Abstract
Flume experiments with permeable rubber sponge attached to the base were conducted to determine the sediment filtering function of simulated forested hillslopes by placing litter on the sponge and collecting runout and subsurface drainage. The efficiency of the sediment filtering function of all litter treatments degreased linearly as the amount of cumulated sediment increased. When thinking that sediment filtering occurs respectively in surface runoff and in the sponge, the suspended sediment in surface runoff was not affected by turbid water flowing into the sponge base or the initial permeability of the sponge, but rather the presence of litter and gradient. The filtering function of the sponge was not affected by the experimental surface conditions (e.g. litter amount), and was influenced only by the initial conditions within the sponge. Therefore the filtering function of forested hillslopes involve not only the soil, but also litter because litter trapped at least two times the sediment compared to no litter cover.
