped lifts. (Freese & Nichols
experienced designers)
* Similar to RCC except not the same mix
strength
* Hydraulic characteristics the same as RCC
and defer the discussion to then.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Reinforced Concrete Slab

* Concrete slab designed over an
embankment or rock-fill dam
- A.R. Bowman Dam (U.S.) feasibility design (full
coverage)
- Crotty Dam - Australia- spillway section
* Critical design features:
- Drainage system
- Preventing slab cracking and offsets
- Designing for influence of tailwater and jump
over slab

RCC

* Revolutionized dam rehabilitation &
new dam construction
- Rejuvenated the issue of stepped
spillway design
* Ken Hansen will discuss

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Stepped Spillways - Formed RCC or
Reinforced Concrete

* Located over entire or a portion of the dam or on
a separate abutment
- Discuss embankment dam slopes as that is typically
what is thought of when referring to "overtopping".
* Step ht typically driven by construction
techniques
* Useful for energy dissipation
* Test programs - incredible number
* Design guidance - controversial
* Maintenance:
- Ensure concrete is in good shape and cracking
Minimized

Large-scale Flume Facility - 2-ft-high
Steps 
Nappe flow - q=5 cfs/ft

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Large-scale Flume Facility - 1-ft-high
Steps

Skimming flow  q-15 cfs/ft
Embankment Slope Step Designs
* 0ptimum step ht.
h/dc~0.3
* Use alr concentration
& velocity data to
determine energy
remaining in the flow.
d = (1- Cmean)Y90
* Assumes uniform flow
is attained.
uw = qw/d
* Shows that friction
factor is nearly
constant over a range
of step ht. to
hydraulic diameter.
F = 2 g sin a Dh/U /w

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Hydraulic Design Considerations

* Calculate distance down the slope and depth at
the aeration inception point. Cmean = 0.23
* Determine mean air concentration down the slope
* Training wall height equal to the Y90 = f(Cmean)
depth, friction factor)
* Energy at toe= f(dam ht, slope, head, friction)
* Design stilling basin using water depth and
velocity.
* Cavitation damage has not occurred with designs
to date, but might need to be considered for large
q.

Design Criteria
* Debate: test facilities and data acquisition methods ha*
dramatically varied. Which is correct?
- Jorge Matos, IST, Portugal
- Robert Boes, VAW, Zurich, Switzerland
- Stephanie Andre, EPFL, Lausanne, Switzerland
USBWCSU
- Hubert Chanson, University of Queensland, Australia
- Many other site specific studies added to the mix
* Debate: What presentation method of design criteria is the
best? Those based upon:
- Friction factor
- Mannlng's equation
- Residual energy computations based upon;
* Continuity
* Uniform flow equations
* Both from various measurements of aerated & non-aerated flow from
model and prototype tests

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Stepped Spillway Research Needs

Development of peer reviewed manual for stepped spillway
design that considers all techniques and meets requirements of
practicing engineers
* Needed for low and high dams with high q, uniform & nonuniform
flow regions, flatter and steeper slopes.
* Possibly develop a chart of a ratio V3/Vt, versus total head
for various sloping stepped spillways.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 8:
Roller Compacted Concrete Overtopping
Protection for Increasing Spillway Capacity

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Roller Compacted Concrete
Technology

Ken Hansen
Schnabel Engineering
Associates, Inc.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

OCOEE NO. 2 DAM  TENNESSEE

Roller compacted concrete
Riprap face choked with concrete
Drainage pipe
Rockfill timber crib
Crib timbers removed
Riprap

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Ocoee #2 dam

Ocoee #2 dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Ocoee River 1996 Olympic
Kayak Course

Brownwood Country Club Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Brownwood Country Club Dam

TO REMEDY A 
HYDRAULIC
DEFICIENCY

Breach The Dam
Increase Storage
Increase Spillway Capacity
Overtopping Protection
Combination 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

New Roller
Compacted Concrete
Existing Embankment
Ground Line
6 Dia.
Toe Drain

BROWNWOOD COUNTRY CLUB DAM-TEXAS

RCC

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Brownwood Country Club Dam

Brownwood Country Club Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Brownwood Country Club Dam

Spring Creek Dam  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways
Spring Creek Dam  CO

DESIGN
OBJECTIVES

Life: 50  100  1000 yrs
PMF Interval? 
Event Duration
Peak Shifting
Delay Failure
Factor of Safety

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Pasture Dam  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Pasture Dam - CO 

Goose Pasture Dam - CO 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Pasture Dam - CO 

Goose Pasture Dam - CO 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Pasture Dam - CO 
T
Goose Pasture Dam  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Lake Dam Soil Cement Placement
Maximum Section

Goose Lake Dam  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Lake Dam  CO

Goose Lake Dam  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Goose Lake Dam - CO 

Standley Lake Mod.  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

RECOMMENDED
RCC DESIGN

Small Volum Projects
Little F/T: 2100 psi @ 28 days
min. (i.e., approx. 250 lb/cu yd)
F/T Zone: 3000 psi @ 28 days m
(i.e., approx 325 lb/cu yd)

Leyden Dam Rehab.  CO

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Leyden Dam Rehab.  CO

Aggregate

Good Quality
Local Availability 
Minimum processing
MSA about 1.5" (38mm)
40% passing #4
4-8% passing #200
Cement vs Aggregate Cost

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Douthat Dam Rehab  VA

Douthat Dam Rehab  VA

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

PEE PEE CREEK

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 9:
General Discussion - NRCS
Designs and Research Needs

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

USDA NRCS
NATIONAL WATER MANAGEMENT CENTER

Dam Safety Workshop
Denver, Colorado
August 26-27, 2003

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NWMC Functions

* Direct Technical Assistance
* Consultation and Training
* Watershed Plan Development and Review
* Linkage to Other Specialists

NRCS Hydrologic Criteria

Maximum Frequency of Use for Vegetated
Auxiliary Spillway
(Storage above the Principal Spillway)

Low Hazard - Class (a): 25 year Precipitation to
50 year Precipitation
Significant Hazard - Class (b): 50 year Precipitation
High Hazard - Class (c): 100 year Precipitation

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Hydrologic Criteria

Auxiliary Spillway Design Hydrograph

Low Hazard - Class (a): 100 year Precipitation to
(P100 + 0.12(PMP  P100))
Significant Hazard - Class (b): (P100 + 0.12 (PMP  P100))
High Hazard - Class (c): (P100 + 0.26 (PMP  P100))

NRCS Hydrologic Criteria

Freeboard Design Hydrograph

Low Hazard - Class (a): (P100 + 0.12 (PMP  P100))
to (P100 + 0.40 (PMP  Pl00))
Significant Hazard - Class (b): (P100 + 0.40 [PMP  P100))
High Hazard - Class (c): PMP

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Principal Spillway

NRCS Principal Spillway

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Principal Spillway

NRCS Vegetative Auxiliary
Spillway

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Vegetative Auxiliary
Spillway

NRCS Vegetative Auxiliary
Spillway

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Straight Drop
Auxiliary Spillway

NRCS Straight Drop
Auxiliary Spillway

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NRCS Roller Compacted
Concrete Auxiliary Spillway

Research Needs

* Erosion Model for Breach Determinations
from Dam Overtopping
* Peak Discharges from Erosion Breaches
* Stilling Basin Design for RCC Stepped Spillways
Revised Rainfall/Frequency Maps

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

NWMC
http://wmc.ar.nrcs.usda.gov

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 10:
Spillways - An Owner's Perspective

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillways
Owners Perspective

Spillways
* PMP/PMF
* Old Story
* But it is time to take another look!

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillways - Recent History
It appears that the upward ratcheting of
spillway capacity has slowed at least a
little

* Phase I (1978) identified over 60,000 +
dams, most were non federal, earth
dams with "inadequate" spillways

The Problem

Because most of the 60,000 dams are privately
owned dams, many can not afford to meet the
spillway criteria currently required

* A few owners that can comply (BUREC, FERC
Regulated Dams, and Large Utilities) have the
Funds most others do not

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillways

* Most of the problems with private dams have
been addressed except in the area of
spillways
* Billions have been spent, storage has been
Lost and still there are many dams that do
not have "adequate" spillways
* The primary driver is the precipitation derived
from HMRs  the PMP

PMP/PMF - WHY?
* The National Weather Service (NWS)
introduced the PMP/PMF primarily for
COE and other federal dams
* This technology was transferred to
private dams (first large then small
dams) with little thought about the
increased costs to the private sector

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Problems with Using HMRs

* Infrastructure costs are simply too high and so
states and local governments have invented
creative ways to work around the numbers;
* Incremental Damage Studies
* "Site Specific Hydrologic Studies
"Grandfathering
* Changing Precip. requirements for classes of
dams
* Changing definitions of dam classifications
* Risk based analysis

More Problems with HMRs
* Data that supports the HMR findings is often
lost or can not be supported by the record
* The CORE or the BUREC have not found
the "need" or the money to further the
science of extreme precipitation events
* The procedures used in the HMR are not
well understood and are considered by most

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Questions
* Was and is the NWS the right agency to
plant the PMP seed that resulted in so
many spillways to be inadequate?
* After 25 years, do we need to take
another look at why we need "zero" risk
when it comes to spillways?

