Evaluation of freeze-thaw erosion in Tibet based on the cloud model

Freeze-thaw erosion can lead to accelerated soil loss, which is an important factor related to soil erosion in cold regions. Tibet is a typical region that is seriously affected by freeze-thaw erosion. Traditionally, the analytic hierarchy process (AHP) method is used to calculate the weight of the factors in evaluations of freeze-thaw erosion, but this method cannot accurately depict the fuzziness and randomness of the problem. To overcome this disadvantage, this study proposed an improved AHP method based on the cloud model for the evaluation of the factors impacting freeze-thaw erosion. To establish an improved evaluation method for freeze-thaw erosion in Tibet, the following six factors were selected: mean annual air temperature, mean annual ground surface temperature, average annual precipitation, aspect, vegetation coverage, and topographic relief. The traditional AHP and the cloud model were combined to assign the weights of the impacting factors, and a consistency check was performed. The comprehensive evaluation index model was used to evaluate the intensity of freeze-thaw erosion in Tibet. The results show that freeze-thaw erosion is extensive, stretching over approximately 66.1% of Tibet. Moreover, mild erosion and moderate erosion are the most widely distributed erosion intensity levels, accounting for 36.4% and 34.4% of the total freeze-thaw erosion, respectively. The intensity of freeze-thaw erosion gradually increased from slight erosion in the northwest to severe erosion in the southeast of the study region. The evaluation results for the intensity and distribution of freeze-thaw erosion in Tibet were confirmed to be consistent with the actual situation. In brief, this study supplies a new approach for quantitatively evaluating the intensity of freeze-thaw erosion in Tibet.