HR: 09:30h
AN: H51H-07    [Abstracts]
TI: Road Connectivity and Sediment Yields in Forested Landscapes
AU: * MacDonald, L H
EM: leemac@cnr.colostate.edu
AF: Watershed Science Program, Colorado State University, Fort Collins, CO 90523-1472, United States
AU: Coe, D B
EM: dbrcoe@waterboards.cal.gov
AF: Regional Water Quality Control Board, 415 Knollcrest Drive, Redding, CA 96002, United States
AU: Welsh, M
EM: mwelsh@cnr.colostate.edu
AF: Watershed Science Program, Colorado State University, Fort Collins, CO 90523-1472, United States
AU: Korte, A M
EM: amkorte@lamar.colostate.edu
AF: Watershed Science Program, Colorado State University, Fort Collins, CO 90523-1472, United States
AU: Brown, E
EM: ethanbr@lamar.colostate.edu
AF: Watershed Science Program, Colorado State University, Fort Collins, CO 90523-1472, United States
AB: Unpaved roads are often considered to be the predominant sediment source in forested catchments, but catchment-scale studies generally have not been able to document a road-related increase in runoff or sediment yields. This discrepancy may be due to the proportion of roads that are connected to the stream channel network. This paper summarizes the results of three multi-year studies in California and Colorado that have investigated both road sediment production and the connectivity of roads to the stream channel network. Annual sediment production rates averaged around 3-8 Mg per hectare of road surface in California and 34 Mg ha-1 in Colorado. In both areas sediment production can be predicted from road segment slope, road surface area, and rainfall intensity or erosivity. In California 25 percent of the road length was connected to the stream channel network, and the majority of the connected segments were due to stream crossings. In Colorado only 14 percent of the road segments were connected, and most of the connected road segments were in the valley bottoms and connected by gullies or sediment plumes. An analysis of published data shows that 92 percent of the variability in road connectivity can be explained by mean annual precipitation, and the absence of engineered drainage structures increases the amount of road connectivity by about 40 percent. In Colorado the predicted sediment yields from unpaved roads are comparable to the sediment from high severity wildfires. In the southern Sierra Nevada of California roads accounted for less than 10 percent of the measured sediment yields in two small experimental catchments and 25-50 percent of the sediment yield in a third catchment. We conclude a relatively few road segments are responsible for most of the road-related sediment at the catchment scale, and that information on both sediment production and road connectivity are needed to identify the road segments of greatest concern and highest priority for remediation.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1815 Erosion
DE: 1862 Sediment transport (4558)
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Joint Assembly