The division of grades is a unified index which indicates the degree of disasters and plays an important role in analysing the regional regularity of floods and droughts. The standards for grades dividing have not been unified in China at present. Considering the situations and datas of Northeast China, there are 2 periods of grades division of flood and drought disasters: the historical period (1746~1950) and the PRC was founded for 40 years (1951~1990).
The historical period from 1746 to 1950
The division for grade standards of flood and drought disasters was based on the historical documents of floods and droughts. A small amount of datas on precipitation, temperature and water level after 1990 were saved as well as some historical documents of floods and droughts. The water logging could not be told from the floods at the time.
The historical flood and drought disasters were divided into 5 grades: the first grade was for severe floods, the second grade was for common floods, the third was for normal years, the fourth grade was for common droughts and the fifth grade was for severe droughts. The division is mainly based on the common words used to describe the flood and drought disasters in the historical documents.
The first grade: severe floods
The descriptive words (or sentences): run of wet weather; a heavy rainfall lasted for several days; a storm in a sudden; a severe flood of rivers or lakes; sum less acres of land were inundated; countless casualties were caused; the losses were so serious that the tax had been exempted, etc. These phrases were used to describe a long-lasting and wide-ranging flood.
The second grade: common floods
The descriptive words (or sentences): a rainfall that lasted for several days; a storm in a sudden; rivers flooding; the water was very deep;the food in short supply, etc. These phrases were used to describe a flood caused by local rainstorms.
The third grade: common years
The descriptive words (or sentences): good weather for crops; a year of good harvest. These years turned out to be years with little loss and satisfying harvest.
The fourth grade: common droughts
The descriptive words (or sentences): lack of rainfall, river ran dry; droughts of a month or a season; postponement of taxation, etc. These phrases were used to describe a drought causing relatively less loss.
The fifth grade: severe droughts
The descriptive words (or sentences): droughts lasting for several years; droughts lasting for spring and summer; no rainfall for several months; the weather was scorching and hot; a severe disaster; harvest little or even no harvest at all; the government distributed foods to relive people from the disaster and the tax of crops had been exempted, etc. These phrases were used to describe a severe, long-lasting and wide-ranging drought.
According to the regional distribution of documents, the entire northeast region is divided into 11 districts by the rivers, and the representative points were as follows: Nenjiang (Qigihar, Nenjiang), second Songhua River (Peter lane, Jilin, Changchun), Songhua River (Harbin, Jiamusi, three name, Hulan, hulalin) Xiliao, (Chifeng, Tongliao), East (Liaoyuan, Gongzhuling), the middle and lower reaches of Liaohe River (Kaiyuan, Shenyang, Tieling), Tumen River (Hunchun), the Yalu River (Dandong, Ji'an), the rivers west of Bohai (Chaoyang, Jinzhou), the Liaodong Peninsula (Dalian, Niu zhuang) Heilongjiang River(Ai Hun).
In addition, on the basis of the previous grade division, the flood and drought grades of Songhua River and Liao River basins have been completely determined. The grade of Songhua River is based on the grades of the main steam of Songhua River, the second steam of Songhua River and Nen River. The grade of Liao River is based on the grades of the middle, lower reaches of Liaohe River (including HunTai river basin), West Liao River and East Liao River. The flood and drought grade of Northeast China is based on the grades of the basins of Songhua River, Liao River and other rivers.
The information is provided by Disaster Risk Reduction Knowledge Service.
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