Spatial Multiple Criteria Decision Analysis Supporting Site Selection for Flood Water Spreading

The area selection process is using the value focused approach to define and identify the flood water spreading area characteristics, which is later on used for selection and evaluation of the identified potential areas. A criteria structure for design and evaluation of the area has been developed and applied. In the assessment process extensive number of indicators, derived through hydrological model, GIS and remote sensing techniques have been applied. In the evaluation process extensive use has been made of spatial multicriteria evaluation software that has been recently developed at ITC “ILWIS-SMCE”. For partial valuation of the indicators, as well as their respective priority spatial AHP has been applied. Introduction: Decision-making is a process involving a sequence of activities that starts with recognition of a decision problem and ends with recommendation for a decision. The quality of the decision depends on the sequence and quality of the activities that are carried out. Depending on the situation, there is a number of ways in which the sequence of activities can be organized. According to Keeney (1992), two major approaches can be distinguished, the alternative-focused, and the value-focused approach. The alternative-focused approach starts with development of alternative options, specification of values and criteria, then evaluation and recommendation of an option. The value-focused approach on the other hand, considers the values as the fundamental element in the decision analysis. Therefore, it first focuses on the specification of values (value structure), then considering the values, feasible options are developed and evaluated based on the predefined value and criteria structure. This implies that decision alternatives should be generated so that the values specified for a decision situation are best achieved. Naturally, in decision problems which alternative options have to be developed and then evaluated the value-focus approach can be much more effective, however if the decision problem starts with choice of option, the alternative-focused is more relevant. This kind of decision problem can be well supported by SMCDA methods, which represent a “transparent way to systematically collect and process objective information, express and communicate subjective judgments concerning choice affecting several stakeholders”. This concept has been applied in the site selection process for flood water spreading process. Most aquifers in semi-arid regions suffer from over-exploitation of groundwater. It is therefore important to augment the groundwater resource by artificial recharge, using flood water that in many cases are destructive and not effectively used. Floodwater spreading schemes if properly selected and implemented requires relatively low initial investment with higher efficacy of resources compared to the construction of dams. This has been proven in a number of countries, e.g., Iran. However, a large number of factors play a role in the selection of suitable sites for flood water spreading. These are: geology, geomorphology, soil properties, hydrological properties (runoff’, sediment yield, infiltration and groundwater conditions), the environmental and socio-economic (irrigated agriculture, flood damage mitigation, environment, employment) factors. Hence, the site selection decision is quite complex process which requires evaluation and aggregation of diverse number of indicators.