Causation Analyses of High Water Level in the East Part of the Yangtze River and Its Services of Forecasting Decisions
The high water level is one of the flood disasters found frequently in the east part of the Yangtze River.Aimed to high water level days in the latest 13 years,the causes for high water level and the main factors are analyzed using the hydrologic data and synoptic chart on the basis of synoptic theory,the lunar tide theory and the storm tide theory etc.The results are as follows:(1)The high water level in the east of Yangtze River happens during the peak periods of the lunar tide and is directly affected by the high tide level.(2)Typhoon and west wind trough are the weather systems leading to the high water level.(3)The flood from the upstream Changjiang River induced by the west wind trough discharges eastwards passing the east part of the river;the solitary wave forced by the typhoon near the continental shelf makes the sea surface rise severely,and the back-flows of the storm surge intrudes the east part of the river.(4)There is no significant relationship between the high water level and the local precipitation.