More Questions
* With new techniques and computer models that
have been developed in the past 25 years, should
new methods and criteria be developed and
instituted (site specific)
* With the variety of "state by state" criteria, why
should people in one state be more or less
protected than other people in another state? Isn't
there a need to apply the criteria uniformly?
* Is a 5,000 or 10,000 year storm large enough?

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Proposal

Have National Academy of Science
(Engineering) or similar group:

Re-review the idea that the PMP level
of storm event vs need to protect the
public at all costs and risks

Proposal (cont.)

* Develop a new techniques for the PMP/PMF
to be used nationally by all states
* Develop new computer models that are
simple to use and understand, easy to
update with new precipitation data
* Keep it simple and keep it cost effective for
Owners

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 11:
General Discussion - Consultant's
Spillway Design and Research Needs

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Hydraulic Structures Technical Committee

To promote and/or advance research, analysis, design, construction,
operation and maintenance of state-of-the-art methodology associated with
hydraulic structures.

To accomplish this purpose, the committee proposes and organizes task
committees and/or subcommittees to complete projects which advance the
science. In addition, the committee promotes the technical exchange of
ideas through sponsored sessions at conferences, publications of reports,
papers, and monographs, and interaction with other professional and
technical societies.

http://www.wadepmoore.com/HSTC/

Hydraulic Structures Technical Committee

Current Membership

* John Hite Waterways Experiment Station
* Bruce Muller USBR Technical Center
John Finnie University of West Virginia
* Bruce Brand FERC
* Kevin Nielsen Carroll College
Kerry Robinson USDA - Agricultural Research Service
Rick Voigt Carroll College
Walt Heyder Polaris Group
* Mike Buecther Parsons Brinckerhoff Quade and Douglas
* John Laboon USBR Technical Center
* Wade Moore Montgomery Watson Harza
* Yifan Zheng Bechtel
* Richard Stockstill Waterways Experiment Station

USBR Technical Center

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillway Expansions by Harza

Cushman I 1990 Conventional Spillway
Brule 1991 Fuse Plug
Ponca 1992 Overtopping - RCC
He Dog 1993 Conventional Spillway
Blue Ridge Dam 1994 Conventional Spillway
Boney Falls 1994 RCC Fuse Plug
Bald Hill 1997 Overtopping - Conventional Concrete
Devil's Gate 1999 Conventional Spillway
Big Dalton 2000 Modify Outlet Works 
Granite and Crystal Dams 2000 Fuse Plug 
Middle Branch 2000 Overtopping - RCC
Overtopping  RCC

Dam Failure Analysis

* Develop 1-0 Unsteady Flow Model of System
* Use FERC criteria to "control" outflow from reservoir
1:1 Side Slopes
2h-4h Breach Width
0.1-1.0 hour Failure Time
Failure at Peak Water Elevation
* Perform Sensitivity Analysis
* Perform IDF Analysis
Largest Inflow that does raise water levels d/s more than 2 feet

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Dam Failure Analysis

Water Surface Profiles   PMF
Station (ft)

Dam Failure Analysis

Time (hours)
650

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Research Needs

* Overtopping Protection - economics of dab vs RCC
* Rip-rap stability - dumped vs hand placed
* Fuse Plugs - speed of erosion, trigger mechanisms, smaller sizes
* Fuse Gates - ice, debris, seals
* "Single" Use Spillways - allowable damage and repair
* Small Spillways - rock chutes, etc.
* Exceeding Design Head - damage prediction
* Conventional Chutes - converging walls, supercritical transitions
* Stepped Spillways - step size and shape vs head loss

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Research Needs

* Overtopping Protection - economics of dab vs RCC
* Rip-rap stability - dumped vs hand placed
* Fuse Plugs - speed of erosion, trigger mechanisms, smaller sizes
* Fuse Gates - ice, debris, seals
* "Single" Use Spillways - allowable damage and repair
* Small Spillways - rock chutes, etc.
* Exceeding Design Head - damage prediction
* Conventional Chutes - converging walls, supercritical transitions
* Stepped Spillways - step size and shape vs head loss

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 12:
Vegetated Earth Spillways - Inspection,
Maintenance, and Monitoring

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Vegetated Earth Spillways
Inspection - Maintenance
&
Monitoring 

Denver, CO
August 26-27,2003

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

OUTLET SECTION  EXIST. AUXILIARY SPILLWAY

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

About 2.5 of flow with little or no damage

Well maintained dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillway Looks like it has been well maintained

Tire Tracks

Equipment used for maintenance destroyed vegetation

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Trail develops into a major erosion problem.

Erosion in Spillway

Can you see the dam?

Road Up the Spillway

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Other uses  Trailer in spillway used for a home site

Hp on spillway = 0.5

Standing in entrance of Aux.
S/W looking at front slope of
Dam  good vegetation

Mud line

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Standing in entrance of Aux. S/W
Looking upstream  good vegetation

Vegetation in crest no good

Hay bales in control section

Standing in entrance to Aux. S/W looking downstream

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Almost no vegetation

Standing in control section looking downstream

Control Section

Standing in Aux S/W looking upstream

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Road

Standing in Exit Channel of Aux. S/W looking upstream

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Hickory Creek Site 11  Hay feeding on control section, cattle working pens in exit section

Vegetation - wrong kind

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Vegetation  when was the last time the spillway was mowed?

High Hazard Dam

Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

High Hazard Dam

Same Car and House

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Dam overtopped about 0.5 and the spillway had about a 5.2 Hp on it.

5.2 Hp on crest of this spillway  little or no damage

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Same spillway after the flow event. Minor damage.

Damage to dam from overtopping  about 0.5

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Homogeneous fill??

Spillway with debris from flow event and vegetation

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Erosion in spillway from a flow event

More erosion from a flow event. Note maintenance and vegetation good.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Headcut erosion from flow event.

The End

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 13:
Earth Spillways - State of Practice and
Research Needs

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Spillway Design 101

* Determine routed discharge flow
* Size channel for desired flow
- Broad Crested Weir (Q = c L H 3/2)
- Manning's equation
- HEC-RAS (HEC-2)
* Check channel flow velocity
- NRCS Bulk length procedure (SITES)
- HEC-RAS
* Armor (concrete, rock) or enlarge

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Bulk Length / Sill Walls
-soil type
-time of flow
-depth of wall/ width

Frenchman Creek Burgess #1

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Discharge co-efficient

Q= c L H3/2

What is correct value for "c";
-broad crested weir? (approx. 2.6-3.1)
-Uniform flow using Manning's eq.?
-Tailwater analysis -> C = approx. 1.5 - 4.1 !!

C = 2.5

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways
C = 4.0

Ice/Snow blockage
- snow depth
- melting/clearing

Design to keep spillway open despite snow cover?

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Precipitation in High Mountain Regions

There has been some research to date
suggesting that high mountains, and
orographic effects do not correlate with
published HMR data (Jarrett). Other
research indicates "rain shadow" effects
(Henz, Tomlinson).

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Research Needs:

Design criteria for:
- Flow capacity; C factor, bulk length
- Sill wall; depth, spacing
- Headcutting
* Ice/ Snow blockage, and melting
* HMR design indices for orographic
Effects

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 14:
Issues and Research Needs Related to
Hydraulics for State Regulated Dams

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Issues and Research Needs
Related to Hydraulics for State
Regulated Dams

BY
Francis E. Fiegle II, P.E.
Georgia Safe Dams Program
FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Issues and Research Needs
Related to Hydraulics for State
Regulated Dams
States regulate over 90% of the dams
listed on the National Inventory of
Dams.

State Survey 

30 states responded
* Types of spillways? 
* PVC siphon spillways?
* Ice and snow effects on hydraulics?
* Skimming flows on stepped spillways?
* Questions about hydraulics of spill ways?
* Adequate training?
* What are the issues?

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Siphons

* Hydraulics for multiple intakes
* Hydraulics for each pipe
* Maximum height limitations
* Maximum pipe size
* Material Types
* Joint integrity

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Ice and Snow
* Hydraulic changes due to ice
* Cost effective designs to minimize ice jams
and icing impacts
* Ice/snow removal without site visits (
especially small dams)

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Drop Structures
* Slugging flows in deep conduits
(prevention)
4 Loading of pipddrop structure due to
slugging flows
Rational approach to air demand &
minimum air pressure in outlet pipes
:b Deflector plates in drop structures ( are
they necessary)

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Stepped Spillways (RCC)
* Changing hydraulics due to weathering of steps
* Skimming flows at high volume flows
* Hydraulic Jumps in stilling basins (Have
we forgotten lessons learned in concrete
chute design?)
* Cracking in steps/stilling basins

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Looking upstream @ center towards ogee crest from downstream

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

At center looking downstream

Concrete Blocks -
* Performance during extreme floods
* Debris flows
* Long term material performance

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Hydraulic Coefficients

* Overstated coefficient capacities
* Better software
* Realistic and relevant evaluations

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Irregular Spillway Shapes

* Geometric shape evaluation
* Rock lined/rip rap lined channels
* Rock channels
* Man made rapids versus fish passages

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Miscellaneous

* Corrugated metal pipe life
* Overtopping of earth dams
* Rip rap / concrete drop structure design
* Flash boards that do not fail
* Application of earthquake loading forces
with hydraulic and other loading conditions.
When?

