Lower Weihe River The Historical Periods Floods Impact Of Socio-economic Development

The natural disaster is an incident that runs through the whole history of earth, which exists in everywhere and every moment. China is a country with the highest frequency of flood disasters in the world. From the past history, flood disasters have arisen for many times.During the period of about 2000 years, the area in the lower reaches of Weihe River was once the center of Chinese nation, and even the political, cultural and economic center throughout the world. As the land of imperial seal, the area of the lower reaches of Weihe River was rich in historical records. Meanwhile, under the current situation of global climate change, knowing about the effect of flood disasters occurred in the lower reaches of Weihe River on social and economic development in historical period, which had theoretical and practical significance for flood prevention and disaster reduction in the future. Therefore, by using the methods of historical documentary combined with field survey, chart and map display, and so on, and also by means of the abundant and accurate literature records of flood disasters, a study was made on the frequency, time series, spatial distribution regularity of flood disasters, and its effects on social and economic development, then discussed the reason that maybe caused the flood disasters and finally made some suggestions to flood prevention and disaster reduction in the lower reaches of Weihe River from 308 B.C. to 1949 A.D.. The main results were as follows:1. According to the grade series, during the two periods that from Tang Dynasty to Ming Dynasty and from Qing Dynasty to the Republic of China 1949, flood disasters were graded in the lower reaches of Weihe River year by year, It is found that:From 618 to 1644, in the lower reaches of Weihe River, flood frequency at the second grade was the highest, and then the first grade; the frequencies of flood disasters at the third and the fourth grade were lower.From 1644 to 1949, in the lower reaches of Weihe River, flood frequency at the second grade was the highest, and then the first and third grade; the frequency of flood disasters at the fourth grade was lowest. 2. According to the frequency of flood disasters in every centuries and varying regularity, the evolution process of flood disasters in the lower reaches of Weihe River from 308 B.C. to 1949 A.D. can be divided into three periods:The less floods period:from the 4th century B.C. to the 6th century A.D., disasters were rarely recorded, and the occurrence cycle of disasters was also not obvious. The fluctuating period:during the 7th-13th century A.D., from the 7th century A.D. to the 8th century A.D., the number of disaster increased; from the 8th century A.D. to the 13th century A.D., the number reduced constantly rather than before.The more floods period:From the 14th century A.D. to the first half of 20th century A.D., the number of recorded disasters increased substantially.3. The seasonal regularity of flood disasters in the lower reaches of Weihe River in historical period:According to the seasonal statistics of flood disasters in the lower reaches of Weihe River from 308 B.C. to 1949 A.D., It was concluded that:during the period, the floods in the lower reaches of Weihe River mainly occurred in summer and autumn; and then spring floods and summer and autumn floods; spring and summer floods had lower incidence; the incidence of winter floods and spring and summer and autumn floods was lowest.From the statistics of each county in the lower reaches of Weihe River where floods happened, it is discovered that the disasters were mainly occurred in summer, and then in autumn; spring floods and summer and autumn floods had. lower incidence. There were some counties that frequently occurred floods in summer, including Huayin city, Hua County and Dali County. Floods occurred frequently in autumn was Hua County.4. The spatial distribution regularity of flood disasters in the lower reaches of Weihe River in historical period:From the sketch map of the lower reaches of Weihe River:the counties with more flood disasters were Huayin and Hua county located in the both banks of Weihe River flowing into Yellow River and Dali county located in the both banks of Weihe River flowing into branch of Yellow River-Luohe River; and then the counties located in the both banks of the mainstream of Weihe River; the counties that was far from Weihe River were less affected by flood disasters.5. The effects of flood disasters in the lower reaches of Weihe River on social and economic development in historical period are shown as follows:The effects on agricultural production:The crops were damaged directly and the farmlands were inundated by flood disasters, the destruction of the second floods to crops and farmland was smaller, but all farmlands could be flooded by the third disasters and the fourth disasters, and the areas of farmland sharply increased as well.The effects on the people's life:The flood disasters at the third grade and the fourth grade can cause directly a large amount of deaths, and the death toll also can be increased because of the famine that is secondary disaster caused by flood disasters; the plague caused by flood disasters and famine pose a threat to the people's life and health status again, even leads to death.The effects on social economy:Flood disasters in the lower reaches of Weihe River in historical period make labor force reduce greatly, which will undoubtedly affect the speed of the local economic development. Meanwhile, the agricultural economy becomes worse because of land which has fallen out of cultivation. However, the immigrants suffered from disasters not only can relieve the relief pressure of the stricken areas, but also can offer the sufficient workforce to moving into the area for land exploitation and economic development:The effects on social stability:the crops damaged and farmlands flooded by flood disasters make the crop yield decrease, and cause the famine, which is a very important factor that bring about the social instability in history.The effects on selecting capital site and moving the capital to another place:The flood disasters caused by climatic change often cause failure of crops, war and nation migration; the serious floods will also destroy buildings and cities, and affecting the development of city and people's life.6. The main reasons of flood disasters in the lower reaches of Weihe River in historical period include climate, natural and human factors.Flood disasters always occurred frequently during the period of low temperature and climate fluctuating. The topography of the lower reaches of Weihe River is complicated, which is an significant factor for the formation of rainstorm. The main reasons for floods are the uneven distribution of monthly precipitation and large inter-annual variability in the Weihe River. Human being's blind reclamation and deforestation also bring about the ecosystem unbalance, serious soil erosion, and floods happen frequently.7. The following is some measures for flood prevention and disaster reduction in the lower reaches of Weihe River in historical period:The construction of water project is precondition to control flood damage. Therefore, it is the most important thing for flood prevention and disaster reduction to build irrigation projects.