新水沙情势下长江中下游干流岸线保护研究——以扬中市2017年江堤崩岸治理为例

River bank protection of middle and lower reaches of Yangtze River under new flow and sediment condition: case of levee collapse in Yangzhong City in 2017

近十几年来随着水沙情势的显著变化,长江中下游干流崩岸险情频发,加强崩岸治理和岸线保护是沿江防洪安全和经济发展的重要保障。在梳理三峡水库蓄水以来坝下游水沙情势变化、河道冲刷和崩岸情况的基础上,以2017年11月江苏省扬中市江堤崩岸为例,分析崩岸段近期河道演变特征和地勘资料,认为河槽持续冲刷下切贴岸及二元土质结构河岸是崩塌的主要原因,而2016~2017年连续大洪水加了快崩岸的发生。崩岸发生后立即实施了窝塘抢护并修筑临时挡水子堤,随后实施完成干堤复建和窝塘上下游岸线守护工程,实现了2018年成功度汛。此次崩岸的特点和原因在长江中下游较为典型,对崩岸治理与岸线保护具有启示作用。

Because of the river flow and sediment changing in the recent decade, the frequency of bank collapse in the middle and lower reaches of the Yangtze River showed an increasing trend. Enhancing bank collapse regulation and protection is a safety insurance of flood control and economic development along the river. The downstream river flow and sediment changing, channel erosion and bank collapse since the impoundment of Three Gorges Project are analyzed firstly. Taking the levee collapse in Yangzhong City in 2017 as an example, the recent river evolution and the geological survey data were analyzed and it was concluded that the main cause of bank collapse were the channel bank scouring and foot cutting and dualistic soil structure, and the bank scouring and cutting were accelerated by extra large floods in 2016 and 2017. The collapsed pit protection and temporary retaining sub-levee were built immediately. Afterwards, the main levee rebuilding and the upstream and downstream protecting works for collapsed pit were completed before 2018 flood season. The characteristics and causes of the bank collapse are typical in the middle and lower reaches and the treatment has significant implication for bank protection.