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Research Results Need to be
Relevant and Reliable

The results need to be proven in the
field in long term applications. Small
dam owners do not have the financial
capability to do the same upgrade
twice.

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Issues and Research Needs
Related to Hydraulics for State
Regulated Dams

Questions?

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Presentation 15:
Concrete Spillway Repairs

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Spillway Repairs

Jim McDonald
Consulting Engineer
Clinton, MS

Premature Repair Failures

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Repair/Substrate Compatibility

Definition - The capacity .of two or more entities to
combine or remain to together without undesirable
aftereffects: mutual tolerance.

Incompatible

Compatible

Effect of Bond Breaker at Interface

- Bonded Interface
- Bond Breaker
Stress, psi
Compression
Tension
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Replacement concrete age, days

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Effect of Restraint

Repair Overlay
New Construction

Performance Criteria 
Cement-Based Materials 

12 Repair Materials
Field Performance Tests 
Laboratory Tests
Correlation
Dimensional Compatibility

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Performance Criteria
Laboratory Tests

* Drying Shrinkage
-Unrestrained
-Restrained
* Modulus of
elasticity
* Creep
* Thermal expansion
* Strength

Performance Criteria
Field Tests

* 3 exposure sites (FL, IL & AZ)
* 3 repairs with each of the 12 materials
* Conduct restrained shrinkage tests
* Monitor performance

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Field Exposure Tests
Relative Performance Ratings

6  Satisfactory
2  Marginal
4  Unsatisfactory

Drying Shrinkage
50% RH, 28 Days

Cementitious
Polymer Modified
Shrinkage, Millionths
0 200 400 600 1600 1800
1 2 3 4 5 6 7 8 9 10 11 12
Material numbers

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

28-Day Shrinkage & Field
Performance
Acceptable Materials

Strain, Millionths
0 100 200 400 500 600
1 2 3 4 5 6 7 8 9 10 
Relative field ranking

Tensile Strength Test Results
28 days

Cementitious
Polymer Modified
Tensile strength, psi
0 200 400 600 800
1 2 3 4 5 6 7 8 9 10 11 12
Material numbers

Range: 90-740 psi
Average: 390 psi

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Tensile Strength & Field Performance
Marginal and Unsatisfactory Materials
Tensile strength, psi
0 200 400 600
Diameter: 2 in. min
U/D 2.0- 2.5
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Relative field ranking

Performance Criteria for
Cement-Based Repair Materials*

Property Test Method Requirement
Tensile strength, min CRD-C 164 400 psi
Modulus of elasticity, max ASTM C 469 3.5 x 106 psi
Thermal coefficient, max CRD-C 39 7 millionths/deg F
Drying shrinkage, max ASTM C 157 (Modified)
28 days 400 millionths
1 year 1,000 millionths
Restrained shrinkage Ring Method
Cracks None < 14 days
Implied strain (1 yr), max 1,000 millionths
* http://www.wes.army.mil/SL/HPMS/bulletings.htm

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Laboratory/Field Correlation
Satisfactory Performance

Field Rank
Matl No.
Tensile Strength, (>400)
Modulus of Elasticity (<3.5)
Thermal Coefficient (<7)
Drying Shrinkage
Ring Test
28 Days (<400)
Peak (<1,000)
1st Crack (>14)
Implied Strain (<1,000)
1 1 1 451 2.8 5.8 178 366 6 667
1 4 348 3.8 8.3 201 703 140 560
1 11 390 5.9 7.6 339 641 14 810
4 12 742 3.0 9.3 293 634 None 0
5 8 215 2.7 9.2 305 1,109 8 1,222
5 9 323 2.7 6.9 429 9=877 23 955

HPM&S
High-Performance Materials and Systems Research Program

http:www.wes.army.mil.SL/HPMS/bulletins.htm
"Performance Criteria for Dimensionally Compatible Repair
Materials" (Jan 2000) 0.4 MB, PDF file
[Key words: cement-based materials, concrete repair,
drying shrinkage, performance criteria, tensile strength]

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Libby Dam

Libby Dam
Pneumatically Applied Mortar

Proportions
Cement 10 lb
Sand 40 lb
Water 4 lb
Retarder 9 ml

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Libby Dam
Mortar Gun 

* Easily assembled from readily available material
* Only a few critical dimensions
* Can be operated by personnel without extensive
Training
* EM 1110-2-2002, Evaluation and Repair of Concrete

Libby Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Research Needs

* Tools to reduce O&M costs and extend functional
Life of existing water-resource infrastructure
- Sustainable repair technology
- Innovative repair materials that satisfy compatibility requirements
- Underwater concrete repair
- Inspection techniques

Research Needs

* Reliable NDT equipment/procedures to evaluate gate anchorage systems
- Detect corrosion activity and determine rate
- Determine stress levels, particularly post-tensioned systems
* Materials and methods to mitigate ASR in existing mass concrete structures
* Capture corporate knowledge and promote technology infusion into the field

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Presentation 16:
Inspection of Concrete Spillways -
Gated and Uncontrolled

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Inspection of
Spillways

Gated
and
Uncontrolled

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Chutes, Tunnels, & Stilling Basins

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Inspection
Techniques

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Presentation 17:
Geophysics for Spillway and Seepage
Evaluation

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Geophysics for Spillway & 
Seepage Evaluation 

So what is Geophysics

The study of the earth (and other materials)
using non-intrusive measurements of
physical properties.

Some typical examples of parameters we measure are:

* Resistivity
* Seismic velocity
* Localized magnetic field!
* Gravity field
* Radar wave velocity & reflectance

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

How is Geophysics Helpful?

* Non-lnvasive "Screening " Tool
* Does not Generate Waste (Environmental)
* Supplements Subsurface Data Between Borings.
* Help Subsurface Characterization by Seeing the Big Picture
* Quickly Search for Specific Targets
* Trace What is Not Easily Seen (Water Seepage)
* In-Situ Estimation of Engineering Properties of Subsurface Earth Materials

Some of Our Common Tools

* Resistivity Sounding and Imaging (2-D & 3-D)
* Electromagnetics (EM)
* Ground Penetrating Radar (G P R)
* Magnetics
* Induced Potential (IP)
* Spontaneous Potential (SP)
* Seismic Techniques
* Microgravity

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

What Can you Do with Geophysics?

* Trace Seepage through 
Embankment Dams/Ponds
* Define Limits of Voids underneath Spillway Slabs
* Determine Shear Wave Velocities for Seismic Design
* Karst Investigations 
* Detect Abandoned Mines
* Map Voids and Sinkhole Potential
* Subsurface Stratigraphy
* Characterize Geologic Structure
* Determine Depth to Bedrock
* Determine Depth to Non-rippable Bedrock
* Map Contaminant Plumes
* Locate steel Reinforcing in Concrete Slabs
* Locate Underground Storage tanks (USTs)
* Define Limits of Abandoned Landfills
* Confirm Fractures in Bedrock for Groundwater Well Siting
* Assess Concrete Quality
* Monitor Vibrations from Blasting/Construction/Demolition
* Define GW Well Capture Zones in Fractured Bedrock
* Locate Buried Metallic Debris

Performing Geophysical Investigations

Investigation Design > Data Collection > Data Reduction > Analysis > Interpretation

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Object of This Presentation

NOT to teach the theory of geophysics;

RATHER, to provide examples where geophysics is used to provide valuable information

Example 1, Moores Creek Dam, Lexington, VA

Outlet Structure

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Sinkhole in downstream face above spillway conduit

Boil at Toe of Dam

Geophysical Investigation to Define Seepage Pathways

Complimentary
Geophysical
Techniques

* Self Potential (SP)
(measures voltages from water
moving through porous
medium)

* Two-Dimensional
Resistivity
(measures low resistivity
zones caused by increased
water saturation)

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Spontaneous Potential

Causes of SP Anomaly

Ground Surface
Fixed Electrode
Roaming Electrode
Electrical Potentials
Non-Polarizable Electrode

* Mineralization
* Geothermal gradients
* Bioelectric activity
* Varying electrolytic concentrations in ground water
* Geochemical variations
* Corrosion
* Changes in topography
* Telluric currents
* Streaming

Plan View of the Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Plan View of SP Results

Self Potential (milli-volts)

Resistivity Data Layout

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Electrical Flow Through Earth Materials

Resistivity Results

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Example 2: SP on Water, Chagrin Falls, OH

Seepage Through or Around Spillway?

