| The Tiaozini sandbank is located in radiation shoal margin area in Dongtai City,Jiangsu Province coastal,has long been in a deposition environment,the beach has become the land because of continuous accretion and is one of the fast sedimentation coastal zones of the whole province coastal area.It has fairly good foundation for beach reclamation and development.Jiangsu province Tiaozini reclamation area(first period)high reclamation project is located in the offshore shoal of Tiaozini sandbank,In north-south direction,it ranges from the Liangduo estuary to fangtanghe gate,and in east-west direction,it ranges from the cofferdam of reclamation area to the west side of xidagang.The post evaluation analysis of the tiaozini first period reclamation project can not only figure out the scope and extent of the impact of the project on the marine environment,but also provide suggestions for the later operation and management of the project,and can also provide reference for the follow-up of other reclamation projects.The main contents and conclusions of this paper are as follows:(1)By using the technology of GIS,remote sensing and mathematical model,through collecting the measured hydrological data,topographic data and remote sensing images of the research area in recent years,the characteristics of the hydrodynamic environment,topography,erosion,marine habitat and social economic benefits after the construction of the first phase of the reclamation project are evaluated.(2)The implementation of the first phase of tiaozini reclamation project changed the shape of the coastline,which had a certain influence on the tidal current near the project,but had little influence on the whole tidal current field of the radiation sandbar;the implementation of the reclamation project increased the water blocking effect,the velocity at the front of reclamation area was generally reduced,and the range of velocity reduction more than 0.1 m/s is less than 25km.The closer the distance to the project,the more the velocity decreases.On the whole,the influence of the implementation of the first stage reclamation project on the flow and flow velocity is limited to the east side of the project 15km and the north side of the 13km,and has little influence on the outer edge of the radiation sand bar in the outside of the tiaozini sandbanks.The flow velocity decreases obviously in the front of the engineering dike and the south of tiaozini,which is easy to cause the silt of the terrain in this area;The implementation of the first phase of tiaozini reclamation project had little influence on the tidal fluxes of the main tidal waterways in the radiation sandbar,and the total tide flux decreases slightly,the ebb tidal flux variation is greater than the tidal flux.(3)The implementation of the first phase of the reclamation project makes the sedimentation rate of the tidal flat quicker,within the 10km range of the foreland of the embankment,the deposition rate is 0.04m/a in the natural state,and the deposition rate is slightly increased in the construction period,which is 0.06m/a.The silting effect is obvious after the completion of the project construction,and the annual deposition rate has reached 0.335m/a;The sedimentation rate of the beach in the construction period is 0.138m/a,and the deposition rate reaches 0.251 m/a after the completion of the construction,which indicates that the construction of the first phase of the reclamation project has increased the overall deposition rate of the muddy tidal flat.Because the reclamation project occupied the part of the tidal channel in the XiDagang,it changed the hydrodynamic environment near the engineering area to a certain extent,and caused the swing adjustment of the XiDagang and DongDagang,which caused the obvious scour in the local area,and the tidal flat except the swinging area of the tidal gully was mainly slowly silting up.At the same time,the construction of the engineering dyke obstructed the direction of the flow of water,resulting in the decrease of flow velocity in the front of the dike,and the most obvious decrease in the flow velocity in the northeast and Southeast angles of the dike,which resulted in the continuous deposition of the tidal flat in the northeast and the southeast of the reclamation project.(4)The implementation of the first phase of tiaozini reclamation project did not change the overall trend of sediment transport in the vicinity of tiaozini sandbank,and the amount of sediment transport reduction in all directions is generally small.After the project,the erosion and siltation coexist in tiaozini sandbank,and the net input suspended sediment in the whole area is 57 thousand and 760 tons in a tidal cycle,indicating the trend of siltation in the whole area of tiaozini,in which the north and South are the net sediment input direction,the silt in the Northern and the southern area of tiaozini is obvious,the East is the sediment output direction,and the eastern area of tiaozini is slightly scoured.(5)in 2006-2012,silty sand is the main type of sediment in radiation shoal,and the surface sediments were coarsening.In 2016,the measured cross section of surface sediments showed that the sediment near the project was mainly silty sand after the implementation of the first phase of tiaozini reclamation project.The grain diameter near the levee to far 300m is relatively fine,and the outward particle size is coarse-grained,which indicates that the reclamation engineering construction makes the sediment particles in the frontier of the reclamation area refined and the outer beach surface particles coarser,which is related to the weakening of the tidal flow power to the shore,and the reclamation activities make the silt surface of the embankment frontier heighten obvious,tidal power and bottom.The friction force of the section is further strengthened,the hydrodynamic force is getting weaker and the fine particles are more easily enriched in the higher part of the beach surface.At the same time,a large amount of rice grass is introduced in the front of the embankment of the reclamation project of the mud mud,which can also play a good role in energy dissipation and promote the deposition of fine particles.(6)Natural landscape has obvious advantages in the proportion of landscape types in the area of the first phase of tiaozini reclamation project.In 2010,the natural ecological landscape(wetland,unused land,water body)accounted for 100%of the total landscape of the reclamation area,natural landscape accounted for 98.01%in 2014 and 63.7%in 2017.With the construction and development of a reclamation project,the natural landscape is gradually decreasing while the artificial landscape(construction,ditch,pond)is gradually increasing.(7)The evaluation value of the agreement degree of the first period reclamation project is 0.6938,which indicates that the first period of reclamation works well with the local industry,and the first period of tiaozini mud reclamation works on the social benefit of the region.With the further development and construction of the tiaozini mud,the social benefits of the tiaozini mud reclamation project will be further highlighted. |
PDF Full Text Request