Colorado State University

Wood in river corridors (channels and floodplains) strongly influences geomorphic and ecological processes, but wood dynamics in floodplains have received relatively little attention compared to wood in channels. Floodplain wood influences floodplain hydraulics, patterns of sedimentation, organic carbon storage, and habitat for biota. However, we lack understanding of how geomorphic characteristics and riparian forest stand density influence wood transport, deposition, and storage on floodplains. I present results from field-based studies and physical experiments that shed light on floodplain wood and organic matter dynamics. The field-based studies demonstrate that large floods (e.g., the September 2013 flood on the Colorado Front Range) can deliver significant floodplain storage of wood and organic matter. Results indicate that reach-scale slope, forest stand characteristics, and watershed disturbance history influence the load (m3 ha-1) and frequency of wood and organic matter accumulations (i.e., jams). Using the field sites as prototypes, we conducted physical experiments in a 4m x 9.75m fixed bed flume to assess how variations in flood magnitude, forest stand density, and the amount of wood in transport influence floodplain wood deposition. I present preliminary results from 21 trails across 8 experimental setups. Our flume experiments demonstrate that increasing forest stand density resulted in a higher proportion of wood pieces retained in the flume (in the channel and floodplain). However, high forest stand density also resulted in a lower proportion of retained pieces on the floodplain. In addition, lower forest stand density resulted in larger floodplain jams. This work enhances knowledge of ecogeomorphic processes in river corridors, with implications for river restoration efforts aimed at promoting river corridor physical complexity and increasing organic carbon storage.