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[目的]2017年7月25日20时到26日8时陕北榆林地区突降了一场特大暴雨,造成了严重的洪水灾害与经济损失。通过考察该次暴雨造成的土壤侵蚀危害,旨在为今后该区水土流失治理及暴雨灾害的防御提供依据。[方法]于2017年8月2—6日赴暴雨受灾区子洲县,选取了清水沟、马家沟、蛇家沟3个典型小流域作为重点调查区域,对该次暴雨下流域内坡耕地、退耕林草地、梯田、填沟造地、淤地坝、道路等的土壤侵蚀特征进行了调查与分析。[结果]在“7·26”特大暴雨洪水下,坡耕地细沟发育明显,甚至产生小切沟;而2000年退耕的林地和自然恢复草地以面蚀为主,无明显细沟产生;新修梯田连接两阶田面的道路及承接路面来水的田面冲毁严重,田埂部分区段被冲开,田坎发生塌落;在削坡填沟造地区域,不仅农作物和坝体遭到严重破坏,而且残蚀了田旁新修道路,切割裸露沟壁多处发生土体塌落;淤地坝或轻或重都存在损毁与隐患,但在该次暴雨中滞洪拦沙作用明显。同时,在调查中发现该区陡坡耕种现象依然存在,小流域蓄排水系统缺乏,部分水土保持工程管理与维护不到位,经济发展水平低,农民水土保持意识淡薄。[结论]“7·26”特大暴雨洪水造成的土壤侵蚀依然很严重,而退耕林草地的土壤侵蚀轻微,证明水土保持工作在该区依然十分重要。在生态环境脆弱的陕北黄土高原地区,应该继续加强环境保护措施,加大水土保持治理力度,特别是陡坡退耕。同时,专业设计并实施小流域蓄水、引水、排水网络系统十分必要。
[Objective] From 20:00 on July 25, 2017 to 8:00 on the 26th, a sudden heavy rainfall caused a serious flood disaster and economic loss in the Yulin area of northern Shaanxi. By investigating the harm of soil erosion caused by this heavy rainstorm, this paper aims to provide the basis for future soil erosion control and rainstorm disaster prevention in this area. [Method] Three typical small watersheds, Qingshuigou, Majiagou and Snakejiagou, were chosen as the key areas for investigation in Zizhou County from August 2-6, 2017, , Returning farmland to forest and grassland, terraced fields, landfill construction, silt dam, roads and other soil erosion characteristics were investigated and analyzed. [Result] Under the severe rainstorm of “7 · 26”, the development of fine gully in sloping farmland was obvious, and even small cutting ditches were produced. In 2000, the forestland and natural grassland for returning farmland were dominated by surface erosion, ; Newly repaired terraces connecting the two-stage surface of the road and to undertake the pavement surface water washed away seriously, some parts of the ridge was washed open, Tian ridge collapse; in the cut slope trench construction area, not only crop and dam were Serious damage, and the erosion of the field next to a new road, cutting the exposed ditch wall occurred in many places slump; silt dam either light or heavy damage and hidden dangers, but in this heavy rain storming the role of silt. In the meantime, the phenomenon of steep slope farming in this area still exists in the survey. There is a lack of reservoirs and drainage systems in some small watersheds. Some of the soil and water conservation projects are not well managed and maintained, with low level of economic development and weak awareness of water and soil conservation. [Conclusion] The soil erosion caused by the severe storm flood was still serious, while the slight soil erosion in the grassland for returning farmland to grassland proves that soil and water conservation work is still very important in this area. In the loess plateau where the ecological environment is fragile, we should continue to step up environmental protection measures and step up soil and water conservation efforts, especially on steep slopes. At the same time, it is very necessary to professionally design and implement a small watershed water storage, diversion and drainage network system.