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一、大砭沟流域概况 大砭沟位于延安北郊,东径109°32′,北纬36°36′,是延河的一级支沟,流域面积4.3平方公里,主沟长3.26公里,海拔900—1100米,沟道比降3.389％,流域呈椭圆形,内有小支沟8条,沟谷密度2.6公里/平方公里。上游沟床多乱石,下游沟床多冲积物。其地貌形态以峁边线为界,可分为两个区域,峁边线以上部位叫沟间地,以下部位叫沟谷地。 沟间地呈“梁”“峁”状的黄土丘陵,绝大部分为农耕地,分为梁峁顶和梁峁坡两部分。梁峁顶地面坡度多在3～8度,主要为水力侵蚀,侵蚀方式以溅蚀和细沟侵蚀为主。梁峁坡坡度为
I. Overview of Dazhougou Watershed Dazhougou is located in the northern outskirts of Yan’an with an east diameter of 109 ° 32 ’and a latitude of 36 ° 36’N. It is a grade-one branch of the Yanhe River and covers an area of 4.3 square kilometers with a main trench length of 3.26 kilometers and an elevation of 900-1100 meters, 3.389% lower than the channel, the basin was oval, there are 8 small branch trench, valley density 2.6 km / km2. More ditch upstream ditch bed, downstream ditch bed alluvial. Its topography is bounded by the border line, which can be divided into two areas. The area above the borderline is called ditch, and the following area is called the valley. Between the ditch was “beam” “峁” -like loess hills, the vast majority of agricultural land, divided into two parts beam ridge roof and beam slope. Beam top land slope mostly in 3 to 8 degrees, mainly for hydraulic erosion, erosion and sputtering to the main erosion rill. Beam slope slope for