After the PRC was founded, the amount of documents of flood and drought disasters
was much more than that of the historical period. Due to the improvement of the research conditions,
a variety of quantitative indicators for comprehensive evaluation and a more precise grade
division emerged. During this period, there were 7 grades for classification.
The 1st for a catastrophic flood, the 2nd for a severe flood, the 3rd for a common flood,
the 4th for common years, the 5th for a common drought, the 6th for a severe drought,
and the 7th for a catastrophic drought.
The difference between the standard of 5 grades and that of 7 grades is that
based on the former standards, the 1st grade includes both severe floods and catastrophic floods,
and the 5th grade includes both severe droughts and catastrophic droughts.
Grades and the standards for grade division of floods
Three quantitative indexes have been drawn up for the classification of flood disasters
during the 40-year period: the affected area rate (affected area/sown area),
the precipitation anomaly in summer (June to September) and recurrence period
of annual maximum peak discharge of representative station.
The 1st index indicates the loss, while the others indicate the severity
of the causes of disasters.
According to the division of the natural regions of Northeast China and the data of
the historical period, the whole northeast region has been divided into 12 districts:
Nenjiang district, the second Songhua River district, the main stream of Songhua River district,
West Liao River district, East Liao River district, the middle and lower reaches
of Liao River district, Tumen River district, Yalu River district, rivers of the Bohai sea district,
rivers of Liaodong Peninsula district, the main stream of Heilong River district
and Wusuli River district. And 11 of them are the same of those in the historical period.
Based on the indexes and the standards in the historical period, the grades of flood
and drought disasters in different districts over the 40 years have been set.
The information is provided by Disaster Risk Reduction Knowledge Service.