长江中下游平原湖区涝灾极为严重。以洞庭湖腹地大通湖垸为例，基于平面二维水流数学模型，采用有限体积法和非结构网格，研究该区域在不同外洪条件与不同降雨组合条件下的沥涝情况，得出了区域内涝灾分布情况及致涝率，并定量计算分析了外洪水位变化对内涝造成的不利影响。模型计算结果可为涝灾预测与评估提供技术支持。

Waterlogging in the middle and lower reaches of the Yangtze River is very severe. In the paper, on the basis of the two-dimensional flow model and by applying the finite volume method and unstructured mesh, the waterlogging and drainage of the Datong Lake-polder with different precipitations and floods were studied. The spatial distribution of waterlogging in the Lake-polder area and the ratio of waterlogging were gained. The negative influence of the floods on the waterlogging was analyzed quantitatively. The model results can provide technological support for the waterlogging forecasting and assessment.