Water Resources Research Act Program

Principal Investigators: Katherine Lininger

Abstract: Large downed wood (LW) significantly influences river corridor (channel and floodplain) ecology and morphology, providing sites of seedling establishment and influencing channel planform. In-channel LW can also be considered a hazard, with the potential to cause structural damage to dams and bridges. Floodplain LW may be less mobile, providing an opportunity to use LW to enhance ecological benefits while minimizing hazards. While extensive research has been conducted on in-channel LW, significant knowledge gaps exist regarding LW on floodplains. I seek to better understand sourcing and depositional characteristics of floodplain LW by utilizing dendrochemistry, conducting field surveys, and performing GIS and statistical analyses. I will conduct research on West Creek near Glen Haven, Colorado. West Creek is a small mountain tributary within the Big Thompson drainage basin of the Colorado Front Range. West Creek experienced severe impacts from the 2013 flood event, resulting in significant deposition of LW into accumulations, or jams. These jams have not been modified since the flood event. I will take cores of living trees and LW in jams in varying spatial locations along the river corridor, and the sampled wood will then be analyzed on a mass spectrometer to determine isotopic compositions. I will compare the isotopic signature of living hillslope and valley bottom trees with the signature of LW in jams, resulting in an assessment of the source of LW in jams (e.g., valley bottom or hillslope). I hypothesize that significant differences in isotopic composition, or variability in composition, will exist between hillslope and valley bottom trees, allowing for a determination of the source of LW in jams. At selected locations representative of different depositional environments (e.g., near-channel, distal from the channel, etc.), I will measure the orientations of LW pieces in jams. I hypothesis that floodplain LW will largely deposit in orientations parallel to flow. LW pinned on trees on the floodplain may exhibit orientations normal to flow. Results from this work will impact the use of floodplain LW for restoration and management.