Research Of Modern Sediment Transport Model Of Changhua River Estuary In Hainan Province

Changhua river is the second largest river in Hainan Province.A wave-dominated delta is developing at the estuary.On the north side of the estuary is bedrock coast,and on the south side is sandy coast.A series of spits is developing in the front of the Delta in the south,and sedimentary geomorphology of alternating sand bar and lagoon which is the unique characteristics of the wavedominated delta is developing in the back of the spits.In this paper,we use the grain size distribution characteristics of the sediments on the surface of the seafloor outside estuary and the evolution of spits to research the modern sediment transport model of the Changhua River Estuary.In order to obtain the characteristics of grain size distribution in the area,the grain size of the sediments on the surface of the seafloor outside Changhua River estuary was measured which is combined with topographic data,we can research the main factors affecting the grain size distribution of sediments.Based on the Landsat satellite and Google Earth remote sensing images from 1972 to 2021,the edge detection method is used to extract the water line,which is used as the coastline.Combined with visual interpretation,we will discuss the evolution process of spit and propose an evolution model of spit.This paper is of great significance to the study of the formation process of estuarine delta and coastal geomorphology.The results and conclusions are as follows:(1)Changhua River has obvious variation characteristics in flood and dry seasons.During the flood season,the river carries more sediment,most of which migrate to the south of the estuary,forming underwater bank slope and a series of spits,until the sea outside Sigeng spit.In dry season,the river carries less sediment,and the wave and coastal current transport the sediment in the estuary again,which promotes the extension of the spit.(2)The grain size characteristics of the sediments on the surface of the seafloor outside Changhua River estuary are as follows: gradually coarsening from northwest to Southeast and fining again in the Deep South.The characteristics is closely related to the topography.The water depth is from shallow to deep,and the grain size is from coarse to fine.The migration trend is as follows: the sediments in the northwest move eastward,the sediments in the Northeast move westward,the sediments in the middle move southward,the sediments in the southwest have no obvious trend,and the sediments in the southeast move northward.Based on the provenance,hydrodynamic and grain size characteristics,the study area can be divided into three sedimentary environments: The North deep-water fine-grained area;The Middle south uplift mixed area;The Southwest Shallow water coarse-grain area.(3)The evolution of the spit in the south of Changhua River estuary can be divided into four stages: Bending to the coast,Cracked and approach the shore,Transforming,Forming a lagoon.Based on this,an evolution model of spit is put forward,and it is speculated that there will be a sand bar lagoon alternate sedimentary landform in the future;The evolution of Sigeng spit,which is far away from the estuary,can be divided into four stages too: Bending to the coast,Cracked and approach the shore,Transforming,Merge to land.