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Through Embankment Adjacent to Intake

Example 3, Lake Logan, NC 
Sonic Analysis of a
Concrete Arch Spillway 

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Tomographic Analysis of the Sonic Data to Locate Poor Concrete Sections

Example 4, Concrete Spillway Slab

Finding Voids Under Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Ground Penetrating Radar (GPR)

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

GPR Results  Typical Voids

FEMA Workshop - Issues, Remedies and Research Needs Relating 
to Service and/or Emergency Spillways

Approximately 12 feet
Footing and Piles
Rebar
Potential Voids
Bottom of Concrete and Stone Subbase
Spillway with Shaded Areas Showing Voids and Areas with no Rebar in the Slab

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

GEOPHYSICS
* Will NOT solve every problem.
* Each method has strong and weak points, therefore often best when several complimentary methods used.
* Can be extremely useful and cost effective if used Properly to see the big picture, or to search for targets.
* Necessary to understand geophysical principles, geology, construction methods and design, and what the client wants in order to provide USEFUL interpretation and subsurface characterization.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 18:
Inspection, Maintenance, and Monitoring of Service and Emergency Spillways

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

MWH
Inspection, Maintenance and Monitoring of Service and Emergency Spillways
Daniel L. Johnson
MWH Americas

Current Condition
* Change in Mentality
* Attention paid to safety of dams
* Understanding of design events
* Owners awareness

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Levels of Experience
* Rarity of large flood events
* Denver snowstorm of 1913
* Big Thompson Flood of 1976
* South Platte Flood of 1965
* Events do occur and spillways are leading cause of failures

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Personnel Issues
* Inspection Knowledge Needed
* Failure modes
* Service spillways see more use than emergency spillways
* Emergency spillway may have never been used

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Inspection Issues
* Capability to meet design criteria
* Conditions and components for successful operation
- Located on abutment
- Located on dam
* Condition assessment
* Changes with time

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Inspection Issues
* Observation of operation
* Annual flood
* 5, 10 and 25 year flood
* Normal flows give indication of ability for successful operations
* Normal flows may be most critical for maintenance

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Maintenance
* Maintenance is typically not frequent
* Emergency spillway may be forgotten
* Repairs are necessary to maintain in as-designed condition
* Concrete
	- Movement, foundation erosion, toe and head erosion
* Earth
	- Slope protection, erosion of channel, abutments, toe, head
* Deleterious materials

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Special Issue
* Over-the-dam spillways need additional attention
* Frequent use as they are cost effective using RCC
* Induces new failure mode
* Increases frequency of emergency spillway usage

Monitoring
* Monitoring is needed
	- to estimate performance
	- to set a maintenance/rehabilitation plan
* Measurements of
	- movement, cracking, deterioration, aging issues
* Documentation of
	- surveys, photos, checklists and notes

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Data Usage
* Review of monitoring data
	- by personnel experienced and qualified
* When first gathered to understand current condition
	- as comparison to historic records for evaluating changes
* Reporting of results to owner and safety agencies

Conclusion
* Spillways constructed of engineered materials age
* Criteria may not be up to date
* Modern designs may have less robust components
* Inspection, maintenance and monitoring may be last hope

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Presentation 19:
Unlined Spillway Erosion Risk Assessment

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment 
Johannes Wibowo
Evelyn Villanueva
Don Yule
Darrel Temple

Photo of Tuttle Creek, KS

Unlined Spillway Erosion Risk Assessment
Problem Statements:
* Spillway erosion analysis encounters variable nature of geometry, geologic material and unpredictable flood events.
* Dam Safety Portfolio Analysis needs a tool to determine the probability of spillway damage.
Photo of Painted Rock, AZ

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Research Objectives:
* Develop a tool to assess the probability of damage on unlined spillway erosion * Develop a tool to prioritize unlined spillway/channel remediation projects
Photo of Saylorville, IA

Unlined Spillway Erosion Risk Assessment
Photo of DMAD spillway shortly after failure (1982)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Canyon Dam Spillway, Texas
Date: July 6, 2002
Flow: 66,000 cfs, 250 yrs flood
Duration: 12 days
Spillway Width: 1260 ft
Material: Limestone

Unlined Spillway Erosion Risk Assessment
Photo of Canyon Dam

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Risk Assessment
Process of Answering Three Questions
1. What can go wrong?
2. What is the likelihood it will go wrong?
3. What are the consequences if it does go wrong?

Unlined Spillway Erosion Risk Assessment
1. What can go wrong?
	* Local Scouring
	* Spillway Breach
	* Headcut Erosion
	* Dam Breach

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
2. What is the likelihood it will go wrong?
	* Uncertainty of Flood Event
	* Uncertainty of Material Parameters
	* Uncertainty of Performance of the Unlined Spillway

Unlined Spillway Erosion Risk Assessment
3. What are the consequences if it does go wrong?
	* Spillway Partial Damage
		- Lightly Damaged
		- Severely Damaged
	* Spillway Breach
		- Population at Risk
		- Loss of Economic Value

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Spillway Erosion Models
* USDA (Temple et al., 1994
* Modified USDA (KCD, 1995; ERDC, 2002)
* Annandale (1995)
* REMR (WES, 1998)

Unlined Spillway Erosion Risk Assessment
Phase of Erosions
Rock
Top Soil
Original Surface
Vegetal Detachment
Head-cut Development
Head-cut Advancement

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Event Tree

Sedimentary
Erosion Occurred
Head-cut Developed
Head-cut Advanced
Spillway Breach
Dam Breach

Volcanic
Spillway Flow
Intact
Local Scour
Big Pot Hole
Spillway Breach
Local Damages
Partial Damages
Dam Breach
Partial Damages

Unlined Spillway Erosion Risk Assessment
Development of Head-cut
Load: Hydrograph
Governing Equations:
Te = y(d = Ad)S
Ds/dt = kd[te tc]

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Parameters
Te = effective stress
Y = unit weight of water
D = normal depth of flow
S = surface slope
De/dt = erosion rate
Kd = detachment rate
Tc = threshold stress

Unlined Spillway Erosion Risk Assessment
Head-cut Advance
Load: Hydrograph
Governing Equations:
Dx/dt = {C(A A0) (A A0) > 0
		0 (A A0) < 0
Dx/dt = Rate of headcut advance
C = empirical parameter
A = Hydraulic attack
A0 = Threshold level

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Erosion Model  Threshold Line
Maximum qH
Erodibility Index Kh
Eroded
Threshold Line
Not Eroded

Unlined Spillway Erosion Risk Assessment
Erodibility Index Kh
Kh = Ms x Kb x Kd x J6
Ms = Material Strength Number
Kb = Block Size Number
Kd = Joint Shear Strength Number
Js = Joint Orientation Number

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Maximum Hydraulic Attack 
E = w x q x h
E= Maximum Hydraulic Attack
W = Unit weight of water
Q = Unit discharge
H = Energy line drop

Unlined Spillway Erosion Risk Assessment
Logistic Regression
* Regression for Binary Outcomes
	- Occurrence (Erosion)
	- Non-Occurrence (No Erosion)
* User of Logistic Regression Method
	- Medical
	- Business
* Probabilistic Liquefaction Analysis

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Logistic Regression
* Odds ration p/1-p
* Logit transformation
Ln[p/1-p] = b0 + blx
p = 1/1 + cxp [-(b0 + blx)]
p = probability of occurrence
b0-b1 = regression parameters
x = independent variable

Unlined Spillway Erosion Risk Assessment
Multiple Logistic Regression
P=1/1 = exp [-(b0 +b1x1 + b2x2 + .. + bnxn)]
p = probability of occurrence
b0 bv .., ba = regression parameters
xl, x2, .., xq = independent variables

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Multiple Logistic Regression for Spillway Erosion
P = 1/1 + exp [-(b0 + b1Ka + b2qH)]
Kh =  Erosion Index, Material Resistance
qH = Maximum aH, Hydraulic Attack

Unlined Spillway Erosion Risk Assessment
Result of Multiple Logistic Regression
p = 1/1 + exp [-(1.71  3.9Kh + 3.364 qH)])]
p = probability of erosion
Kh = Erosion Index, Material Resistance
aH = Maximum aH, Hydraulic Attack

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Logistic Regression for ERDC Threshold

Unlined Spillway Erosion Risk Assessment
Logistic Regression for Annandale Threshold

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Independent Variables
* Hydrograph
	- Peak unit discharges (cfs/ft)
	- Flood durations (hrs)
* Spillway Geometry
	- Lengths (ft)
	- Slopes (degrees)
* Material Index
	- Erosion Indexes

Unlined Spillway Erosion Risk Assessment
Ordinal Logistic Regression
Sj = F (Material, Peak Discharge, Duration, Average_Slope, and Length)
Data: Case Histories (USDA and COE)
Damage Levels:
No Damage 0  0.05%
Lightly Damage 0.06 - 15%
Moderately Damage 16  40%
Severely Damage 41  75%
Breach 76  100%

