10 Despite the amount of uncertainty placed on these volume–weig

10. Despite the amount of uncertainty placed on these volume–weight calculations it appears

OSI-906 concentration that published C-factors nonetheless underestimate the effects of urban forest cover in the region ( Fig. 11); however, in order to elucidate an appropriate C-value range for the area, an assessment of the contributions to the pond’s sediment budget unaffiliated with sheet and rill erosion from the surrounding landscape is required. The following two sources offer explanation for the inclusion of materials not accounted for by the USLE, which contribute to the overestimation of pond sedimentation due to inter-rill and rill processes: (1) sediment transported into the pond by anthropogenic means, and (2) gully erosion from surrounding hillsides. The pond is the final resting place for 17-AAG chemical structure all materials derived from surrounding hillslopes and the footpath. A small source of error that could explain some of the variance between field and numerical model results is presented by the unknown factors associated with the upkeep of the footpath around the pond. Sand and gravel are replaced here on a regular basis as hillslope runoff not only carries materials from the slopes,

but also from the footpath into the pond. Evidence for this process is found in cores, which contained scattered pebbles found concentrated on the footpath. Since no records exist that would allow for quantification of this sediment source, the extent to which very these materials

offset measurements cannot be pursued; however, based on an assessment of collected sediment cores and a comparison of pond-sediment volume against path dimensions, it is assumed this contribution is negligible. It is likely that gullies are a significant contributor to the USLE model deviation; however, they provide an unquantified volume of sediment to the pond’s budget and pursuing their contribution from a process-oriented perspective would be time-consuming. It is estimated based on field reconnaissance of gully dimensions (width and depth) and their extent (derived from the flow-accumulation model) that the volume represented by gullies along the steep slopes north of the pond corresponds to ∼100 m3. This Gully-volume estimate is an order of magnitude smaller than the volume of sediment emplaced into the pond (∼6228 m3) and therefore would do little to close the gap between USLE model estimates of inter-rill and rill erosion and quantified pond sedimentation (Fig. 11). Regardless of how much gullying and anthropogenic contributions may add to the pond’s sediment budget, evidence suggests that urban forest cover promotes high erosion rates, which translate to high sediment flux and deposition within the pond. This is a function of the absent sediment storage anywhere along route within the watershed (Fig. 3); the study area thus provides a suitable location for a qualitative assessment of the C-value for this land-cover type.

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