Investigation of land use change effect on runoff and soil erosion using rainfall simulation in Heiran area, Ardabil

Soil and water are the most valuable national resources. Unfortunately in recent decade, due to land use change and vegetation cover degradation, most of the rainfall changed into runoff and in addition to loss of this vital resource, causes abundant loss of life and property by creating enormous floods. The aim of this study is to assess the effect of land use change from range land to agriculture with different percent of vegetation cover on runoff and soil erosion. For this purpose, three types of land use included preserved range land with 100 percent of vegetation cover; range land with 50 percent of vegetation cover and agricultural land (range land changed to agriculture) were identified in the study area. Then, in each land use, three slopes were determined (10, 15 and 24%). This study was carried out split plot experiment based on completely randomized design. In each land use and slope, runoff and erosion were measured in plots randomly using rainfall simulator with 1.5 mm.min-1 intensity and 15 min duration with 3 replicates. Results showed that the maximum of runoff, sediment mass and sediment density were in the range land changed to agriculture with 24% slope and the minimum of them were in the preserved range land with 10% slope. Also the results showed that the change of range lands to agricultures increase runoff 5 times. In the other hand, with increasing slope from 10 percent to 24 percent, runoff increased 1.7 times. Runoff coefficient was determined for 3 land uses and 3 slopes level. The maximum and minimum runoff coefficient were found 0.72 and 0.06 for the range land changed to agriculture with 24% slope and preserved range land with 10% slope, respectively.