Understanding intra-catchment processes related to management of tropical headwater catchments

Abstract

Various intra-catchment processes were studied in two neighboring tropical headwater catchments of Peninsular Malaysia: a relatively undisturbed catchment (C1) and a catchment severely disturbed by logging activities (C3). Hydrochemical monitoring of a zero-order basin (ZOB) within C1 indicated that subsurface flow accreted above the soil-saprolite interface provided a major stormflow component with soil pipes facilitating rapid flow delivery. In comparison with planer hillslope and riparian floodplain, ZOB was hydrologically the most dynamic and played a disproportionately important role in exporting solutes such as nitrate. Road surfaces in C3 altered catchment hydrology by promoting overland flow. In addition, road cuts transformed subsurface flow to overland flow during relatively large events, resulting in additional road surface erosion and bypassing of solute-rich flow downslope of the roads. Lastly, absence of vegetation on the road surface likely caused continuous, excessive surface erosion, which eventually became ameliorated by road-side fern growth.