LONG TERM EFFECTS OF UPLIFT ON THE DEVELOPMENT OF EXPERIMENTAL EROSION LANDFORM

Miniature experimental erosion landform was developed by applying artificial rainfall on the square mound of a mixture of fine sand and kaolinite (ca.90x90x12cm). The mound was slowly uplifted after the surface became low relief (255 hours of rainfall). The slow uplift (ca. 0.1mm every 3 hours) was continued to the end of the experiment (1749 hours). The total amount of uplift is about 60 mm. The average height lowered exponentially at first but its rate decreased significantly after the uplift started. From 255 to 853 hours of rainfall the average height showed only slight decrease. When the amount of uplift is subtracted, the change in average height in this period shows an exponential decrease continuous from the decrease before the uplift. This indicates that the surface was uplifted without significantly affecting the rate of erosion. The height of lowest points, which indicate the bottom height of main valleys, decreased rapidly at the beginning and then slowly decreased. After the uplift started, the lowest height kept nearly the same level with some ups and downs until 853 hours. The main valleys could easily keep the bottom height against the uplift of this rate, and the prolonged development of alluvial fans around the mound helped to keep the local base level for a longer time. The rate of average height lowering clearly increased after 853 hours with the development of one dominated drainage area and the cessation of alluvial fan development. The bottom height of the main valley also lowered with dissecting the alluvial fan. The height of highest points, which represents the height of ridges, decreased slowly at first and then with the increased rate. Its change was not affected by the uplift so much as the average height, but it slightly increased with the uplift after 853 hours. The overall relief increased towards the end of experiment while the local relief did not show a clear change. The slow uplift could not lift up the entire experimental erosion landform against the erosion, but it helped to keep the average height at a higher level while the development of alluvial fans kept the local base level. It also helped the remaining high points stay higher, after the large drainage area dominated the surface and the average height lowered against the uplift.