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.