日照港西部海域海底地形与表层沉积特征

利用单波束测深仪和蚌式取样器进行了日照石臼港扩建码头西侧约50km~2海域1:2 000~1:10 000的水深地形测绘和底质分析工作。调查结果表明,日照港西部海域可分4个水深区,其地形和沉积特征如下:1)航道区,浅水航道区等深线平行于码头岸线,水深11m,经过疏浚已形成向南倾斜的四级阶梯地形,疏浚中心处水深24m。航道区底质以分选中等的砾砂为主;2)港池区,水深6 m,等深线与港池岸线平行,水深向南渐增,海底地形平坦,坡降比3‰。底质以分选较好的粉砂和砂质粉砂为主,近岸有少量分选较差的泥质砂质砾;3)涛雒-付疃河口区,水下三角洲地形明显,5m以浅等深线呈弧形向东南方向凸出,坡降比最大可达14.2‰,底质类型为分选极好的砂和粉砂质砂;4)浅海区,海底地形平坦,平均坡降比1.9‰,6~10m等深线呈NE-SW向平行向外海增大,近南扩码头端向东偏转,底质类型为分选好的砂质粉砂和粉砂,并呈平行于海岸线向深水区呈粗-细-粗的带状分布。底质类型分布与水深条件基本吻合,但深水区出现的底质粗化现象,分析认为可能与南扩码头的挑流作用有关,海底沉积物呈向南运移趋势。

Seafloor Topography and Surface Sediment Characteristics in the Western Sea Area of the Rizhao Port

The bathymetric and bottom sediment data are of great significance for port channels,anchorage planning and environmental assessment after the port construction. However,there is a lack of such data for the southward-expanded waters of the Rizhao Port.In order to provide helpful suggestions for the rational layout in the southward-ex-panded waters of the Rizhao Port,bathymetric survey and bottom sediment investiga-tion were carried out in the western 50 km2 waters of the southward-expanded sea area of the Rizhao Port by using single beam echo sounding and clam type sediment sampler. The results show that the western sea area of the Rizhao Port can be divided into four water depth zones,in which the seafloor topography and sediment characteristics can be described as the followings:1)the Channel Zone:the shallow channel zone is about 500 m wide and has a water depth deeper than 1 1 m.The isobathic lines there are parallel to the dock water front and four grades of stepped topography inclining southward are formed.In the dredging center of deep channel the water depth reaches to 24 m and a-round the dredging center the isobathic lines show a semielliptical shape with an opening to the south.At the entrance of the opening the water depth is 23 m.The bottom sedi-ments in this zone are dominated by medium sorted gravelly sand;2)In the Harbor Ba-sin Zone,which includes the nearshore area from the southern Rizhao Port to the ash dam of power plant and is highly concentrated with fishing harbors,the water depth is shallower than 6 m and increases gradually toward the south.The isobathic lines are parallel to the harbor shoreline.The seafloor is even,with a gradient ratio being 3‰. The bottom sediments are dominated by well sorted silt and sandy silt,with small a-mount of poor sorted muddy and sandy gravel occurring in the nearshore area;3)In the Estuary Zone from the Taoluo River to the Futuan River,underwater delta topography is evident.The isobathic lines shallower than 5m show an arc-shape and protrude south-eastward,with the maximal gradient ratio being 14.2‰.The bottom sediments in this zone consist mainly of excellently sorted sand and silty sand;4)In the Shallow Water Zone,the seafloor is even,with the average gradient ratio being 1.9‰.The 6 ~ 10 m isobathic lines extend parallel toward the offshore along the northeastern direction and then deflect eastward near the southward-expanded dock.The bottom sediments are mainly composed of well sorted sandy silt and silt and show a coarse-fine-coarse banded distribution toward the deep waters and parallel to the coastline.The sediment distribu-tion is basically consistent with the water depth conditions.However,the coarsening of sediment in the deep waters may probably be due to the current deflection caused by the southward-expanded dock.The bottom sediments tend to move southward.