| To get a better idea of hilly road erosion in the loess hilly-gully region and the current of road distribution, the survey statistics of land utilization and road distribution in Yangou valley was conducted by field delineation, the road density parameter was fixed and the road demand was simply predicted after image processing, data statistics and regression equation setting by GIS software, based on monitoring Yangou valley of Yan'an in the loess hilly-gully region and the field investigating, the influence of hilly road erosion and the benefit of road erosion measures were analyzed.(1) Investigation of road density in Yangou valley, the following conclusions:For road density within the village domain parameters, We propose todeploy the 5.2 km/km2 in land, 3.9 km/km2 in orchard,2.47 km/km2 in woodland.For road density within 1km parameters, We propose todeploy the 7.61 km/km2 in land, 6.38 km/km2 in orchard,3.6 km/km2 in woodland.We propose todeploy the 6.75 km/km2 in land,5.81 km/km2 in orchard,5.04 km/km2 in woodland.It shows the average value of rode density is 5.07 km/km2 on village boundaries in yangou valley.(2) According to the characteristics of hilly road erosion, comprehensive configuration of hilly road erosion measures was as follows:Side slope was protected by tamping, grading angle rational design. Flow distribution and plant measures, arch pavement was adopted with intercepting drain, catch basin and water pit leading and damming the flow from the roads, and culvert leading the road across ditch. Agropyron cristatum (L) gaertn, Lespedeza bicolor Turcz and Bromus inermis Leyss et native grass seeds were selected to be grown on plant roads. Tagetes erecta, Hippophae rhamnoides L, Rosa xanthina Lindl, Ostryopsis davidiana and wild grass-shrub mixture were celected to be grown on side slopes. (3) The benefit analysis of corrosion prevention measures of hillside path is as follows, under the hypo-rainfall intensity, plot with the side slope vegetation degree of cover achieved 70% is reduced 24.5-72.9%, comparing to which the side slope vegetation degree of cover is 0, the section erosion modulus of roadside construction had reservoir's road section reduced 55% comparing to the non-reservoir road, the erosion modulus of kiln cellar road section reduced 80% comparing to which of the non-kiln cellar road section, the erosion modulus of the plant measure protection road section reduced 40%-62% comparing to the exposed earth road section, the average erosion modulus of the reservoir road section which had the transversal grade grass belt reduced 82% comparing to the exposed road section.(4) By the preliminary calculations on the road erosion, the conclusions are:rode erosion reaches to 51096.6 t a whole year in yangou valley. If the road corrosion measures post perfectly, it will decrease erosion 28103.13～to 40877.28 t every year to the yangou valley.This article initially discusses the road erosion control and road density manufacturing, and also gives a reference for the new rural roading and the road erosion control.
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