关键词: 黄河下游, 决口改道, 人类活动影响, 淤积

Abstract: It is well known that the Yellow River is a very famous river with much sediment in the world. Deposition of the river bed as well as the breach and diversion of the river course happened frequently through the whole historical period, so that the accumulation of North China Plain has been getting more faster since Quaternary period. According to field investigations, the behavior of the lower Yellow River before Tongwaxiang breach happened was basically the same as that of the modern lower Yellow River. The average accumulating ratio of the lower Yellow River for the riverbed was 6 5 cm/a during 1855~1982, not including 1938~1947 when the Yellow River took the southern course and 7 7 cm/a for the floodplain.\;It is shown from statistical data that the frequency of river breach and diversion in the Lower Yellow River has been faster. The frequency of river breach and diversion in the Lower Yellow River wasn’t very high before the period from 602 B C to A D 907, but increased more obviously during Wudai Dynasty to Song and Yuan Dynasty than before, almost one time of breach per two years. In order to guarantee water transport of grain to the capital during Ming Dynasty, the northern levee was reinforced, but the southern one was not, so that the breach frequency of this period was doubled compard with Song and Yuan Dynasty. On average, there are three times of breaches per two years during Qing Dynasty to Republic of China.\;The accelerated deposition and the increasing frequency of breach and diversion in the Lower Yellow River are caused by the complex action of natural factors and human activities. With the increase of population, the change of cultivation types and the destroying of vegetation in the drainage area of the Middle Yellow River during the historical period, soil erosion was greatly intensified and the oncoming sediment to the Lower Yellow River increased, so that deposition, breach and diversion happened frequently in the lower Yellow River.

Key words: Breach and diversion, Deposition, Effect of human activities, The Lower Yellow River