EP 1165-2-1
30 Jul 99
13-3. Flood Related Planning Policy. It is the policy of the Corps
of Engineers to consider in the planning process all practicable and
relevant alternatives applicable to flood damage reduction. No one
alternative will be pre-judged superior to any other. Consideration
will be given both to measures intended to modify flood behavior
(structural measures) and those intended to modify damage
susceptibility by altering the ways in which people would otherwise
occupy and use flood plain lands and waters (nonstructural measures).
The fundamental goal is to develop, define and recommend a robust
solution that has public and institutional support (having
appropriately determined how well an economical plan can be made to
function, how capable are the responsible interests to operate and
maintain it, and how safe will be the people who will depend on it).
(ER 1105-2-100)
a. Structural Measures. These include dams and reservoirs,
levees, walls, diversion channels, bridge modifications, channel
alterations, pumping, and land treatment. All such measures reduce
the frequency of damaging overflows.
b. Nonstructural Measures. These include flood warning and
preparedness; temporary or permanent evacuation and relocation; land
use regulations including floodway delineation, flood plain zoning,
subdivision regulations and building codes; flood proofing; area
renewal policies; and conversion to open space.
13-4. Design Flood Criteria. The Corps policy in design of flood
damage reduction projects is to provide an optimum degree of
protection consistent with safety of life and property. The Corps
seeks an economically efficient degree of protection and land use in
agricultural areas, and acceptable reduction of risks and preservation
of environmental values in protecting other rural and urban areas.
Definitions for certain significant storms and floods, and for terms
that relate flood magnitude to project performance, have been adopted
as follows:
a. Standard Project Storm (SPS). The SPS is a hypothetical
storm having the most severe flood-producing rainfall depth-area-
duration relationship and areal distribution pattern that is
considered reasonably characteristic of the region in which the
drainage area is located. It is developed by studying the major storm
events in the region, excluding the most extreme. Development of the
SPS may involve transposition and adjustment of a large storm from its
observed location to the locality of concern (EM 1110-2-1411). When
that is the case, studies are to be coordinated through CECW-EH for
review by the Hydrometeorological Section of NWS.
b. Standard Project Flood (SPF).
The SPF is the discharge
hydrograph resulting from the SPS. SPF for projects east of the 105th
meridian may be developed using EM 1110-2-1411. For projects located
west of the 105th meridian, use 50 percent of the Probable Maximum
Flood (PMF) for SPF.
c. Probable Maximum Precipitation (PMP). Theoretically, the
PMP is the greatest depth of precipitation for a given duration that
is physically possible over a given size storm area at a particular
geographical location during a certain time of the year. Development
of the PMP considers all storms of record and the observed
precipitation is increased by maximizing the moisture inflows to the
storm system. Generalized depth-area-duration and seasonal
13-2
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