Issues in Water Resources Impact Assessment

Formal impact assessment, defined as the identification, description, and evaluation of changes associated with proposed actions, have been mandated by recent legislation relevant to federal water resources agencies. This paper uses an example involving proposed reservoirs in Carmel Valley, California, to demonstrate the various concepts which are introduced. The paper demonstrates how evaluative factors, defined as the goals, concerns, constraints, etc., that affected publics and other decision makers consider in ranking alternative actions, can be used in deciding on which impacts to forecast and at what levels of detail. The paper presents a classification of causative factors which encourages a systematic examination of the various aspects of a proposed action that may bring about change. Network diagrams of cause-effect relations, and the problems associated with the analysis of indirect impacts are also analyzed. The paper summarizes a number of characteristics of impacts which can be used in describing the results of an impact assessment.