Geomorphical Characteristics In The Bordering Coastal Area Between Shanghai And Jiangsu Provinces And Their Significance In Sea-Area Division

Sea-area division is an important step to strengthening sea-area comprehensive management,performing sea-area use efficiently,developing ocean economy and keeping coastland in stability and solidarity.Through the study of geomorphical characteristics in the bordering coastal area between Shanghai and Jiangsu province, the paper provides technical results for deciding sea-area borderline of Shanghai and Jiangsu province.According to actually surveyed depths data,the paper provides fine depth chart to analyze seafloor character terrains,depth contours and terrain profile analysis.The paper classes the terrain of survey area to shallow beach zone,alluvia zone,channel zone and shallow sea zone.Comparing actually surveyed depths and chart depths,the paper makes erosion comparisons conclusion that Guyuansha spreads southern and northern,littoral zone of Chongming seacoast is filling up and littoral zone of Qidong seacoast is little erosion.Synthesis analysis of geomorphical characteristics,forms,structures,causes,tiny physiognomy combination and modern dynamical physiognomy course,according to geomorphical causes-form classified principle,the paper provides a geomorphical class and geomorphologic map.Third class physiognomy of survey area land geomorphic gives priority to alluvial plain geomorphic.Third class physiognomy of seashore geomorphic gives priority to manpower reconstructive coastland forms, sea-land interaction tideland forms and underwater delta forms.Classes Seabed forms with river-estuary bar,erode channel,sand waves and sand ridges.Sediment of the survey area gives priority to fine sand and clay fine sand and there are sandy fine sand and fine sandy clay.Not only erosion channel,but tideway ridges and sand forms are grown outside erosion channel.Analyzing sediment samples with laser particle analyzer,it provides that in the middle of survey area sediments are relatively thick,mostly fine sand,sorting well,majority frequency are almost symmetry form narrow peak curve.Around the survey area sediments are relatively thin,mostly clay fine sand,sorting badly,majority frequency is almost Positive skewness wide peak and middle peak curves.Sediment classes and average particle isoline tend towards NW-SE and same to seafloor terrain.Based on the field data measured,the paper provides Quasi-harmonic analysis, gets constants,calculates ellipse elements of every tidal component,calculates the properties of tidal current and identify current conditions in the survey area as not regular semidiurnal tidal current mostly,calculate maximum probable current velocities,maximum probable transport distance,the residual current velocity.Based on the field data measured,plane distribution shows a decreased variety from Changjiang north branch mouth to outside and increased along with depth.Sediment content changes with tide,and the variety range is different with sites and layers, Surface layers variety is smaller than bottom layers,the variety of west side Guyuansha is bigger than east side,and in every site sediment variety course are same with corresponding current velocity hydrograph.Aimed at concern question of sea-area division,based on erosion and deposition evolution background in the whole survey area,emphatically discussed erosion and deposition evolution characteristic of Guyuansha,combined tide flow,sediment data, seabed characteristic,analyzed erosion and deposition evolution mechanism,the paper got a conclusion that Changjiang north branch will keep filling up,finally trends to die out,Chongming island will move northward and combine with land.At last the paper provides a reasonable division plan that just considering geomorphical conditions and coast evolution,taking middle line of south channel 5m contours and Guyuansha terrain trends,and the division plan will keep Chongming and Qidong in clear boundary line.