Morphologic Characteristics Of Tidal Creeks And Catchment Area In The Central Jiangsu Coast Using LiDAR DEM

The resources of the tidal flats in the central Jiangsu coast are abundant,and there is great potential for the development and utilization of marine resources.The tidal creeks on the tidal flats are dense-distributed and well-developed and the central Jiangsu coast is considered as an ideal area for studying the morphological characteristics of tidal creeks.Under the effect of hydrodynamic environment and human activities,tidal creek networks are sensitive and frequently changing.However,the rapid evolution of tidal creeks poses a certain threat to coastal engineering such as reclamation and construction of ports.The research on the morphological characteristics of the tidal creeks in the central Jiangsu coast provides a scientific basis for the protection of coastal engineering.In this study,the tidal flats in central Jiangsu coast was taken as the study area.Based on LiDAR DEM data,the morphological characteristics of typical tidal networks were analyzed with the support of remote sensing technology and GIS technology.The characteristics of distribution and evolution along the coast,the radial sandbanks and the tidal zone were analyzed respectively.The main contents of the study include:(1)The tidal flats were divided to analyze the zonality of morphological characteristics of tidal creeks using HJ-1A/B satellite images.The definitions and calculation formulas of the nine morphological characteristics(including level,length,width,depth,width-depth ratio,density,bifurcate ratio,curvature,and unchanneled length)of tidal creeks and catchment area were described.(2)The index of morphological characteristics of selected typical tidal creek networks along the coast and within the SYSRSR(South Yellow Sea Radial Sand Ridges)were calculated using LiDAR DEM data.The relationship between level versus length,width and depth were analyzed,respectively.In addition,the morphological characteristics of tidal creeks within each sandbank and seaward/shoreward side were constracted,and the reasons for the difference were discussed.(3)According to the calculation,the zonality of morphological charateristics of cathment area along the coast and different side of radial sandbanks were analyzed respectively.Moreover,the fitting analysis between these characteristic parameter were conducted.The results indicate that:(1)The tidal creeks are concentrated in the estuaries within the coastal tidal flats and are well-developed with level up to 6,while tidal creeks within the SYSRSR are concentrated in the Dongsha sandbank with level up to 5.Many small tidal creeks with level 1 or 2 develop within the SYSRSR.(2)Through the division of tidal flat blocks and the statistics of the morphological characteristics of typical tidal creeks,it was found that the morphological characteristics of tidal creeks show significant partitioning and level differences:the length and width of tidal creeks near the coastal Jianggang are smaller and the depth is larger.The tidal creeks in the central part of the radial sandbanks are mostly narrow and deep,and both ends are wide and shallow.The difference in morphological characteristics is mainly related to the tidal range.The level difference of the morphological characteristics of tidal creeks is that,from level 1 tidal creek to superlative tidal creek,its length and width both increase,and the depth first increases and then decreases,usually the sub-high-grade tidal creek is the deepest in a tidal creek system,and the width-depth ratio increases exponentially.(3)Through the division of the tidal zone and the statistics of the morphological characteristics of the typical tidal catchment area,it was found that the morphological characteristics of the catchment area show significant partitioning and zonality.The density and the bifurcate rate of the coastal tidal creek catchment area from Wanggangkou Port to Chuandong Estuary are both maximal.Taking the Jianggang as the boundary,the northern tidal flat has a large curvature and the southern part has a small curvature.The density,bifurcate rate,and curvature of the tidal creek catchment area in the radial sandbanks all show that large in the middle(the Dongsha sandbank and the Gaoni-Zhugensha sandbank)and small at both ends(the Liangyuesha sandbank and the Tiaozini sandbank),but the drainage efficiency of the Liangyuesha and Tiaozini sandbanks is higher.Tidal creeks develop densely in both saltmarsh zone and mid-tidal zone,and the density and the bifurcate rate are both higher in these zones.In contrast,the bifurcate rate of tidal creeks on the seaward side of the sandbanks are higher in the low-tide zone.The tidal creeks in high-tidal and mid-tidal zones are more curved while in low-tidal zone are more straight.