EFFECTS OF UPLIFT RATE ON THE DEVELOPMENT OF EXPERIMENTAL EROSION LANDFORM

Experimental erosion landform developing with artificial rainfall (ca. 38 mm/h) on the square mound of a fine sand and clay mixture (ca. 90x90x15cm) was uplifted after the peneplain-like landform developed (255 hours of rainfall). Two Runs, Runs 10 and 13, with different uplift rates were performed to see the effect of uplift rate on the development of experimental erosion landform. The uplift rate was about 0.5mm/h for Run10 and about 0.04mm/h for Run13. In Run10, the average height increased at a reduced rate during the uplift, while it decreased exponentially before and after the uplift. The erosion apparently could not keep up the average height against the uplift of this rate. Both the minimum and the maximum heights also increased with the uplift, but the rate of increase was higher for the maximum height; and therefore, overall relief increased. In Run13 the average height continued to decrease after the uplift started, but this changed to a slight increase or no decrease after about 160 hours of uplift (6.4mm) and rainfall. The maximum height accelerated its decrease and the minimum height decreased at first and then slightly increased, after the uplift started. In Run13, which requires much longer time to complete, the average height would attain a state of equilibrium with the slow uplift and the minimum height would stay around a certain value due to the fixed base level of erosion. The maximum height gradually decreased at first, but it would increase to a certain degree in a long period of uplift. This suggests that relief can increase as far as the uplift continues even if the rate is very small. Zi, which is the standard deviation of heights in a 10x10cm square, increased significantly with the uplift in Run10, but did not change with uplift in Run13, while Hf, the parameter expressing the self-affinity of surfaces, shows similar changes in both Runs. The results of experiments suggest that rapid uplift increase both the average height and relief, and slow uplift keep the average height but tend to maintain certain relief.