隶属度判别法在水土流失快速评估中的应用

引入隶属度判别法对水土流失快速评估方法进行改进。在GIS的支持下,选取标准参照区域对反映水土流失状况的表现因子--输沙模数进行聚类,建立标准参照组,计算由各个环境因子特征值决定的水土流失对标准参照组的隶属度;采用特尔菲法确定选取的环境因子对表现因子的影响权重向量;对待测区域的环境因子进行分析,确定待测区域对标准参照组的隶属度矩阵和标准化隶属度向量;依据经验公式确定待测区域的输沙模数。以陕西省安塞县纸坊沟小流域为例进行了方法应用,结果表明该方法在小流域尺度上对输沙模数有较好的预测精度和较快的预测速度。

A Revised Fast Assessment Model for Soil Loss Based on Probabilities of Group Membership

Abstract: Currently,a fast method for soil loss assessment that uses rapid water quality evaluation method as reference has been proposed The core thought of the method is that areas with similar environmental factors should suffer similar soil loss Compared with existing methods for soil loss assessment such as USLE, which needs too much factor calibration, the fast method can produce soil loss degrees in areas without enough data Some steps can be improved and concrete models should be constructed if it is used to estimate the soil loss module In this paper, the fast assessment method for soil erosion is improved based on probabilities of group membership supported by Geographical Information System,which is introduced in this paper The improved method can be implemented with 8 successive steps: 1)clustering standard referring regions using representative factor which can be indicated by soil erosion modulus, 2)constructing standard reference groups of soil erosion, 3)matching the environmental factors of reference regions to standard reference groups and calculating their probabilities of group membership, 4)getting the weight of each land use/cover category to soil loss by Analytical Hierarchical Process, getting the weights of topographical factors to soil loss by existing studies, and getting the weights of soil erodibility by experiences, 5)using standard referring groups, probabilities of group membership, and weights of environmental factors to construct fast assessment model, 6)testing the model in statistical theory, 7)analyzing and calibrating the environmental factors of unknown regions, and 8)predicting soil erosion modulus in unknown areas A case application of the method was also carried out in Zhifanggou catchment, Yanhe watershed in North part of Shaanxi Province The soil erosion map was produced and it revealed that the soil erosion degrees and their spatial distribution is in agreement with the actual situation The USLE method was also used in estimating the soil erosion module for unknown areas The module calculated by the proposed method is very similar to that obtained by USLE However, the method carries some advantages in factor calibration and easy operation Though the case study in this paper is for a small basin,the method does not limit itself to small basin level If some appropriate environmental factors are selected and proper spatial units are adopted in dividing the target region.