The main reason of the flooding in the northeast area of China is rainstorm. The size of flooding caused by the rainstorm mainly depends on the strength, lasting time, allocation of duration, central location, central trend and coverage of rainstorm. Therefore, the floodings in different places have different characters.
The seasonal distribution of flooding is related to the seasonal distribution of rainstorm, that is to say, the season of heavy rain concentration is also a time of flood, and from the table we could find that:
The majority of rivers in the northeast area have flood between June and September, and this period was called flood season. There are also some rivers in some years had its maximum flooding in May or October, but the magnitude is not too big to cause a flooding disasters. Hovever, in the downstream of some great river, for example, Songhua River, it has its maximum flooding in October because of the large water-collecting area and the long concentration time.
July and August is the fastigium of flood, most rivers in the northeast of China have more than 80% of their annual flood in this period, especially in the area of Liao River, more than 90%. So, the major flood period in the northeast is July and August.
The rivers in the north have more numbers of floods than other rivers in the northeast area in September, such as Nen River and the downstream of Songhua River. There are two reasons, one is that the typhoon which is the main weather system of this area always be late; another is that the collecting movement of the flooding came from thousands of square kilometers of great rivers last a very long time so that the flood peaks always appear behind the rainstorm about 10-20 days. Because of these two points, the floods in September are more than the floods in July and Augusts and even sometimes the flood season will be put off to October.
The rivers in the northwest high cold region of the northeast of China were mainly influenced by the ice flood, such as Eergunai River, Hailaer River, the maximum flood always appear in the April and May.
There are some statistics about the top five maximum floods’ appearing time of representative stations in each river. And from this table, we can find that the great flood in the northeast area always took place between the late of July and the late of August, in some great rivers may be postponed to the early of September like the downstream of Nen River and Songhua River, and in the cold high area like Hailar River may arise in April and May.
The information is provided from Disaster Risk Reduction Knowledge Service.
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