Digital elevation models (DEMs) enable extraction of stream networks, delineation of watersheds and determination of geomorphological characteristics. A widely used method for stream network extraction is to specify a threshold area required to initiate a channel. This is achieved by applying a threshold area value (As) in GIS software which displays the accumulated flow to each cell. In this study, the effect of the assigned As on the direct runoff hydrographs was analyzed. Of using different threshold values varying in a wide range, stream network extraction and watershed delineation were performed, and then stream orders, main channel lengths and related morphometric parameters were computed. The geomorphological instantaneous unit hydrograph (GIUH) theory was adopted to obtain the hydrological response of the watershed and three direct runoff hydrographs were considered for validation. Statistical parameters and cumulative density functions of both observed and simulated hydrographs were computed and uncertainty analysis was performed. The best performing value of As with respect to the stream order and main channel length was determined using hesitant probabilistic fuzzy linguistic sets for different runoff hydrographs and criteria considered. It was found that the As value affected the stream order as expected and a stream order of maximum 3 was adequate for estimation of the runoff hydrograph with acceptable accuracy without unreasonably increasing the computational effort.

数字高程模型 (DEM) 能够提取河流网络、划定流域和确定地貌特征。一种广泛使用的流网络提取方法是指定启动通道所需的阈值区域。这是通过在 GIS 软件中应用阈值面积值 (As) 来实现的，该软件显示每个单元的累积流量。在这项研究中，分析了指定的 As 对直接径流水位线的影响。使用大范围变化的不同阈值，进行河网提取和流域划分，然后计算河道阶次、主河道长度和相关形态测量参数。采用地貌瞬时单位水位线（GIUH）理论获得流域的水文响应，并考虑了三个直接径流水位线进行验证。计算了观测到的和模拟的水文过程线的统计参数和累积密度函数，并进行了不确定性分析。使用犹豫概率模糊语言集为不同径流水位线和考虑的标准确定了与河流顺序和主渠道长度相关的最佳 As 值。发现 As 值影响了预期的河流顺序，最大 3 的河流顺序足以以可接受的精度估计径流水位线，而不会不合理地增加计算工作量。计算了观测到的和模拟的水文过程线的统计参数和累积密度函数，并进行了不确定性分析。使用犹豫概率模糊语言集为不同径流水位线和考虑的标准确定了与河流顺序和主渠道长度相关的最佳 As 值。发现 As 值影响了预期的河流顺序，最大 3 的河流顺序足以以可接受的精度估计径流水位线，而不会不合理地增加计算工作量。计算了观测到的和模拟的水文过程线的统计参数和累积密度函数，并进行了不确定性分析。使用犹豫概率模糊语言集为不同径流水位线和考虑的标准确定了与河流顺序和主渠道长度相关的最佳 As 值。发现 As 值影响了预期的河流顺序，最大 3 的河流顺序足以以可接受的精度估计径流水位线，而不会不合理地增加计算工作量。使用犹豫概率模糊语言集为不同径流水位线和考虑的标准确定了与河流顺序和主渠道长度相关的最佳 As 值。发现 As 值影响了预期的河流顺序，最大 3 的河流顺序足以以可接受的精度估计径流水位线，而不会不合理地增加计算工作量。使用犹豫概率模糊语言集为不同径流水位线和考虑的标准确定了与河流顺序和主渠道长度相关的最佳 As 值。发现 As 值影响了预期的河流顺序，最大 3 的河流顺序足以以可接受的精度估计径流水位线，而不会不合理地增加计算工作量。