Abstract: The downstream of the Funiu River was flooded frequently by rainfall and the backwater of the Yangtze River flood. In order to assess the effect of the midstream and downstream controlling flood in the Funiu River, and analyze potential submerged risk of coastal engineering structures in rainstorm period, the study simulated water depth and submerged area of midstream and downstream in different rainstorm return period by using MIKE11. The results showed that average water depth was 4.9 meters in midstream under the rainfall of 50-year return period. And the submerged area was 40 542 square meters. While under the rainfall of 100-year return period, the average water depth became 5.7 meter and the submerged area became 41 980 square meters. Meanwhile, the rainstorm would inundate the residential land at Aoshan integrated market. Besides, farmland would be submerged which located in steady slope by river bank. Under the backwater of the Yangtze River flood, water depth was 7.5 meter and flooded area was 9 890 square meters in downstream on once fifty years backwater. The two values were 8.9 meter and 10931 square meters at the 100-year return level of backwater. Moreover, residential buildings and wastewater treatment plant would not be affected. However, considered the Yangtze River flood season happened to wet period of the Funiu River, it's necessary to combine the influence of rainstorm and the Yangtze River backwater. The specific numbers were 9.4 meter for average water depth and 14 559 square meters for submerged area at the 50-year return period. And there were 10.1 meter and 16 987 square meters at the 100-year return period. What's more, under the both influence of rainstorm and the Yangtze River backwater, the wastewater treatment plant and some residential buildings would be drowned in downstream. These provided references of flood control planning and coastal engineering construction in the Funiu River. For midstream, flood control levees should be constructed, especially in flat river bank. When making flood prevention plan, it would be better to improve flood control standard for the safety of construction projects. On the other hand, the basement and side slope should be strengthened in downstream residential buildings, road as well. In addition, the wastewater treatment plant should be protected by bulwark or relocated.

Key words: numerical simulation, storm-flood impact, mountainous urban river