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Ordinal Logistic Regression
Sj = 1.515 Log_Kh + 8.635 Log_q  1.581 Log_Dura + 0.807 Slope_av + 3.975 Log_Length
Probability Formulation:
No Damage = 1/ (1 + exp (Sj-k1))
Lightly Damage = 1/ (1 + exp (Sj-k2)) - 1/ (1 + exp (Sj-k1))
Moderately Damage = 1/ (1 + exp (Sj-k3)) - 1/ (1 + exp (Sj-k2))
Severely Damage = 1/ (1 + exp (Sj-k4)) - 1/ (1 + exp (Sj-k3))
Breach = 1 - 1/ (1 + exp (Sj-k4))
K1, k2, k3, and k4 = boundary parameters from regression

Unlined Spillway Erosion Risk Assessment
Input
Unit Disch. (cfs/ft) 112.1 41.8 104.4 163.5
Duration (hours) 120 570 210 3
Erosion Index1 Kh 1/ 5340 28 103 0.01
Ave. Slope (deg) 1.4 1.32 14.04 1 7.2
Length (ft) 2200 520 230 1340 155
Probability Output
No Damage 0.001 0.990 0.000 0.029 0.000
Lightly 0.019 0.009 0.002 0.275 0.000
Moderate 0.305 0.001 0.047 0.609 0.000
Severe 0.629 0.000 0.639 0.085 0.003
Breach 00.046 0.000 0.312 0.002 0.997

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Photo of the Bluestone, WV dam
Photo of the Dalles, OR dam
The Dalles, OR Q = 2,290,000 cfs Bluestone WV Q = 430,000 cfs
Erosion Index (Kh) 1960 2734
Stream Power (Kw/mw) 125.4 22.3
Probability of Erosion 0.012 0.000

Unlined Spillway Erosion Risk Assessment
Simulation Using USDA Model
* Monte Carlo
* Latin Hyper-Cube
No Damage 0  0.05%
Lightly Damage 0.06  15%
Moderate Damage 16  40%
Severely Damage 41  75%
Breach 76% - 100%

Unlined Spillway Erosion Risk Assessment
Prioritizing Process
Ranking the outcome:
Risk = P occurrence * P failure * Consequences

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Unlined Spillway Erosion Risk Assessment
Future Research
* Erosion Index needs to be refined
* Geophysical Exploration will be useful for volcanic areas
* Effect of spillway channel geometry (curving, narrowing)
* Three dimensional erosion (side erosion)

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Appendix D
References

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Hydraulic Design of Labyrinth Weirs and Fusegates - Falvey
Labyrinth Weirs
Afshar, A., (1988). The development of labyrinth weir design. Water Power and Dam Construction, 40(5), 36-39.
Cassidy, J.J., Gardner, C.A., and Peacock, R.T., (1985). Boardman labyrinth crest spillway. American Society of Civil Engineering, Journal of Hydraulic Engineering, 111(3), 398-416.
Cassidy, J.J., Gardner, C.A., and Peacock, R.T., (1985). Closure to Boardman labyrinth crest spillway. American Society of Civil Engineering, Journal of Hydraulic Engineering, 111(6), 808-819.
Chandrasekhara, T.R., and Loganathan, V., (1985). Discussion of Boardman labyrinth crest spillway. American Society of Civil Engineering, Journal of Hydraulic Engineering, 111(6), 808-819.
Darvas, L.A., (1971). Discussion of Performance and design of labyrinth weirs, by Hay and Taylor. American Society of Civil Engineering, Journal of Hydraulic Engineering, 97(80), 1246-1251.
El-Khashab, A.M.M., and Smith, K.V.M, (1976). Experimental investigations of flow over side weirs. American Society of Civil Engineering, Journal of Hydraulic Engineering, 102(9), 1255-1268.
Falvey, H.T., (2003), Hydraulic Design of Labyrinth Weirs, ASCE Press.
Hay, N., and Taylor, G., (1970). Performance and design of labyrinth weirs. American Society of Civil Engineering, Journal of Hydraulic Engineering, 96(11), 2337-2357.
Hinchliff, D., and Houston, K.L., (1984). Hydraulic design and application of labyrinth spillways. Proceedings of 4th Annual USCOLD Lecture, January.
Indlekofer, H., and Rouv, G., (1975). Discharge over polygonal weirs. American Society of Civil Engineering, Journal of the Hydraulics Division, 101(HY3), 385-401.
Lux, F., (1984). Discharge characteristics of labyrinth weirs. Proceedings of Conference on Water for Resource Development, Coeur dAlene, ID, Aug, American Society of Civil Engineering.
Lux, F. (1985). Discussion on Boardman labyrinth crest spillway. American Society of Civil Engineering, Journal of Hydraulic Engineering, 111(6), 808-819. 
FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-4  
Lux, F., and Hinchliff, D.L., (1985). Design and construction of labyrinth spillways. 15th Congress ICOLD, Vol. IV, Q59-R15, Lausanne, Switzerland, 249-274.
Lux, F., (1989), "Design and application of labyrinth weirs," Design of Hydraulic Structures 89, Edited by Albertson, M.L., and Kia, R.A., Balkema/Rotterdam/Brookfield.
Mayer, P.G., (1980). Bartletts Ferry Project, labyrinth weir model studies. Project No. E-20-610, Georgia Institute of Technology, Atlanta, Ga., Oct. Megalhes, A.P., (1985). Labyrinth weir spillway. Transactions of the 15th Congress ICOLD, Vol. VI, Q59-R24, Lausanne, Switzerland, 395-407.
Megalhes, A.P., and Melo, J.F., (1994). Hydraulic model study of a large labyrinth weir spillway. 2nd International Conference on Hydraulic Modeling, Stratford-upon-Avon, U.K., June. Metropolitan Water, Sewerage and Drainage Board, (1980). Investigation into spillway discharge noise at Avon Dam. ANCOLD Bulletin No. 57, 31-36.
Tacail, F.G., Evans, B., and Babb, A., (1990). Case study of a labyrinth spillway.Canadian Journal of Civil Engineering, 17, 1-7.
Tullis, J.P., Nosratollah, A., and Waldron, D., (1995). Design of labyrinth spillways. American Society of Civil Engineering, Journal of Hydraulic Engineering, 121(3), 247-255.
Vermeyen, T., (1991). Hydraulic model study of Ritschard Dam spillways. Report No. R-91-08, U.S. Bureau of Reclamations, Denver, Colo.
Waldron, D.R., (1994). Design of labyrinth spillways. MSc thesis, Utah State University, Logan, Utah.
Wormleaton, P.R., and Soufiani, E, (1998). "Aeration performance of triangular planform labyrinth weirs." American Society of Civil Engineering, Journal of Environmental Engineering, 124(8), 709-719.
Wormleaton, P.R., and Tsang, C.C., (2000). "Aeration performance of rectangular planform labyrinth weirs." American Society of Civil Engineering, Journal of Environmental Engineering, 127(5), 456-465.
Yildiz, D. and Uzecek, E., (1996). "Modeling the performance of labyrinth spillways." Hydropower, 3, 71-76.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-5 

Fusegates 
Ait Alla, A., 1996, The role of Fusegates in dam safety, Hydropower and Dams, Vol. 3, Issue 6.
Bowers, P.W., Mifkovic, C.S. and Rayssiguier, 2000, Searching for conventional spillway control system alternatives, Hydropower and Dams, Issue 3, Jul.
Brink, T.G, 1996, The Effects of Waves on Fusegates, MS Thesis, Colorado State University, Fort Collins, CO.
Compte, B., Golliard, D., Boillat, J.L., Chevalier, S., and Bremen, R., 2000, Advances in spillway design using Fusegates: Application to the Montsalvens Dam, International Commission on Large Dams, 20th Congress on Large Dams, Beijing, China.
Falvey, H.T., Snell, E.F.A, and Rayssiguier, J.,1994, Increasing Shongweni Dam Discharge Capacity with a Hydroplus Fusegate System, Dam Safety Modification and Rehabilitation, 14th Annual USCOLD Lecture Series, Phoenix, AZ, June.
Falvey, H.T. and Treille, P., 1995, Hydraulics and Design of Fusegates, ASCE Journal of Hydraulic Engineering, Vol. 121, NO. 7, July.
Fauquez, J.P., 1993, Hydroplus and the Fusegate principle, International Conference, Hydropower, Energy and the Environment, Stockholm, June.
Garrec, P., 1998, Fusegates increase storage capacity at four dams in Gujarat, Hydropower and Dams, Issue 5.
Golliard, D. and Chevalier, S., 1998, An innovative solution to a safety problem on Montsalvens dam, Hydropower and Dams, Issue 2.
Gulati, O.T., 1996, Increasing the capacity of the Mahi canal at Mahi, India, Hydropower and Dams, Issue 2.
Harshbarger, E.D., 1994, Hydroplus Fusegate Evaluation, Tennessee Valley Authority, Report No. WR 28-1-900-259.
Hite, J. Jr. and Mifkovic, C., 2000, Increasing Reservoir Storage or Spillway Capacity using Fusegates, U.S. Army Corps of Engineers, Apr.
Jones, S.J., Spencer, D., Rodionov, V.B., Lounatsi, M.E. and Ait Alla, A., 1996, The reliability of fuseible gates in ice-affected environments, Hydropower and Dams, Issue, 2.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-6 

