Managing Risk to Support the Core Mission

Dam Safety Program
Reclamation manages 476 dams and 

dikes in the Western 17 United States

370 are High or Significant Hazard

106 are Low Hazard
Bureau of Reclamation

Original Construction Dates

0 20 40 60 80 100 1900's

1910's

1920's

1930's

1940's

1950's

1960's

1980's to Present

1970's

Embankment Concrete Composite

More than 

50 years old
Teton Dam Failure – 1976

11 killed, 1⁄2 billion dollars property damage

• Prompted new 

federal 

legislation on 

dam safety

• Reclamation’s 

dam safety 

program 

established 

soon after
• National Dam Inspection Act (1972)

(COE)

• Reclamation Safety of Dams Act (1978) 

Amended (1984, 2000, 2002, 2004)

• National Dam Safety Program Act (2002)

(FEMA)

• Dam Safety and Security Act (2002)

(FEMA)

Dam Safety Related Legislation
Reclamation Safety of Dams Act

“In order to preserve the structural safety of 

Bureau of Reclamation dams and related 

facilities, the Secretary of the Interior is 

authorized to perform such modifications 

as he determines to be reasonably 

required.”
• Authorizes modification of Reclamation dams “the cause 

of which results from new hydrologic or seismic data or 

changes in the state of the art criteria...deemed 

necessary for safety purposes”

• Does not address conditions “resulting from age and 

normal deterioration or from nonperformance of 

reasonable maintenance” 

• 75 dams repaired to date under Safety of Dams Act

 The Act:
Dam Safety Program 

Processes

• Safety Evaluation of Existing Structures 

(SEED) Process

 Non-reimbursable

 Risk identification and evaluation phase

• Initiate SOD Corrective Action 

 (ISCA) Process 

 Reimbursable

 Risk reduction phase
What is Risk?

Reclamation Dam Safety Definitions

Annualized failure probability

• P (failure) = P (load) x P (response to the load)

Annualized loss of life (risk)

• Risk = P (load) x P (response) x Consequences
What is Risk Analysis?

The procedure to identify and quantify risk by 

establishing potential failure modes, providing numerical 

estimates of the likelihood of an event in a specified 

time period, and estimating the magnitude of the 

consequences.

The use of risk estimation (analysis) in decision-making

What is Risk Assessment?
Risk Analysis Process

• Determine Failure Modes

• Construct event tree

• Discuss nodes

• List what’s known/unknown

• Estimate probability

• Examine conclusions
Estimate Load Probabilities and 

Consequences

• Estimates made by specialists in most situations

• Seismic hazards estimated by seismologists (input from 

geologists)

• Hydrologic hazards estimated by flood hydrologists 

(input from meteorologists and geologists)

• Consequences estimated by specialists with inundation 

and dam failure expertise
Estimate Response Probabilities

• Usually a very difficult part of the process

• Estimates made by those most familiar with the behavior 

of the dam

• Break down the overall dam responses into smaller 

steps that are easier to understand and estimate

• “Toolboxes” have been and continue to be developed

• See Reclamation and USACE Best Practices in Dam 

Safety Risk Analysis trainings

http://www.usbr.gov/ssle/damsafety/Risk/methodology.html
Event Tree Construction
1.E-08

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1 10 100 1000 10000

f, Annualized Failure Probability (AFP) 

N, Estimated Life Loss

Noname Dam

Total Risk and 

uncertainty 

bounds

Static Failure 

Mode 

Hydro Failure 

Mode 

Seismic Failure 

Mode 

Notes:
Guidelines for Achieving 

Public Protection in 

Dam Safety Decision Making

• Guidelines ensure consistent and 

adequate levels of public protection 

when evaluating and modifying 

existing dams and designing new 

structures

• Define how to incorporate risk-based 

evaluations into the dam safety 

decision making process

Guidelines consider:

• Annual Probability of dam failure or 

condition that results in an 

unintentional release of reservoir

• Expected Loss of Life
Reclamation (2011)

Public Protection Guidelines

Rationale

Examples of Use
Issue Evaluation

• More detailed studies of the loadings

• Field Exploration

• Analyses

• Team Risk Analysis

• Recommendations

– Risks below guidelines

– Proceed with corrective action

• Decision Document
No-Name 

Dam
Dam Safety Program 

Processes

• Safety Evaluation of Existing Structures 

(SEED) Process

 Non-reimbursable

 Risk identification and evaluation phase

• Initiate SOD Corrective Action 

 (ISCA) Process 

 Reimbursable

 Risk reduction phase
Examples of Risk Reduction Actions

• Short-term actions

– Investigation of uncertainties

– Reservoir restrictions

– Increased monitoring

– Operational changes

– Interim Repairs

– Upgraded EAP

A.V. Watkins Dam Emergency Repair

Upstream Berm

Deer Flat Dam Interim Repair

Upstream Berm
Examples of Risk Reduction Actions

• Long-term actions

– Load definition

– Data collection

– Structural modification

– Long-term reservoir restriction

Deer Flat Dam Outlet Works Replacement
• Limited resources

Where can the funds be most efficiently expended to 

protect the population downstream of our 

facilities?

• Understanding of Uncertainty

How much do we really know about a structure? 

Will it affect our understanding about its health?

Why Risk Based Decisions?
• Risk estimates focused on identified failure modes 

are easier to understand for decision makers, 

management, our customers and the public.

• Risk is now the primary justification for prioritizing 

and pursuing work activities. 

• Risk is a convincing tool to explain why the dam 

safety program takes actions and how funds are 

being expended. 

Why Risk Based Decisions?
Benefits of Risk Based Decisions

• Complies with Federal Guidelines for Dam Safety 

• More comprehensive and consistent evaluations - less 

subjectivity

• Better focus on process of data collection

• Improved consistency in decisions

• Better focus in recommendations

• Better definition of objectives in scoping out work 

products

• Resource prioritization

• Project Justification
Questions?

Reclamation’s Dam Safety Program

• Public Protection Guidelines

• Rationale

• Examples of Use

Revised 2011

http://www.usbr.gov/ssle/damsafety/references.html