1, overflow pinyin: m?ny?.

2, the meaning of overflow: too much and overflow. Filling; Rich.

Overflow refers to the complete outflow of water. Overflow also refers to the fact that the actual flood level exceeds the elevation of the existing dike top, or the wind and waves overturn the dike top and the flood overflows into the dike. Li Daoyuan of the Northern Wei Dynasty wrote in "Notes on Shui Jing Bao Qiu Shui": "The flood broke out, damaging three quarters, leaving more than 70 feet on the north bank and flooding the canals." ?

Xiao Ting's Miscellaneous Notes on Seeking Fengshen in Qing Dynasty: "I heard later that Assistant Minister Mo looked at Jinyun. This is a golden dam, which once overflowed in the middle of Kangxi. It took decades to complete, but not so fast. " Chapter 12 of Kang Zhuo's "Dongfanghong": "The flood passed the foot of Hanlongtai Banpo, overflowed into the low-lying land in the south and west of the village, and accumulated into puddles."

Under normal circumstances, the earth embankment is not allowed to cross the water. Once there is a great danger of overflow, it will soon cause the dike to burst. Therefore, emergency measures should be taken to prevent overflow in flood season. 1998 During the flood season, many dikes in the Yangtze River, Nenjiang River and Songhua River basins were in great danger that the flood level exceeded the crest elevation, so it was not allowed to build sub-weirs urgently and rely on them to retain water.

Main reasons:

1. The actual flood exceeds the river design standard. Design standards are generally accurate and authoritative, but due to insufficient hydrological data and representativeness or cognitive reasons, they may be set on the low side, which may lead to overflow.

2. The dam itself does not meet the design standards. This may be due to insufficient investment, the top of the dike did not reach the design elevation, or it may be due to the unstable foundation, false tamping and excessive settlement, which made the top elevation of the dike lower than the design value.

3. The siltation of the river course is serious, and the cross section of the flood passage is reduced, which props up the upstream and makes the flood level of the silted river reach and its upstream rise.

4. Because of man-made buildings blocking water or blindly reclaiming land on the river, the cross section of the flood is reduced, and planting on the river beach increases the roughness, which affects the flood discharge capacity and raises the flood level.

5. The breakwater wall is not high enough, and the waves cross the top of the breakwater.