Flood disaster has always been one of the severe natural disasters in Northeast China, and it is juxtaposed with drought disaster as two main natural disasters. Flood disaster is caused by the excessive amount of water and the movement or the form of existence which can do harm to human's society under some environmental conditions. The flood disasters include rainstorms, snow-melting flooding, mudslides, storm surges, soil salinization, and snow disasters, etc, among which the rainstorm disaster is the most frequent and most loss. In the historical document, people had used "rain", "heavy rain" and "lao" "liao" to describe flood disasters.By 20th century, meteorological and hydrological observation had developed, and people started to use "rain condition", "water condition" and "disaster condition" these 3 quantitative indicators to describe flood disaster.
The flood disaster records in Northeast China can be divided into two sections, the two periods: before and after the founding of the People's Republic of China. Generally speaking, the data record in the previous period is simple, the temporal and spatial distribution characteristics of the disaster are not prominent, the disaster situation is not complete, and all types of flood disasters are simply called floods. The rainfall, flood and disaster data in the latter period are relatively sufficient, and it has the basis for compiling flood classification.
According to the causes, floods can be divided into five kinds.
(1) Storm flood: flood caused by heavy rain and rainstorm.
(2) Snowmelt flood: the temperature or rainfall causes the snow on moutains to melt, forming a flood.
(3) Glacier flood: a flood caused by melting glaciers as a result of rising temperatures.
(4) Ice flood: the ice in the riverway breaks the dam, forming a flood
(5) Dam-break flood
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