31 Mar 95
Figure 5-5. Pump station benefit-cost curve
should be developed and used to assist in determination of the
susceptibility to damage (and increase available storage) should
appropriate pumping station capacity. The economically
be evaluated. Floodproofing, raising, and relocation measures
optimal plan is the recommended plan in agricultural areas and
are generally more economically justified than structural
for most urban areas.
measures when only a few structures are involved. Similarly,
implementing nonstructural measures to a few structures to
permit increasing the size of a detention basin may be more
Evaluation of increased detention storage capacity.
attractive than increasing the size of gravity outlets or pumping
stations. Residual damages for evaluated plans would be
revised based on new stage-damage relationships resulting from
(1) It is prudent to investigate the tradeoffs between
implementing the nonstructural measures.
pumping capacity and ponding area storage. Pumps are
expensive and an increase in storage capacity will typically
(4) Other social, institutional, and environmental issues,
allow reduction in required pumping capacity. Several
including the management of future development, and flood
measures can be evaluated, including increasing the physical
warning and preparedness programs, would also be evaluated
size of the ponding area and nonstructural actions that will
in the final plan selection.
reduce the damage for a given ponding stage.
(2) The sensitivity of ponding area size versus pumping
Comparison of Plans
capacity can be readily determined using HEC-IFH. The plan
with the identified economically optimal gravity outlet and
One important aspect of HEC-IFH is the ability to generate
pumping station would be the base plan for determining if
results from different plans and to compare them directly. The
excavation is feasible.
effects of different conditions or assumptions can be quickly
evaluated. Up to seven different plans may be selected for
(3) Temporary evacuation, raising existing structures,
comparison using HEC-IFH. Each plan is produced by
permanent relocation of structures and/or occupants,
performing the interior analysis using various combinations of
floodproofing, and other nonstructural measures that reduce