Lemprire, F. and Bessire, C., 1992, Hydroplus submersible fusegates for surface spillways, Modification of dams to accommodate major floods, Twelfth Annual USCOLD Lecture Series, Fort Worth, TX.
Lemprire, F., 1992, Overspill Fusegates, Water Power & Dam Construction, July Lemprire, F., 1995, Cost Effective improvements in fill dam safety, Hydropower and Dams, Jan.
Pittman, W.V, Watson, M.D., and Hakin, W.D., 1998, Impact of fusegate rotation on a reservoirs firm yield, Hydropower and Dams, Issue 6.
Shaw, Q.H.W., Cameron-Ellis, D.G., and Hakin, W.D., 1999, Fusegates enhance safety and increase capacity at Eikenhof, Hydropower and Dams, Issue 6, Dec.
Sikora, J., Ferns, L., Bailey, F. and Gavillet, M., 1995, MacClure dam spillway modifications with Fusegates, Proceedings of the 1995 Annual Conference of the Association of Dam Safety Officials, Sep., pp. 17-20, Atlanta, GA.
Taylor, G., Mahooty, D., and Rayssiguier, J., 2001, Historic Dam, Modern Upgrade, USSD Conference, Denver.
Trissler M. and Crawford, C., 1994, Installation of a Fusegate system at Shongweni dam, Hydropower and Dams, Nov.
Verrender, M., Mayo, N., Phillippe, M., 1994, Recent development with Hydroplus Fusegates, Australian National Committee on Large Dams, Dec., Hobart, Tasmania.
Yong, Liu, 1995, Application of Hydroplus Fusegates to flood-diversion areas of Huaihe river basin, Hydropower and Dams, Nov.
Yziquel, A., Monclar, J.M., and Chirwa, M.J., Heightening of Malawis Kamuzu II Dam Hydropower and Dams, Issue 6, Dec.

Fuse Plug Embankments - Wahl 
Tinney, E.R. and Hsu, H.Y., 1961. Mechanics of washout of an erodible fuse plug.
Journal of the Hydraulic Division, Proceedings, ASCE, Vol. 87, No. HY3, May 1961.
Pugh, C.A., 1985. Hydraulic Model Studies of Fuse Plug Embankments, U.S. Dept. of the Interior, Bureau of Reclamation, Research Report REC-ERC-85-7.
http://www.usbr.gov/pmts/hydraulics_lab/pubs/recerc/REC-ERC-85-07.pdf 
FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-7 
Crest Parapets and Dam Raising - Fuller 
Dam Safety Assurance Model Study of Tygart Dam, Tygart River, Grafton, West Virginia, Turner, Herman O., TR CHL-99-7, April 1999.
Bluestone Lake Dam, West Virginia, Rating Curve and Overtopping Study, Fuller, Billy D., ERDC/CHL TR-02-2, March 2002.
Gated Spillways Both Traditional and Rubber - Cohen 
Manuals Design of Arch Dams, 1977 
Design of Gravity Dams, 1976 
Design of Small Canal Structures, 1978 
Design of Small Dams, 1987 
Guide to Concrete Repair, 1999 
SEED (Safety Evaluation of Existing Dams), Revised Reprint 1983 

Design Standards 
Design Standards No. 3 (Revised), Water Conveyance Systems 
	Chap. 4, Tunnels, Shafts, and Caverns, 1994 
	Chap. 11, General Hydraulic Considerations, 1994 
	Chap. 12, General Structural Considerations, 1994 

Engineering Monographs 
No. 7, Friction Factors for Large Conduits Flowing Full, 1977 
No. 9, Discharge Coefficients for Irregular Overfall Spillways, 1952 
No. 25, Hydraulic Design of Stilling Basins and Energy Dissipators, Revised 1978 

Research Report No. 4, Hydraulic Downpull Forces on Large Gates, 1966 

Research Reports 
REC-ERC Research Reports 
REC-ERC-78-8, Low Froude Number Stilling Basin Design, 1978 
REC-ERC-85-7, Hydraulic Model Studies of Fuse Plug Embankments, 1985 
REC-ERC-87-6, Hydraulic Model Studies of Upper Stillwater Dam Stepped Spillway and Outlet Works, 1987 
REC-ERC-88-1, Emergency Spillways Using Geomembranes, 1988 
REC-ERC-88-2, Hydraulic Model Study of Twin Buttes Dam Fuse Plug Spillway, 1988 REC-ERC-88-3, Overtopping Flow on Low Embankment Dam-Summary Report of Model Tests, 1988 
R-03-02, A Survey of Selective Withdrawal Systems, 2003 

ACER Technical Memoranda 
Freeboard Criteria and Guidelines for Computing Freeboard Allowances for Storage Dams, ACER Technical Memorandum No. 2, 1992 

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-8 

Criteria and Guidelines for Evacuating Storage Reservoirs and Sizing Low-Level Outlet Works, ACER Technical Memorandum No. 3, 1990 
Criteria for Bulkheading Outlet Works Intakes for Storage Dams, ACER Technical Memorandum No. 4, 1982 
Guidelines for Determining Whether Normally Inundated Outlet-Works Features Should Be Examined, ACER Technical Memorandum No. 6, 1985 
Guidelines for Designing and Constructing Roller-Compacted Concrete Dams, ACER Technical Memorandum No. 8, 1987 
Guidelines for Controlling Seepage Along Conduits through Embankments, ACER Technical Memorandum No. 9, 1987 
Guidelines for Using Fuse Plug Embankments in Auxiliary Spillways, ACER Technical Memorandum No. 10, 1987 

Earthen Spillways Design and Analysis  State of the Practice - Temple Annandale, G. W. (1995). Erodibility. Journal of Hydraulic Research, IAHR, Vol. 33, No. 4, 471-494.
Barton, N. 1988. Rock Mass Classification and Tunnel Reinforcement Selection Using the Q-System. Rock Classification Systems for Engineering Purposes. Kirkaldie, L., ed., ASTM STP 984, American Society for Testing and Materials, Philadelphia, 59-88.
Bollaert, E., Falvey, H.T., Schleiss, A. (2002). Turbulent jet impingement in plunge pools: the particular characteristics of a near-prototype physical model study. Proceedings of Riverflow 2002, Louvain-la-Neuve, Belgium, 395-403.
Cato, K.D. 1991. Performance of Geological Material Under Hydraulic Stress, Ph.D. diss., Texas A&M University, College Station, Texas.
Hanson, G.J., 1991, Development of a Jet Index to Characterize Erosion Resistance of Soils in Earthen Spillways, Trans. ASAE, Vol. 34, No. 5: 2015-2020.
Kirsten, H.A.D. 1988. Case Histories of Groundmass Characterization for Excavatability. Kirkaldie, L., ed., Rock Classification Systems for Engineering Purposes.
ASTM STP 984, American Society Society for Testing and Materials, Philadelphia, PA, pp. 102-120.
Mathewson, C., Cato, K.D., and May, J. 1998. Geotechnical Aspects of Rock Erosion in Emergency Spillway Channels. Supplemental Information on Prediction, Control, and Repair of Erosion in Emergency Spillway Channels, USACE-WE, Vicksburg, MS.
Moore, J.S., Temple, D.M., and Kirsten, H.A.D. 1994. Headcut Advance Threshold in Earth Spillways. Bulletin of the Association of Engineering Geologists, Vol. XXXI, No. 2, pp. 277-280.
Perlea, V.G., Mathews, D.L., and Walberg, F.C. 1997. Rock Erosion of Unlined Spillway Chute. Nineteenth Congress on Large Dams (ICOLD), Florence, Italy.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-9 

Temple, D.M., and Hanson, G.J. 1994. Headcut Development in Vegetated Earth Spillways, Applied Engineering in Agriculture, Vol 10, No 5: 677-682.
Temple, D.M., and Moore, J.S. 1997. Headcut Advance Prediction for Earth Spillways. Trans. ASAE, Vol. 40, No. 3: 557-562.
US Army Corps of Engineers. 1990. Hydraulic Design of Spillways, Engineer Manual EM 1110-2-1603, Washington, DC.
US Army Corps of Engineers. 1994. Hydraulic Design of Flood Control Channels, Engineer Manual EM-1110-2-1601, Washington, DC.
US Department of Agriculture, SCS. 1973. A guide for design and layout of earth emergency spillways as part of emergency spillway systems for earth dams. Technical Release No. 52.
US Department of Agriculture, NRCS. 1997. National Engineering Handbook, Part 628 Dams, Chapter 51, Earth Spillway Erosion Model. Washington, D.C.
US Department of Agriculture NRCS. 2001. National Engineering Handbook, Part 628 Dams, Chapter 52, Field Procedure Guide for the Headcut Erodibility Index. Washington, D.C.
Wibowo, J. L. And Murphy, 2002. Unlined Spillway Erosion Prediction Model WES Technical Report.

