Measured hillslope erosion rates in the wet-dry tropics of Cape York, northern Australia Part 1: A low cost sediment trap for measuring hillslope erosion in remote areas - Trap design and evaluation

Sediment budget modeling has become a widely used management tool for setting priorities for natural resource management in Australia and globally. Two of the most widely used models in Australia, SedNet, and its more recent successor Source Catchments, rely on the Revised Universal Soil Loss Equation (RUSLE) to predict sediment production from hillslope erosion. In Australia, however, very little empirical data exists with which to test the hillslope sediment yields predicted by the RUSLE, particularly in the more remote savannah woodlands of northern Australia that are used by the cattle grazing industry. These savannah woodland landscapes comprise the vast majority of the catchment area draining into key ecological assets such as the Great Barrier Reef lagoon. In this paper we present the design and evaluation of a simple, low cost hillslope sediment trap (HST) that requires little to no maintenance across an entire wet season. It can consequently be deployed in remote, inaccessible areas to collect sediment generated through hillslope erosion processes as a means of testing predictions of erosion. Using these traps, it is possible to develop locally calibrated hillslope erosion models that will provide far more realistic predictions of erosion than have previously been employed. Laboratory flume evaluations of the HSTs also show that the traps will accurately sample the full particle size distribution of sediment mobilized on a given hillslope, with a suspended sediment (< 63 μm) trapping efficiency conservatively estimated to be 50%.