Ice flood mainly occurred in the Yellow River, Songhua River and some other northern rivers. When the temperature rises and rivers melt, water in upstream in low latitudes unfreeze first while water of downstream in high latitudes is still frozen because some rivers flow from low latitudes to high latitudes. The upper and ice accumulate on the downstream river bed, forming ice dam and causing disasters easily. Besides, ice floods can also occur when rivers freeze.
According to the causes of floods, ice floods can be divided into three types: ice plug flood, ice dam flood and ice melting flood. (1) Ice plug floods. After the river is frozen, the ice and crushed ice under the ice cover accumulate and block part of the water cross section, causing the water level in the upper reaches to be significantly higher. When the ice plug melts, the water is discharged to form a flood. (2) Ice dam flooding. The ice dam generally occurs during the opening of the river. A large amount of drifting ice is blocked in the river channel. The ice blocks are crawled up and down, and piled up into dam-shaped ice bodies across the section. The water section is severely blocked, so that the upstream water level of the dam is significantly higher. When the ice dam suddenly broke down, the original ice storage and trough storage capacity quickly vented, forming Lingfeng to evolve downstream. (3) Melting ice flood. The frozen rivers or river sections are mainly caused by thermal effects, so that the ice sheets are gradually melted, and the rivers are slowly drained to form floods.
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