Determination of soil losses using the geographical information system (GİS) techniques and the rusle method in Bursa Madan River Basin

This research was carried out to determine the amount of soil losses by using GIS techniques and RUSLE method in different land use types in the Madan Stream Basin in Osmangazi district of Bursa. Within the scope of this purpose, 120 points were determined to include different land uses (forest, agriculture, pasture). A total of 120 degraded soil samples and 120 undisturbed cylinder samples were taken, 60 from forest, 40 agriculture and 20 pasture areas. On soil samples taken from the field; texture, soil reaction and organic matter content analyzes were made. In the study, the amount of erosion occurred in the Madan Stream Basin was determined by using GIS techniques and RUSLE model. As a result of the values obtained as a result of the RUSLE model parameters, it was determined that the mean value for the R factor was 820.65, the mean value for the K factor was 0.0275, the mean value for the LS factor was 1.67, and the C factor value ranged between 0 and 0.07. In the Madan Stream basin, the annual erosion amount calculated in different land uses (forest, agriculture, pasture) according to the RUSLE method was determined as 17.42 tons in pasture areas, 1695.42 tons in agricultural areas and 281.82 tons in forest areas. In the Madan Stream basin, the sediment transmission rate was calculated as 0.40 tons per hectare and this calculated value means the transportation of the soil. According to the data obtained, while 1995,4 tons of soil is mobilized as a result of erosion; 798.16 tons of soil reaches streams. This value means transporting 0.35 tons of soil per hectare per year. Soil loss according to land use was calculated as 0.35 tons/ha/year in pasture areas, 0.95 tons/ha/year in agricultural areas and 0.07 tons/ha/year in forest areas. According to the RUSLE method, the most erosion occurred in agricultural areas, while the least erosion occurred in forest areas. The abundance of agricultural activities in the study area has destroyed the natural vegetation and caused soil loss in the basin. In conclusion; It can be said that if necessary precautions are not taken in the basin, the severity and amount of erosion will increase. Practices that may cause soil loss in areas at risk of erosion should be avoided and control efforts should be made to expand around the Madan Stream basin by initiating efforts to combat erosion.