Spillway Foundation Erosion - Ruff 
Jet Scour 
Annandale, G.W., (1995), Erodibility. Journal of Hydraulic Research, Vol. 33, No. 4, pp. 471-494.
Bollaert, Eric, (2002), Transient water pressures in joints and formation of rock scour due to high-velocity jet impact, Thesis, Swiss Federal Institute of Technology, Lausanne, Switzerland.
Annandale, G.W., Wittler, R.J., Scott, G., (2000), Scour Downstream of Dams Proceedings of the GeoEng 2000 Conference, Melbourne, Australia. Ed. Jean Louis Briaud. November.
Bohrer, J., Abt, S.R., Wittler, R.J., (1998), Predicting Plunge Pool Velocity Decay of a Free falling, Rectangular Jet. Journal of Hydraulic Engineering, American Society of Civil Engineers. October 1998, vol. 124, issue 10. pp 1043-1048.
Harza Engineering Company, (1993), Plunge pool performance  Project data review/Literature search, Theodore Roosevelt Dam, Lower Colorado Region, Salt River Project, Arizona, Report prepared for U.S. Bureau of Reclamation, Denver Colorado.
Hoffman, G., (1998), Jet scouring equilibrium phase. Journal of Hydraulic Engineering, American Society of Civil Engineers. October, vol. 124, issue 10. pp 430- 437.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-10 

Kuroiwa, J.M, Ruff, J.F., Wittler, R.J., Annandale, G.W., (1998), Prototype Scour Experiments in Simulated Fractured Rock and Granular Media. Proceedings of 1998 ASCE International Water Resources Engineering Conference, Memphis, TN, August.
Kuroiwa, J.M, (1999), Scour caused by rectangular jets in cohesionless beds, Dissertation, Colorado State University, Fort Collins, Colorado.
Mason, P.J., Arumugam, K., (1985), Free Jet Scour Below Dams and Flip Buckets. Journal of Hydraulic Engineering, vol. 111, No. 2, A.S.C.E., February.
Wittler, R.J., Annandale, G.W., Abt, S.R., Ruff, J.F., (1998), New Technology for Estimating Plunge Pool or Spillway Scour. Proceedings of Association of State Dam Safety Officials, Dam Safety 98. Las Vegas, NV. October 11-15.

Riprap and Concrete Wedge Blocks 
Gaston, M. L., (1995), Air entrainment and energy dissipation on s stepped block spillway, Thesis, Colorado State University, Fort Collins, Colorado.
Mishra, S. K., (1998), Riprap design for overtopped embankments, Dissertation, Colorado State University, Fort Collins, Colorado.
Slovensky, G. G., (1993), Near-prototype testing of wedge-block overtopping protection, Thesis, Colorado State University, Fort Collins, Colorado.
Wittler, R. J., (1994), Mechanics of riprap in overtopping flow, Dissertation, Colorado State University, Fort Collins, Colorado.

Dam Overtopping Protection Technologies - State-of-Practice and Research Needs - Frizell 
Embankment Overlays 
Matos, Jorge, Antonio N. Pinheiro, Antonio de Carvalho Quintela, Kathleen H. Frizell. 2001, On the Role of Stepped Overlays to Increase Spillway Capacity of Embankment Dams, International Journal of Hydraulic Research, 2001 
Hydraulics of Stepped Spillways, Proc Intl. Workshop on Hydraulics of Stepped Spillways, Zrich, Switzerland, H.E. Minor & W.H. Hager (eds). Balkema: 163-170, 2000.
Oswalt, N.R., L.E. Buck, T.E. Hepler, and H.E. Jackson, Alternatives for Overtopping Protection of Dams, ASCE Hydraulics Division Task Committee on Alternatives for Overtopping Protection for Dams, New York.
Frizell, K.H., B.W. Mefford, R. A. Dodge, T. B. Vermeyen, Embankment Dams: Methods of Protection During Overtopping, Hydro Review, Vol. X, No. 2, April 1991.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-11 

Schweiger, Paul. G., The State-of-the-Art of Armoring Embankment Dams Using Articulating Concrete Blocks, Proceedings ASDSO.
Baker, R. 2000a. The CIRIA guide for the design of stepped-block spillways. Proc Intl.
Workshop on Hydraulics of Stepped Spillways, Zrich, Switzerland, H.E. Minor & W.H.
Hager (eds). Balkema: 155-161.
Frizell, K.H., Matos, J. & Pinheiro, A.N. 2000. Design of concrete stepped overlay protection for embankment dams. Proc Intl. Workshop on Hydraulics of Stepped Spillways, Zrich, Switzerland, H.E. Minor & W.H. Hager (eds). Balkema: 179-186.
Frizell, K.H., Smith, D.H. & Ruff, J.F. 1994. Stepped overlays proven for use in protecting overtopped embankment dams. Proc. of the Association of State Dam Safety Officials, 11th Annual Conference, USA.

Riprap 
Frizell, K.H., J.F. Ruff, and S. Mishra, "Simplified Design Guidelines for Riprap Subjected to Overtopping Flow, Proceedings of the Annual Association of State Dam Safety Officials (ASDSO) Conference, Las Vegas, NV, October 1998.
Mishra, S. K., (1998), Riprap design for overtopped embankments, Dissertation, Colorado State University, Fort Collins, Colorado.
Timblin, Jr. L.O., P.G. Grey, B.C. Muller, and W.R. Morrison, Emergency Spillways Using Geomembranes, REC-ERC-88-1, US Department of Interior, Bureau of Reclamation, Denver CO, April 1988.

Gabions 
Oswalt, N.R., L.E. Buck, T.E. Hepler, and H.E. Jackson, Alternatives for Overtopping Protection of Dams, ASCE Hydraulics Division Task Committee on Alternatives for Overtopping Protection for Dams, New York.

RCC Overtopping Protection for Increasing Spillway Capacity - Hansen 
Hansen, K.D. and J. France, RCC  A Dam Rehab Solution Unearthed, Civil Engineering  ASCE, September 1986.
Hansen, K.D. RCC for Rehabilitation of Dams in the USA  An Overview, Roller Compacted Concrete III, Proceedings of the RCC Specialty Conference, San Diego, CA, ASCE, New York, February 1992, pp 22-46.
Hansen, K.D. and Bass, R.P. How Old Dams are Reborn, International Water Power & Dam Construction, June 1999.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-12 

McLean, F.G. and K.D. Hansen, Roller Compacted Concrete for Embankment Overtopping Protection, Geotechnical Practice in Dam Rehabilitation, Geotechnical Special Publication No. 35, Proceedings of the Geotechnical Engineering Division of ASCE, Raleigh, NC, April 1993, pp 188-209.

General discussion - NRCS Designs and Research Needs  James Moore 
NRCS Technical Release No. 60  Earth Dams and Reservoirs 

Spillways - An Owners Perspective - Weldon 
NONE 

General discussion  Consultants Spillway Design and Research Needs - Wade Moore 
NONE 

Vegetated Earth Spillways - Inspection, Maintenance and Monitoring - Lobrecht 
USDA  NRCS  National Engineering Manual 210-VI-NEM Part 628 Dams 
210-VI-NEH-628.50 Chapters 50 Earth Spillway Design, 
210-VI-NEH-628.51 Chapter 51 Earth Spillway Erosion Model, 
210-VI-NEH-628.52 Chapter 52 Field Procedures Guide for the Headcut Erodibility Index.
210-VI-TR-60 TR-60 Earth Dams and Reservoirs 
210-VI-NEH-728.50 SITES  Water Resource Site Analysis Computer Program 

Earth Spillways  State of Practice and Research Needs - Greg Hammer 
HEC-RAS River Analysis System  Hydraulic Reference Manual, US Army Corps of Engineers, Hydrologic Engineering Center, Davis, CA, July 1995 
Brater, Ernest F., King, Horace W., Handbook of Hydraulics, Sixth Edition, McGraw- Hill Book Company, 1976.

Issues and Research Needs Related to Hydraulics for Spillways for State Regulated Dams - Fiegle .
Fiegle, E., Issues and Research Needs Related to Hydraulics for Spillways for State Regulated Dams  State Survey Responses, Georgia Safe Dams Program, Georgia Department of Natural Resources, August 2003.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-13 

Concrete Spillway Repairs - McDonald 
Vaysburd, A.M., Emmons, P.H., McDonald, J.E., Poston, R.W., and Kesner, K.E., Performance Criteria for Concrete Repair Materials, Summary Report, Technical Report REMR-CS-62, 72 pp, US Army Engineer Waterways Experiment Station, Vicksburg, MS, March, 1999.
McDonald, J.E., Vaysburd, A.M., and Poston, R.W., Performance Criteria for Dimensionally Compatible Repair Materials, HPM&S Information Bulletin, Vol 00-1, 13 pp, Engineer Research and Development Center, Vicksburg, MS, January 2000.

