Identifying Uncertainties

It is important to understand the level of uncertainty associated with impact determinations. Decision makers often consider uncertainty when deciding among alternatives. Monitoring programs typically address areas of uncertainties.

As discussed in Determining the Magnitude of Impacts, impact determinations are often based on a number of assumptions. Each of the assumptions has some uncertainty associated with it. To compensate for uncertainties, conservative assumptions are usually made to ensure that impacts are not underestimated.

Even with conservative assumptions, impacts that are poorly understood (e.g., the response of resources to the environmental changes brought about by the project is not known) can be underestimated or improperly characterized. Conservative assumptions can result in greatly overestimating impacts and unnecessary costs for a project if mitigations are not properly directed and scaled to the impact.

For impacts that are quantified using a model, the analyst typically has a good sense of where the uncertainties lie. Often, sensitivity analyses can be performed with models to identify which variables contribute the most uncertainty to the results.

Identifying uncertainties associated with less quantitative assessment methods will rely heavily on the professional judgment of the analyst. A determination will have to be based on the current understanding of the resource and its response to environmental change. This may be based largely on existing literature, studies, or measured resource responses in other geographic areas.

Monitoring programs are usually developed to determine or verify the impacts to various resources. An important component of any monitoring program will specifically address uncertainties. Resolving uncertainties will be important for future related projects, fine-tuning of operations, and refinement of a mitigation strategy.