Efficacy of restoration using instream woody debris in disturbed coastal plains streams: Influence of hydrology and geomorphology

Submerged large woody debris is a critical habitat feature in sandy coastal plains streams; thus, in disturbed catchments, reduction of instream wood from entrainment or burial by sediment can negatively affect benthic communities. In 2003 we created a series of artificial woody debris dams (sectioned logs from felled riparian trees) to enhance benthic communities in 4 disturbed streams at Fort Benning, GA. Effectiveness of debris dam additions on biotic recovery was quantified seasonally over a 3-year post-restoration period using a suite of benthic macroinvertebrate measures.  Increases in biotic integrity from debris dam additions varied greatly among seasons, streams, and measures, resulting in large part because of unusually high precipitation and discharge during the post-restoration period, and associated high rates of sedimentation and debris dam burial in many sites.  Restored streams with high hydrologic flashiness, unstable stream beds, and associated high burial of debris dams (up to 75% in 6 mo) also were those showing the lowest amount of biotic recovery relative to less flashy streams possessing more stable channels and lower debris dam burial. Our data suggest that biotic recovery trajectories in these highly disturbed systems are a complex function of site-to-site variation in stream hydrology and geomorphology. If true, then accurate predictions of the effects of restoration may only be possible with an understanding of system-specific flow regimes and sediment movement dynamics.