Research On The Change Of Erosion And Siltation In The Coastal Zone And Threshold Of Water And Sediment Of Yellow River Delta Based On Remote Sensing

The Yellow River Delta is one of the key areas for the development,management and protection of the Yellow River basin,and is also an important part of maintaining the Yellow River's healthy life.Influenced by climate change and human activities,the water and sediment flux which from the Yellow River to sea has changed dramatically since the second half of last century,the water inflow and incoming sediment in the Yellow River Delta tend to decrease.As a transition zone between land and sea material and energy exchange,the erosion and siltation in the coastal zone of the Yellow River Delta has undergone a complex response process,and the ecological security of the Yellow River estuary area is facing a severe challenge.In this paper,the water and sediment data of Lijin station and the remote sensing image data of the Yellow River Delta are used to systematically analyze the characteristics of the change of water and sediment which from the Yellow River to sea and the dynamic evolution law of erosion and siltation in estuarine coastal zone.The response relation between the process of erosion and siltation in estuarine coastal zone and water and sediment carried into the sea is explored.The critical water and sediment threshold value to maintain the balance of the erosion and siltation in the Yellow River Delta and the relation of comprehensive critical water and sediment conditions are put forward.It provides a reference for river management and coastline protection in the Yellow River Delta.The main contents and achievements of this paper are summarized as follows:?1?The study on the evolution law of water and sediment in Lijin station found that annual runoff sediment discharge showed a decreasing trend from 1950 to 2015 and it has the characteristics of rich and dry alternation and significant periodic variation on the interannual,such as,annual runoff and sediment discharge have 30 and 18 years of main cycle respectively.The distribution of water and sediment showed obvious seasonal differences and mainly concentrated in the flood season?7-10 months?,and since the regulation of water-sediment,the average runoff in flood season decreased about 1.8 times,the average sediment transport decreased about 6.4 times.?2?According to the interpretation results of remote sensing image in the Yellow River Delta area,the characteristics of erosion and siltation in the coastal zone are analyzed.The results showed that over the past 1976²010 years,the land area of flow path of Diaokou river has decreased from 332.4km² to 192km²,and the annual erosion rate is 4.01 km²yr^-1.Influenced by ecological replenishment in the Yellow River Delta,the coastline erosion of flow path of Diaokou river are effectively controlled and the silt erosion is basically balanced after2010.Since the diversion of flow path of the Yellow River into the sea in 1976,the flow path of Qingshuigou has experienced four stages:rapid sedimentation period,stable period,rapid erosion period and erosion deposition alternating period.The land area increased by 300km²and the average deposition rate was 7.56 km²yr^-1.?3?The response relation between the process of erosion and siltation in estuarine coastal zone and water and sediment carried into the sea shows that when the runoff is 10.54 billion m3yr-1and the sediment discharge is 176 million tyr^-1,or the water and sediment conditions meet the relationship:0.027Q+4.699Qs=8.261,the erosion and silting process of the Yellow River estuary coastal zone is in a critical equilibrium state.