Slope length effect on sediment and organic litter transport on a steep forested hillslope: upscaling from plot to hillslope scale

Upscaling and the effect of slope length on the sediment production are important issues in hillslope hydrology. This study investigated the effect of slope length at a steep forested site between 2006 and 2010 using erosion plots and neighboring sediment traps. The hillslope had high litter cover but sparse understory due to overgrazing by wild deer. Sediment transport increased for short distances (5 m to 10 m), then decreased over the hillslope (> 10 m). In plots this effect was due to organic litter accumulation. Organic litter production declined progressively along the hillslope continuum. When accumulated organic litter altered the microtopography, sediment production declined more with increase in slope length. Heavy precipitation events did not change the pattern of these scale effects. These results demonstrate that the slope length effect had inconsistent controls on sediment transport due to variations in soil surface conditions of the landscape. Such variations in the slope length effect cause uncertainty in sediment flux estimations in steep forested landscapes.