GEOMORPHIC SIGNIFICANCE OF LARGE WOODY DEBRIS IN STREAMS AFFECTED BY WILDFIRE AND MOUNTAIN PINE BEETLE IN THE SOUTHERN INTERIOR, BRITISH COLUMBIA

Large Woody Debris (LWD) plays a critical role in maintaining the structure and function of aquatic ecosystems, a role which is extremely pronounced in headwater streams. LWD has been documented to create significant elevation loss in a stream reach, store sediment, increase channel and habitat complexity and force as many as 90% of the pools in headwater streams. In the interior of British Columbia, several large scale natural (fire and mountain pine beetle (MPB)) disturbances are severely impacting forest ecosystems, and concerns have been expressed regarding the impacts on aquatic ecosystems. The goal of this research is to quantify the impacts of these disturbances on the physical habitat and morphology of headwater streams in the BC interior as part of an ongoing research project into the impact of fire and MPB disturbances on LWD and aquatic ecosystems. Three disturbed sites and three corresponding control sites were established for each disturbance category. LWD characteristics for each of the sites were collected, as well as morphological characteristics including pool frequency and size, gradient, width to depth ratio and complexity, and longitudinal profile. The morphological characteristics were then compared between and within disturbance categories, and causative relationships established with LWD characteristics. The data collected will aid in designing effective management strategies for disturbed forest ecosystems.