Living with Dams

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Living with Dams: Extreme Rainfall Events | 2015 | 19
4. Extreme Incident Planning
including Emergency Action
Procedures
Dams do fail! Often these failures
will cause extensive property
damage, personal injuries and
in some situations, loss of life. To
minimize the consequences of a
dam failure, it is imperative that a
dam owner prepare an Emergency
Action Plan (EAP) for their dam.
An EAP is a formal document that
identifies emergency conditions
at a dam and the areas that would
be inundated if the dam were to
fail. It specifies preplanned actions
to be followed to moderate or
alleviate problems at the dam and
to provide adequate downstream
warning of failure. In the case of
a dam failure, the EAP may help
to minimize the consequences of
the failure. EAPs are required by
most State Dam Safety Regulatory
Programs for high hazard dams.
Key components of an EAP
would include:
Inundation Maps indicating
areas that will be impacted by
the dam failure flood wave
Notification Flowcharts for
warning of inhabitants in
inundation areas by Emergency
Management Authorities
Monitoring - Emergency
Detection, Evaluation and
Responsibility Protocol
Preventative Action – Effective
response actions to prevent
failure
5. A Dam Owners Obligation -
Meeting Current Standards
Spillway Design Criteria
The spillway capacity of any dam
should, at a minimum, comply
with the current state guidelines
for the dam’s spillway design
capacity. Most all of these state
guidelines relate directly to extreme
rainfall events and to hazard
potential classification of the dam.
Historically, standards for dam
spillway design floods have varied
from state to state, but typically
have been specified as a flood
resulting from some significant
percentage of an extreme rainfall
event known as the Probable
Maximum Precipitation (PMP).
Recently published national
guidelines for selecting and
accommodating inflow design
floods (IDF) for dam structures
recommends more rigorous
analyses such as an incremental
dam breach consequence analysis,
Owner and community
vigilance is critical.