嫩江下游洪水演进及对洪泛区植被影响分析

为揭示嫩江下游洪水演进规律及对洪泛区植被的影响,利用MIKE FLOOD建立了嫩江江桥—大赉河段的一、二维水动力耦合模型,选取1998年与2013年汛期实测资料对河段糙率进行了率定与验证,并模拟了典型河段4种不同重现期洪水的演进过程。在此基础上基于2000—2019年MODIS卫星的MOD13Q1数据集,获取了不同洪水频率淹没范围内的植被指数(NDVI、EVI),评估了嫩江下游不同重现期洪水扰动对植被的影响。结果表明:模型在率定期与验证期的模拟效果符合甲级预报精度,模型模拟精度较高;不同重现期内的植被指数具有较强的季节变化规律,且洪水对植被具有明显的破坏作用,但这种破坏作用在嫩江流域周期性相对较短,表明该地区植被的可恢复性较强;同时受洪水频繁淹没程度影响,不同重现期的植被指数符合中度干扰假说。

Analysis of flood evolution in lower reaches of Nenjiang River and its impact on vegetation in floodplain

In order to reveal the law of flood evolution in the lower reaches of Nenjiang River and its impact on the vegetation in the floodplain, a one and two-dimensional hydrodynamic coupling model from Jiangqiao to Dalai river section was established using MIKE FLOOD. The measured data during the flood seasons of 1998 and 2013 were selected to calibrate and verify the roughness of the river section, and the flood process in typical river section with four different return periods were simulated. Based on the MOD13Q1 data set of the MODIS satellite from 2000 to 2019, the vegetation indices(NDVI, EVI)of the submerged range of different flood frequencies were obtained, and the impact of flood disturbances in the lower reaches of Nenjiang River in different return periods on vegetation was evaluated. The results show that the simulation effect of the model during the calibration and verification period meets the accuracy of Class A prediction, and the simulation accuracy of the model is high. The vegetation index in different return periods has a strong seasonal variation, and floods have obvious destructive effects on vegetation. The destructive effect has a relatively short periodicity in Nenjiang River Basin, indicating that the vegetation in this area is highly recoverable. At the same time, affected by the degree of frequent flooding, the vegetation index of different return periods conforms to the moderate interference hypothesis.