|
Decision analysis techniques may be used as an important guide in selecting an urban runoff control program. Decision analysis is a systematic procedure that enables one to study the trade-offs among multiple and usually conflicting program objectives. An alternative procedure is to separately determine the programs necessary to meet each objective and to use the least costly program that satisfies all the identified critical objectives. This is an acceptable procedure some of the time, but it may not result in the most cost-effective program, especially when multiple objectives need to be considered. Decision analysis considers the partial fulfillment of all the objectives. It translates these into their relative worth to the decision-maker and other interested parties. This paper describes the output information calculated by WinSLAMM, the Source Loading and Management Model, and how it can be used in decision analysis procedures of varying complexities.
The decision analysis approach outlined in this paper has the flexibility of allowing for variable levels of analytical depth, depending on the problem requirements. The preliminary level of defining the problem explicitly in terms of attributes often serves to make the most preferred alternatives clear. The next level of analysis might consist of a first-cut assessment and ranking as described in the example given in the paper. Several different utility function curve types are assumed and an additive model is employed. Spreadsheet calculations with such a model are easily performed, making it possible to conduct several decision analysis evaluations using different trade-offs, representing different viewpoints. It is possible there will be a small set of options that everyone agrees are the best choices. Also, this procedure documents the process for later discussion and review. Sensitivity analyses can also be conducted to identify the most significant factors that affect the decisions. The deepest level of analysis can utilize all the analytical information one collects, such as probabilistic forecasts for each of the alternatives and the preferences of experts over the range of individual attributes. Monte Carlo options available in WinSLAMM can also be used that consider the uncertainties in the calculated attributes for each option. Decision analysis has several important advantages. It is very explicit in specifying trade-offs, objectives, alternatives, and sensitivity of changes to the results. It is theoretically sound in its treatment of trade-offs and uncertainty. Other methods often ignore uncertainty and rank attributes in importance without regard to their ranges in the problem. Decision analyses can also be implemented flexibly with varying degrees of analytical depth, depending on the requirements of the problem.
|
