GEOL 5903 Seminar: Chelsea Renaud
25 November 2019
GEOL 5903 Seminar: Chelsea Renaud
Title: "Large Woody Debris: Habitat restorer or engineering disaster?"
Location & Time: Huggins Science Hall, Room 336, 12:30 p.m.
Abstract:
River channels are commonly altered to accommodate human occupation of river corridors. River restoration is a relatively recent practice aimed at restoring degraded habitat primarily through the introduction of in-stream structures and large woody debris (LWD). Despite a large body of literature that describes the utility of LWD in natural streams, the addition and/or removal of LWD as a restoration strategy is highly controversial. Studies primarily from ecology-focused research argue that the addition of LWD to streams during restoration increases in-stream cover, enhances salmonid populations, decreases stream velocity, and increases pool frequency. Negative impacts such as decreasing insect diversity and enhanced sedimentation are acknowledged but considered relatively minor. Engineering studies commonly support the removal of LWD to reduce flooding, ice formation and sediment deposition but also acknowledge a negative impact on a variety of species. Management decisions are often based on an anthropocentric risk assessment of the watershed. The decision to either introduce or remove LWD is often not based on site-specific criteria, but on prior studies that did not incorporate an integrated geomorphological, ecological and geotechnical perspective. The controversy surrounding the use of LWD in stream restoration depends on the scientists perspective with engineers focused on stream flow and stability, while ecologists focus on habitat productivity. In order for stream restoration to be successful, an integrated geomorphological approach is required to provide practical recommendations and long-term management plans to combine habitat productivity with stream stabilization.