FLOOD01647

• County: Statewide
• Title: Optimal Sizing of Urban Flood Control Systems
• Date: 3/1/1974
• Prepared For: US
• Prepared By: COE
• Floodplain - Doc Type: Educational/Technical/Reference Information

Output Results,- The information output from the application of this technique
could, if not carefully controlled by a pragmatic study procedure, engulf the
analyst. The technique provides the capability to "what if" a great number
of items that probably would not be otherwise analyzed. Tools of this kind
should of course be applied to conduct sensitivity analysis but within reason
so that only information useful in the planning study is generated. It is worth
emphasizing herein that all analysis tools, and in particular computerized
methodology, have as their primary function the generation of information that
will be of use in decision making; not removing any decision-making requirements
from the planning function. Data are not necessarily information.
The outputs of a system optimization run for a set of system components,
performance functions costs, and economic functions are: (I) The derived optimal
size of each component of the system; (2) complete hydrologic simulation for
the derived system; (3) economic expected annual damage analysis for each
damage center in the system; (4) costs for each component of the system;
and (5) a system summary of component sizes, cost, performance, and system
net benefits for the derived optimum systel1}. Ref. 4 contains detailed illustrated
examples of data coding and program output together with explanations of data
sources and output interpretation.
Resources and Costs.- The Blue Waters Ditch analysis provides some insight
into the manpower requirements and computer costs of applying this technique.
The information had been previously developed for the Blue Waters Ditch area.
The primary effort was therefore to assemble the hydrologic data of loss rates,
unit hydrographs, routing criteria, etc., economic flow damage information for
the damage centers, and cost relationships in a form acceptable to the computer
program. The specific studies were processed and information analyzed as the
results became available. There were nine damage centers within the basin;
nine storage areas, two of which were variable in size; and one pumping facility.
The data preparation for the processing required about a man-week on the
part of a hydrologist, economist, and water resources planner. The detail
processing and interaction for the studies required about another week's time
of each of these individuals. The computer time associated with processing
a run was not trivial. Efficient processing for a complex system such as Blue
Waters requires a large capacity high-speed computer. While computer execution
times are rather meaningless because they are unique to a specific computer
facility and optimizatiOll problem, the following computer resources used for
the Blue Waters studies might be of interest. To process a given system
configuration to determine the optimum size of each of three components
optimized and to output the results required 15 min of accounting unit equivalents
on a CDC 7600 computer and resulted in costs that ranged between $30 and
$50 per computer run. The actual execution time ranged between J.5 min and
2.0 min but a great amount of input-output and system storage were required.
The study results were generated by about 12-15 successful computer runs.

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SUMMARY AND CONCLUSIONS

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A technique has been developed and the capability added to an existing Corps
of Engineers computer program, HEC-J (I), that automatically determines the
sizes of urban flood-control system components that result in maximizing total