长江中游河道崩岸预警技术及其初步应用

Early-warning technology of bank erosion and its preliminary application in the Middle Yangtze River

近年来由于上游来水来沙变化及水库运用等影响,长江中游河床剧烈冲刷,崩岸现象频繁,增大了河道防洪压力,但中游崩岸监测预警系统尚未完全建立。结合崩岸过程预测与崩岸预警等级划分,提出了长江中游河道崩岸预警技术。在崩岸过程预测中,首先通过预警河段的河势情况,确定崩岸易发区;其次,耦合基于随机森林模型的崩岸概率计算与基于动力学模型的崩岸过程模拟,对崩岸易发区的崩岸强度进行评估;随后,计算了由堤外滩地宽度及临江住房面积构成的崩岸危害程度指标;最后,通过对各指标数据进行融合,划分崩岸预警等级(Ⅰ~Ⅲ级)。该技术被初步应用于长江中游下荆江河段2020年的崩岸预警。

Under the impacts of the operations of upstream cascade reservoirs, the river channel in the Middle Yangtze River has suffered from intensive erosion, resulting in a frequent occurrence of bank erosion event that threatens the safety of riparian levees. However, the monitoring and early-warning system of bank erosion is not well constructed in the MYR. Therefore, this study proposed an early-warning technology of bank erosion event, which combines a bank erosion prediction module with a warning-level grading module. In the prediction of bank erosion, potential bank erosion sites are firstly selected relying on a prior assessment of the river regime. The occurrence probabilities of bank erosion are then calculated by a well-trained Random Forest Model for bank erosion, and the erosion widths at these sites are calculated by a dynamic model. In terms of the grading of warning-level, two additional indicators of floodplain width(between the water and the levee) and riparian residential area are adopted to represent the importance of a selected site to the riparian society. A warning-level matrix is constructed to combine these four different indicators into a final warning-level of bank erosion. The proposed technology is used to conduct the early-warning process of bank erosion event of the Lower Jingjiang Reach of the MYR in 2020.