It starts with an office analysis, based on maps and air photos, that identifies the overall risk from the cumulative effects of past logging and other resource uses in the watershed. If this analysis highlights problems, the assessment can be extended to include, for example, field investigations of damaged streams. Reviewing and commenting on the recommendations arising from the watershed assessment is a major function of watershed round tables, as we discussed in Chapter 2 . A hazard evaluation focuses on problem areas. It provides information about terrain or soil conditions that may cause landslides or erosion.
Mapping locates problem areas, which field assessments then examine in detail.
All potentially unstable areas found by mapping, with limited exceptions, must receive a field assessment. So must all roads, unless mapping has shown they are not in an area of high erosion risk. Once the initial phase-in period for hazard evaluation is past, the Code will require that mapping and most field assessments be carried out by registered professionals. A hazard evaluation can lead to restrictions on logging, such as no clearcutting or no skidder trails. However, logging is only banned if landslide risk is high or erosion risk very high.