Data for "Disturbance and valley confinement: controls on floodplain LW and organic matter jam deposition in the Colorado Front Range, USA"

Organic matter dynamics (entrainment, transport, deposition) can influence ecogeomorphic complexity in rivers. However, the depositional controls on downed, large wood (LW) and coarse particulate organic matter (CPOM) on floodplains have rarely been assessed. We investigate the influence of different disturbance histories, as well as geomorphology and forest stand density, on the deposition of LW and CPOM accumulations, or jams, between two adjacent drainages (West Creek, North Fork Big Thompson) in the Colorado Front Range. Both basins recently experienced an extreme flood, but West Creek experienced a larger flood peak as well as a recent upstream fire. We also analyse jam fabric (LW piece orientation) between floodplain and in-channel jam types. We measured LW and CPOM jams on the North Fork to compute jam frequencies (jams ha-1) and loads (m3 ha-1), and we compare these data to a previously published dataset from West Creek. Average LW jam frequencies (70.4 jams ha-1) and loads (678.6 m3 ha-1) on West Creek were significantly higher than on the North Fork (frequency: 14.8 jams ha-1; load: 94.3 m3 ha-1). Average CPOM jam frequencies (West Creek: 19.0 jams ha-1; North Fork: 15.1 jams ha-1) and loads (West Creek: 10.70 m3 ha-1; North Fork: 9.98 m3 ha-1) were not significantly different between basins. A larger flood peak, likely enhanced by a recent upstream fire and a more confined valley bottom, resulted in greater deposition of LW jams on West Creek compared to the North Fork. Confinement played an additional role in controlling jam deposition, where a wider valley bottom resulted in reduced jam frequencies and loads. Floodplain jam types oriented parallel to the stream were significantly than other jam types. This work will inform river restoration efforts in semi-arid regions and provide concrete examples of how LW deposits on floodplains for numerical models that incorporate LW.

The data was collected as part of research for the following manuscript:

Guiney, M.R., & Lininger, K.B. (2021). Disturbance and valley confinement:controls on floodplain large wood and organic matter jam deposition in the Colorado Front Range, USA [Manuscript submitted for publication]. Department of Geography, University of Colorado Boulder