FLOOD02543

• County: Statewide
• Basin: Statewide
• Title: Emergency Action Planning Guidelines for Dams
• Date: 2/1/1985
• Prepared For: US
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

example of an inundation map for an urban area is shown in Figure 1. These
same maps may be used to show planned evacuation routes. However, the
limitations of the map should be identified.

Generally, an inundation map depicting both the breach and large flood
condition should be included in the plan. Although additional conditions
could be used, caution should be used to keep the map from becoming cluttered
and to keep the plan simple enough to be clear and understandable.
Generalized breach inundation maps may be used in the plan if sufficient for
clearly depicting the inundated areas. Generalized maps may need to be
supplemented with larger scale and more detailed maps in some areas. The
mapping and the number of different flooded areas should be coordinated with
local officials who are developing evacuation plans. It may be appropriate to
supplement the inundation maps with water surface profiles in critical areas.

For detailed maps, it is recommended that the best available maps for
evacuation planning should be used. This may be topographic or orthographic
mapping or street maps. The lines delineating the inundated area should be
drawn in such thickness or form (solid line, dashed line, dotted line) as to
identify the inundation limits as the main features of the map but not bold
enough to obliterate features which would be inundated by the flood waters..
When plotting inundation limits between cross sections used for the analysis,
the lines should reasonably reflect the change in water levels caused by
topographic patterns and man-made features.

When inundation lines enter the area of an existing lake or reservoir,
they should represent an increase in the water level of such lake or
reservoir. Should this increased water level overtop the dam, the appropriate
inundation lines should extend downstream of such dam.

For dams not in series but which affect a common downstream area, it is
usually adequate to consider the breach condition for each dam individually
unless special conditions would warrant multiple failure considerations.
Breach inundation lines of such dams then should consist of a line enveloping
the lines for the individual breaches when common areas would be inundated.

(b) Other Methods. Development of the flood plain below some dams
1S sparse and the expense of preparing inundation maps may not be warranted.
Flooding information can be readily provided by vicinity maps with pertinent
information at the key locations. Individuals living between key locations
can estimate their vulnerability by interpolating data from locations upstream
and downstream of their site. Information on depth of flooding and time of
travel for floods to reach specific locations is also provided as illustrated
in Figure 2.

E. Emergency Action Plan Outline. Chapter II provides a suggested outline
for an emergency action plan (EAP).

An emergency action plan should be tailored to the specific dam or system
of dams. The amount of detail for a specific dam may be more or less than
that shown in this outline. Thus, tpe outline is not intended to be all
inclusive, but rather to guide the user and to provide a uniform format. Dams

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