HR: 1340h
AN: H53B-1229    [Abstracts]
TI: Wood Loading in Tropical Forested Headwater Streams
AU: * Cadol, D
EM: cadol@cnr.colostate.edu
AF: Colorado State University, Department of Geosciences, Fort Collins, CO 80523-1482, United States
AU: Wohl, E
EM: ellenw@cnr.colostate.edu
AF: Colorado State University, Department of Geosciences, Fort Collins, CO 80523-1482, United States
AB: The influence of wood on forested headwater streams has been explored in numerous studies conducted in temperate climate zones. As of yet few studies reported in the literature have expanded the research into other climate zones, and it is unclear which, if any, generalizations about wood-channel interactions will hold beyond the temperate zone. In this study we start to address this knowledge gap by characterizing wood loads in forested headwater streams located in the steep eastern foothills of the Central Volcanic Cordillera of Costa Rica. In surveys of 30 reaches, each 50 m long, we found the mean wood load to be 188 m³/ha (or 12.5 m³/100 m), with loads ranging from 41 to 612 m³/ha (3.0 to 34.7 m³/100 m) among the 30 study reaches. In each of the 30 study reaches we measured contributing drainage area, stream gradient, bedform roughness as quantified by the mean square error of the thalweg elevation, intermediate diameter of the 84th percentile bed material, grain sorting measured with the inclusive graphic standard deviation, average bankfull width, width to depth ratio, average valley slope, maximum valley slope, sinuosity, a surrogate for stream power, and a surrogate for unit stream power. Multiple regression analysis indicates that although no single variable adequately explains wood loading, more adequate models involving five significant variables can be constructed using best subset model selection with Mallows' Cp as the selection criterion. Variable subsets used to model wood volume per 100 m of channel and wood volume per hectare of channel differ slightly, but both have R- square values near 0.5 and adjusted R-square values of approximately 0.4. Additionally, both utilize drainage area, slope, and stream power, indicating that transport of wood through the channel network is likely to be an active and influential process in controlling wood load. Drainage area is positively correlated with wood load, suggesting that channels with large contributing networks are more likely to have large wood loads. Slope, stream power, and unit stream power are negatively correlated with wood load, suggesting that channels with an increased capacity to transport wood have lower wood loads. Channel width is a significant component of the model of wood load per hectare, but not of the model of wood load per 100 m of channel. Wider channels correlate with lower wood volumes per hectare, but with slightly higher wood loads per 100 m of channel.
DE: 0483 Riparian systems (0744, 1856)
DE: 1813 Eco-hydrology
DE: 1825 Geomorphology: fluvial (1625)
DE: 1880 Water management (6334)
SC: Hydrology [H]
MN: 2007 Fall Meeting