| The Yellow River has developed the Yellow River Delta wetland with its unique water and sediment conditions,tail swing mode and Bohai weak tide dynamic environment interaction.The evolution of the Yellow River Delta wetland is affected by the dual effects of natural factors and human factors,and the change of the Yellow River is one of the most important driving forces affecting its environmental changes.The change of the flow path in the Yellow River leads to the change of water and sediment conditions,topography,soil nutrients and salinity,and then affects the evolution of wetlands.This paper will study the influence of the Yellow River diversion and its influence on the evolution of the delta,in order to deepen the theoretical research of wetland science,the Yellow River delta wetland resources and environment evaluation system,wetland protection,wetland restoration and reconstruction,development and utilization to provide scientific support,having important practical significance and reference for sustainable development the Yellow River Delta wetland.Based on the National Natural Science Foundation of China(41371517),Shandong Province Science and Technology Program(2013GSF11706),the "3S" technology,mathematical statistics,field investigation,laboratory analysis and simulation model with the traditional combination were used in the research of the impact of the Yellow River diversion evolution of downstream river delta wetland.Based on the 158 remote sensing images,the river and shoreline data were extracted,the types of wetlands were interpreted,and the quantitative inversion was carried out with the measured data.This paper studies the evolution process of the the Yellow River since 1976,to investigate the influence of the Yellow River diversion of the Yellow River delta wetland from the shoreline and area change,wetland landscape change and wetland habitat change perspective.The main conclusions of this paper are as follows:(1)In the early stage of the Yellow River diversion,its land-making speed is the fastest in the estuary.Sandspit is rapidly extending to the sea,which is usually developed as "wedges" by "fan-shaped".The proportion of sediment to the offshore is enlarged to reduce the land-making speed.Later,the flow path begins to swing,and the land speed is accelerated again.However,the erosion of the abandoned channel area in the Yellow River will be influenced mainly by the dynamic action of the ocean.The initial erosion rate of the diversion is fast,and then the speed gradually slows down,with almost relatively stable rate erosion,the original sea into the sandspit will gradually become smaller or disappear.(2)The early stage of the Yellow River diversion,the current flow of the estuary area of its fastest land reclamation,sand mouth quickly extended to the sea,generally from the "fan-shaped" development for the "wedge",the proportion of sediment into the sea to expand,And the Yellow River abandoned the old coastal area will be eclipsed,the coastline erosion is mainly affected by the role of marine power,diversion early eclipse back fast,after the speed gradually slowed down,Will be almost at a relatively stable rate of erosion,the original into the sea will gradually become smaller or disappear.(3)The wetland landscape in the Yellow River delta is affected by natural and man-made factors,while the influence of the Yellow River swing and diversion on the front wetland of the Yellow River delta is the most significant.The spatial pattern of wetland landscape has a certain regularity,and the spatial distribution of wetland landscape is relatively concentrated.The distribution of the river is symmetrical,which is usually blocky or banded;The center of gravity of wetland landscape types changes roughly in two directions: the north and south,the east and west.The change of wetland landscape has a certain regularity,the natural wetland landscape shifts the largest,and the artificial wetland is small,the non-wetland landscape is the least.(4)The effect of the Yellow River diversion on 96 freshland wetland and 76 wetland habitat is significant.The total soil salinity of 76 wetland is obviously higher than that of 96 freshland wetland,and the biomass of 96 freshland wetland is significantly higher than that of 76 wetland.The soil salinity of the Yellow River Delta wetland is showing an overall decreasing trend from sea to land,increasing outward from both sides of the Yellow River;On the contrary,the vegetation biomass is showing the increase from the sea to the land,declining outward from both sides of the Yellow River.Since 1976,the evolution of the Yellow River channel has been dominated by man-made diversion and accompanied by the evolution of the natural swing of the frontier river.The change of the Yellow River channel affects the development of the Yellow River Delta wetland.The change of flow path not only causes the dynamic changes of shoreline and area of the Yellow River Delta,but also changes the habitat conditions such as water and sediment conditions,topography and soil salinity in wetland,and has a profound effect on the wetland evolution process of the Yellow River Delta. |
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