The relationship of hilslope erosion rates and sediment yield is often poorly defined because of short periods of measurement and inherent spatial and temporal variability in erosion processes. In landscapes containing hillslopes crenulated by alternating topographic noses and hollows, estimates of local hilslope erosion rates averaged over long time periods can be obtained by analysing colluvial deposits in the hollows. Hollows act as local traps for a portion ofthe colluvium transported down hilslopes, and erosion rates can be calculated using the age and size of the deposits and the size of the contributing source area. Analysis of colluvial deposits in nine Oregon Coast Range hollows has yielded average colluvial transport rates into the hollows of about 35 cm -1 yr -l and average bedrock lowering rates of about 0,07 mm yr -1 for the last 4000 to 15000 yr. These rates are consistent with maximum bedrock exfoliation rates of about 0,09 mm yr -1 calculated from six of the hollows, supporting the interpretation that exfoliation rates limit erosion rates on these slopes. Sediment yield measurements from nine Coast Range streams provide similar basin-wide denudation rates of between 0,05 and 0,08 mm yr -1 , suggesting an approximate steady-state between sediment production on hilslopes and sediment yield. In addition, modern sediment yields are similar in basins varying in size from 1 to 1500, suggesting that erosion rates are spatially uniform and providing additional evidence for an approximate equilibrium in the landscape.
We use a record of sedimentation in a small reservoir within the Cerro Grande burn area, New Mexico, to document postfi re delivery of ash, other fi ne-grained sediment carried in suspension within fl oods, and coarse-grained sediment transported as bedload over a fi ve-year period. Ash content of sediment layers is estimated using fallout 137 Cs as a tracer, and ash concentrations are shown to rapidly decrease through a series of moderate-intensity convective storms in the fi rst rainy season after the fi re. Over 90% of the ash was delivered to the reservoir in the fi rst year, and ash concentrations in suspended sediment were negligible after the second year. Delivery of the remainder of the fi ne sediment also declined rapidly after the fi rst year despite the occurrence of higher-intensity storms in the second year. Fine sediment loads after fi ve years remained signifi cantly above prefi re averages. Deposition of coarse-grained sediment was irregular in time and was associated with transport by snowmelt runoff of sediment stored along the upstream channel during short-duration summer fl oods. Coarse sediment delivery in the fi rst four years was strongly correlated with snowmelt volume, suggesting a transport-limited system with abundant available sediment. Transport rates of coarse sediment declined in the fi fth year, consistent with a transition to a more stable channel as the accessible sediment supply was depleted and the channel bed coarsened. Maximum impacts from ash and other fi negrained sediment therefore occurred soon after the fi re, whereas the downstream impacts from coarse-grained sediment were attenuated by the more gradual process of bedload sediment transport.
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