Demonstration Flow Assessment: Judgment and Visual Observation in Instream Flow Studies
Steven F. Railsback, John Kadvany · Fisheries · 2008
Abstract The Demonstration Flow Assessment (DFA) method evaluates instream flow benefits using expert judgment and direct observation of habitat during several flows. Early DFA applications were low-effort, qualitative, and vulnerable to well-known biases. We describe a higher-effort, more quantitative DFA (or expert habitat mapping) approach that uses techniques from the judgment-based decision analysis literature to increase objectivity and reproducibility. Specific metrics—habitat types to be quantified visually during flow observations—are designed from appropriate conceptual models of how flow affects target resources. During field observations, patches of each habitat type are delineated by consensus and marked on maps for digital analysis. A case study illustrates these procedures applied to instream flows for salmon spawning and rearing.