Flood Disasters and Climate Changes During Song and Yuan Dynasties in Kaifeng Area

Flood disasters information in Northern Song Dynasty in 960-1127 and Yuan Dynasty in 1264-1367 in Kaifeng area was extracted based on historical records.By comparative study,characters of flood disasters and climate changes reflected by them during these two periods were discussed.The results showed that frequent occurrence of flood disasters during both periods in Kaifeng area,and flood disasters occurred once every 2.75 to 2.89 years in average.Precipitation pattern at grade Ⅱ was the main type in Northern Song Dynasty.The crevasse of rivers and overflow at grade Ⅲ and Ⅳ,however,turned out to be the prominent performance during Yuan Dynasty.Flood disasters occurred frequently in early 70 years of Northern Song Dynasty.Instead,they exhibited a low-incidence in earlier and later of Yuan Dynasty,but occurred high-frequently during the middle 60 years.Flood disasters during both dynasties concentrated in summer and autumn,and the precipitation increasing or concentration of summer monsoon occupied the main driving force.The spatial differences were small in Northern Song Dynasty,but had remarkable differences dependent on distances with the diversion of the Huanghe River in Yuan Dynasty.The climate during about 40 years of the earlier Northern Song Dynasty was a little dry,then,entered physic wet-dry changes.The climate in Yuan Dynasty kept wet and continued till late Yuan Dynasty.Furthermore,flood disasters during both periods had common inter-annual cycles like quasi-3 and 7 years.