The Approach to Appraisal • Describing the impacts • Using ASTs • Identifying the impacts • Valuing the impacts • Obtaining a new value

Describing the impacts

The first step in any project appraisal is to identify the impacts that are expected to occur against a pre-determined baseline. The baseline required is likely to differ according to the decision that is required.

In many management decisions, the current situation will form the most appropriate baseline, as the aim of management decisions would be to change the current situation. Thus, project appraisal of the expected conditions after the action has been taken can be compared to the current conditions. An AST can be used to keep a record of the assumptions made in estimating what the impacts of management decisions may be and can then be used to monitor whether the expected changes actually occur, once the action has been carried out. Such monitoring will provide useful information on how actions affect saltmarshes and could then be used to improve the future management of a site.

In flood defence, the baseline is taken as the do-nothing (or walk away) option. This is a zero cost option that literally involves no action on the site. The impacts (positive and negative) of undertaking various actions are then compared against this baseline. Such an appraisal will need to be undertaken if management is required for flood defence purposes (e.g. managed realignment).

For compensatory habitat, the aim usually is to identify the least-cost method of providing the benefits required. Here, the baseline may also need to relate to a do-nothing baseline. In many cases, this may be very similar to the current situation.