Surface sediment transport: a review of current knowledge and a field study of its spatial and temporal distributions in the San Dimas Experimental Forest, California

Includes bibliographical references (pages 191-216)Surface sediment transport, the grav1ty induced downslope\ud movement of the surficial veneer of soil material, is a\ud significant denudational activity in southern California\ud watersheds. A review is presented summarizing the current\ud knowledge of the pertinent processes, mechanics, controls,\ud and effects of hillslope denudation. A thirteen month\ud field study using 30 cm aperture collection troughs analyzed\ud the influence of slope aspect, hillside steepness, and\ud Vegetation type on the distribution in space and time of\ud surface sediment transport in the San Dimas Experimental\ud Forest. Results indicate that, despite extremely variable data,\ud vegetation type is a highly significant factor in controlling\ud total surface sediment transport while slope aspect signiticantly\ud affects the spatial distribution of mineral matter\ud movement. Hillside steepness and vegetation type affect\ud the temporal distribution of mineral debris production.\ud An analysis of rainfall and wind travel data indicates\ud that surface sediment transport is more closely related\ud to blowing wind than to falling rain. There is no apparent\ud difference in surface transport between upslope and downslope\ud plots with identical site characteristics. Recovery patterns\ud of colored tracer particles reinforce the disparity in\ud spatial debris production figures from plots with ditferent\ud vegetation assemblages. These results lead to the conclusion that the entire\ud surface veneer of the slope mantle is moving together as\ud a quasi-continuous mass by sequential downslope sediment l\ud transport. The manners of action of the operative surface\ud processes coupled with the field data suggest that declining\ud retreat is the most probable mode of slope development\ud within the San Dimas Experimental Forest