Inspection of Concrete Spillways  Gated and Uncontrolled - Bill Bouley 
NONE 

Geophysics for Spillway and Seepage Evaluation - Dunscomb 
Corwin, R.W., and Butler, D.K., 1989, Geotechnical Applications of the Self-Potential Methods; Report 3: Development of Self-Potential Interpretation Techniques for Seepage Detection, Technical Report REMR-GT-6, Department of the Army, US Army Corps of Engineers, Washington, DC.
Dunscomb, Mark H. and Rehwoldt, Eric, 1999, Two-Dimensional Resistivity Profiling; Geophysical Weapon of Choice in Karst Terrain for Engineering Applications, Proceedings from the 7th Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst, Harrisburg, PA 
Dunscomb, Mark H., Rehwoldt, Eric, Matheson, Gordon M., 1999, The New View: Two- Dimensional Resistivity, 1999 Mid-Atlantic ASDSO Regional Conference, Matamoras, Pennsylvania.
Environmental & Engineering Geophysical Society, http://www.eegs.org/ 
Loke, M.H., 2001, Electrical Imaging Surveys for Environmental and Engineering Studies - A Practical Guide to 2D and 3D Electrical Imaging Surveys, Minden Heights, Malaysia, Distributed by http://www.geoelectrical.com 
Reynolds, J.M., 1997, An Introduction to Applied and Environmental Geophysics, John Wiley and Sons, New York.
US Army Corps of Engineers, 1995, Geophysical Exploration for Engineering and Environmental Investigations, CECW-EG, EM 1110-1-1802, Washington, DC, for download at http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-1- 1802/entire.pdf 
Ward, S.H., ed., 1990, Geotechnical and Environmental Geophysics, Vol. 1, Society of Exploration Geophysicists, Tulsa, OK.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways D-14 

Inspection, Maintenance and Monitoring of Service and Emergency Spillways - Johnson 
NONE 

Unlined Spillway Erosion Risk Assessment - Koester 
Annandale, G. W. 1995. "Erodibility." Journal of Hydraulic Research, IAHR, Vol. 33, No. 4, pp. 471-494.
Moore, J. S., Temple, D. M., and Kirsten, H. A. D. 1994. "Headcut Advance Threshold in Earth Spillways." Bulletin of the Association of Engineering Geologists, Vol. XXXI, No. 2, pp. 277-280.
Wibowo, J. L., and Murphy, W. L., 2004. "Unlined Spillway Erosion Prediction Model." WES Technical Report. in publication.
Mathewson, C., Cato, K. D., and May, J. 1998. "Geotechnical Aspect of Rock Erosion in Emergency Spillway Channels." Suplemental Information on Prediction, Control, and Repair o Erosion in Emergency Spillway Channels, USACE-WE, Vicksburg, MS.

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways E-1 

Appendix E 
Individual Topic Voting Results 
This appendix is a compilation of each topic difficulty and benefit result shown graphically. Each topic is shown side by side with benefit on the left and difficulty on the right of the figure box. The ratings were 1=not very beneficial, 10= very beneficial; 1=low difficulty or easy to accomplish, 10=high difficulty or very hard to accomplish. The numbers of votes received for each level of benefit or difficulty are shown across the bottom of each graph The bars show the results of voting graphically in terms of percent votes for each level divided by the total number of votes received. The mean is also shown for the category giving the voting distribution.

Topic A
Benefit
Mean: 4.8 Total: 24 Slide: 1

Topic A
Difficulty
Mean: 5.8 Total: 26 Slide: 2

Topic B
Benefit
Mean: 3.6 Total: 23
Slide: 3

Topic B
Difficulty
Mean: 5.5 Total: 22 Slide: 4

Topic C
Benefit
Mean: 5.2 Total: 25 Slide: 5

Topic C
Difficulty
Mean: 4.3 Total: 24 Slide: 6

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic D
Benefit
Mean: 5.5 Total: 25 Slide: 7

Topic D
Difficulty
Mean: 4.1 Total: 25 Slide: 8

Topic E
Benefit
Mean: 5.2 Total: 25 Slide: 9

Topic E
Difficulty
Mean: 2.9 Total: 26 Slide: 10

Topic F
Benefit
Mean: 6.1 Total: 24 Slide: 11

Topic F
Difficulty
Mean: 7.9 Total: 24 Slide: 12

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic G
Benefit
Mean: 6.0 Total: 25 Slide: 13

Topic G
Difficulty
Mean: 5.8 Total: 25 Slide: 14

Topic H
Benefit
Mean: 8.3 Total: 26 Slide: 15

Topic H
Difficulty
Mean: 6.4 Total: 26 Slide: 16

Topic I
Benefit
Mean: 8.4 Total: 25 Slide: 17

Topic I
Difficulty
Mean: 6.8 Total: 25 Slide: 18

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic J
Benefit
Mean: 2.2 Total: 23 Slide: 19

Topic J
Difficulty
Mean: 7.1 Total: 23 Slide: 20

Topic K
Benefit
Mean: 4.0 Total: 24 Slide: 21

Topic K
Difficulty
Mean: 4.6 Total: 23 Slide: 22

Topic L
Benefit
Mean: 8.6 Total: 27 Slide: 23

Topic L
Difficulty
Mean: 7.8 Total: 26 Slide: 24

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic M
Benefit
Mean: 7.4 Total: 27 Slide: 25

Topic M
Difficulty
Mean: 4.5 Total: 26 Slide: 26
Topic N
Benefit
Mean: 6.8 Total: 25 Slide: 27

Topic N
Difficulty
Mean: 4.0 Total: 24 Slide: 28

Topic O
Benefit
Mean: 3.2 Total: 24 Slide: 29

Topic O
Difficulty
Mean: 4.6 Total: 23 Slide: 30

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic P
Benefit
Mean: 3.3 Total: 22 Slide: 31

Topic P
Difficulty
Mean: 6.1 Total: 23 Slide: 32

Topic Q
Benefit
Mean: 4.4 Total: 24 Slide: 33

Topic Q
Difficulty
Mean: 6.8 Total: 25 Slide: 34

Topic R
Benefit
Mean: 7.8 Total: 25 Slide: 35

Topic R
Difficulty
Mean: 6.8 Total: 25 Slide: 36

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic S
Benefit
Mean: 5.4 Total: 22 Slide: 37

Topic S
Difficulty
Mean: 5.8 Total: 22 Slide: 38

Topic T
Benefit
Mean: 5.6 Total: 25 Slide: 39

Topic T
Difficulty
Mean: 6.2 Total: 25 Slide: 40

Topic U
Benefit
Mean: 5.6 Total: 23 Slide: 41

Topic U
Difficulty
Mean: 6.3 Total: 23 Slide: 42

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic V
Benefit
Mean: 5.1 Total: 23 Slide: 43

Topic V
Difficulty
Mean: 4.9 Total: 24 Slide: 44

Topic W
Benefit
Mean: 4.8 Total: 22 Slide: 45

Topic W
Difficulty
Mean: 4.5 Total: 23 Slide: 46

Topic X
Benefit
Mean: 5.7 Total: 20 Slide: 47

Topic X
Difficulty
Mean: 5.0 Total: 22 Slide: 48

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic Y
Benefit
Mean: 4.4 Total: 25 Slide: 49

Topic Y
Difficulty
Mean: 6.3 Total: 25 Slide: 50

Topic Z
Benefit
Mean: 8.1 Total: 24 Slide: 51

Topic Z
Difficulty
Mean: 7.4 Total: 24 Slide: 52

Topic AA
Benefit
Mean: 3.8 Total: 25 Slide: 53

Topic AA
Difficulty
Mean: 5.7 Total: 25 Slide: 54

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic AB
Benefit
Mean: 5.5 Total: 25 Slide: 55

Topic AB
Difficulty
Mean: 6.4 Total: 24 Slide: 56

Topic AC
Benefit
Mean: 6.5 Total: 24 Slide: 57

Topic AC
Difficulty
Mean: 5.8 Total: 25 Slide: 58

Topic AD
Benefit
Mean: 4.8 Total: 24 Slide: 59

Topic AD
Difficulty
Mean: 4.7 Total: 24 Slide: 60

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways

Topic AE
Benefit
Mean: 5.3 Total: 24 Slide: 61

Topic AE
Difficulty
Mean: 4.7 Total: 23 Slide: 62

Topic AF
Benefit
Mean: 6.1 Total: 23 Slide: 63

Topic AF
Difficulty
Mean: 3.8 Total: 24 Slide: 64

Topic AG
Benefit
Mean: 5.3 Total: 24 Slide: 65

Topic AG
Difficulty
Mean: 6.0 Total: 23 Slide: 66

FEMA Workshop - Issues, Remedies and Research Needs Relating to Service and/or Emergency Spillways