通过GPS野外实测黄土高原纸坊沟小流域的道路特征,在GIS空间分析等方法支持下研究了流域内各级道路的分布规律。研究表明:黄土高原道路可分为4级,2级以下的土路是小流域的代表路型。各级别道路总长度都随级别增大而增加且累计总长度与道路级别线性相关,道路平均长度和密度则随级别增大而减小。道路网系和流域水系在结构规律上具有一定的相似性。不同级别道路分布范围受地形特征影响不同。爬坡道路坡度与地表坡度之间存在线性回归关系,且次级道路分布受主路控制;典型爬坡路在大于25°坡度范围内多呈"之"字形弯曲,随坡度的减小道路弯曲跨度和与等高线夹角增大。研究结果有助于定量模拟黄土高原地区道路分布特征,并为土壤侵蚀模型中道路影响因子的确定提供参考。

An agricultural watershed generally consists of farmland and road networks, of which unpaved roads are a significant land use type in rural watersheds. Road surfaces are quite different from farmland soil in physical properties, compared with farmlands, road surfaces may limit infiltration and increase the rate of sediment yield in watershed. Also, road networks can influence and change hydrologic and geomorphic processes greatly in a watersheds. Hence, roads distribution patterns should be taken into consideration in soil loss prediction models as crucial factors. In order to explore the spatial distribution characteristics of roads in small watersheds of the Loess Plateau, a field survey was conducted in the small watershed of Zhifanggou located on central Loess Plateau to get roads network data with the aid of GPS in the study. On the basis of field data and DEM of Zhifanggou watershed, GIS spatial analysis and statistical methods were used to analyze road network in view of their quantity, structure and morphology respectively as well as controlling factors. The results showed that roads on Loess Plateau could be classified into 4 types based on their functions and scales. Unpaved roads of classs 2, 3 and 4 are representatives in small watersheds. Total road lengths are linearly related with road classes. Roads network was similar to the stream networks in construction and could be described by Horton laws. Generally, road construction was controlled by landforms and human activities, roads controlled by landforms were distributed along main road and total length changed as exponential function of distance from the main road. Roads that are relatively freely-distributed are mainly in zones of the same elevation with residential zones. Linear relationship exists between the slope gradient sine values of road controlled by landform and that of land surface. Based on which the mean angle between road and contour can be calculated as 29.3. The microcosmic features of roads were different on surfaces of different slopes. Both the curve span and the angle between road and contour are increased with the decrease of slope gradients. Zigzag rarely happens and roads nearly upright with contours when slope is less than 25 . This study will be helpful in a good understanding of road network characteristics in a watershed and can provide powerful supports to the establishment and application of process-based models which estimate the effects derived from road networks on runoff and soil loss in watersheds.