| Abstract/Description or Keywords |
The Interior Watershed Assessment Procedure (IWAP) is designed as a tool to aid in understanding the type and extent of potential hydrologic problems in a watershed. Using this information, forest managers can determine the effects, from a hydrological standpoint, that past forestry practices may have had on the watershed and how future activity may impact sensitive sub-basins. This assessment focuses on four main parameters: changes to peak flow, potential debris slides, the capacity for accelerated surface erosion, and impacts to the channel riparian buffer. There are three levels of assessment in the IWAP procedure as described in the Forest Practices Code IWAP Guidebook (1995): Level 1: A reconnaissance level assessment intended as a coarse filter to identify watersheds that may have impacts from the cumulative effects of past forest harvesting or planned future forest harvesting. Level 2: An overview stream channel assessment performed by individuals with basic experience in hydrology and/or geomorphology (see Channel Assessment Procedure Guidebook). Level 3: A detailed assessment is performed by a watershed specialist, involving field work. This work is guided by the results of the Level 1 and Level 2 Assessment. The Level 1 Assessment does not determine whether impacts to the watershed have occurred. Rather, it is useful in identifying those sub-basins which may have sustained impacts due to past timber harvesting or other forestry related activities. For areas which have planned future harvesting, a second Level 1 may determine if the sub-basin is susceptible to impact. It should be noted that the Level 1 IWAP procedure has certain limitations which confine the scope of its recommendations. Depending on the source or accuracy of information used, the results of the analysis may not be a precise reflection of present conditions. For this reason, recommendations are directed at whether or not to proceed with further levels of assessment. |
