A STUDY ON FRACTAL STRUCTURE OF FLOOD SEQUENCE IN LUOHE RIVER BASIN IN MING DYNASTY

Based on data of historical documents, the authors have studied flood disasters in Luohe River basin between 1368 and 1644 AD. It is found that the sequence has some features. There were 56 flood disasters in Luohe River basin between 1368 and 1644 AD, approximately occurring once every 4.95 years on average. The 56 flood disasters could be classified into 4 grades, catastrophic flood, big flood, moderate flood, and low flood, and of the floods, there were three catastrophic floods, 12 big, 16 moderate and 25 low ones. The circumstance could be divided into four main periods. The first period was between 1369 and 1429 AD, with a relatively lower frequency of floods. The second period was between 1430 and 1489 AD, with a relatively higher frequency of floods. The third period was between 1490 and 1539 AD, with a relatively lower frequency of floods. The fourth period was between 1540 and 1644 AD, with a relatively higher frequency of floods. The self-similar properties of flood disasters reveal the sequence's fractal feature. It is found that the fractal dimensions of flood in different grades are all below 0.2, with the same non-scaling range between 2 and 256, which demonstrates the sequence's bias of long period and the concentration of all grades of disasters.