北仑港区岸滩演变和水下岸坡冲淤分析

Coastal evolution and erosion-deposition analysis of underwater slope in Beilun Port

北仑港区是一个典型的峡道型淤泥质海岸港口,研究该区域的岸滩演变和水下岸坡冲淤变化对于认识工程环境效应具有十分重要的现实意义。利用1935年、1962年、1987年、1996年和2004年5个年份的水深地形资料,应用GIS技术建立了这些年份北仑港区的数字高程模型,结合地方史志和三维潮流泥沙数值模型,计算并分析了北仑港区不同时段的岸线变迁、潮滩演变、水下岸坡冲淤变化和冲淤动态趋势。结果表明,岸线位置在1935—1976年间由于围垦筑堤而持续向海推进,而在1976年以后,总体保持稳定,只因码头建设而发生局部形态改变;受此影响,潮滩面积从1935年的18.16 km^2锐减至2004年的3.83 km^2;水下岸坡在1935—2004年间经历了缓慢冲刷—轻微冲刷—较快淤积—轻微淤积的调整过程,这种变化主要是受北仑港区建设和杭州湾滩涂围垦等人类活动的影响。

Beilun Port is a typical harbor alongside the tidal channel on muddy coast.It is great realistic significance tounderstand the engineering environmental effects via studying the coastal evolution and erosion-deposition analysis ofunderwater slope.Based on5bathymetric maps of1935,1962,1987,1996and2004,GIS technology is taken to establish thedigital elevation models of Beilun Port in these years.With local chronicles as well as3D hydrodynamic,sediment transportmodel,we calculated and analyzed the changes of coastline,evolution of tidal flat and erosion-deposition of underwater slope.The results indicate that the position of coastline is advancing seaward due to reclamation and embankment during1935-1976,while keeping relatively stable except in shape because of dock project after1976.Affected by the changes of coastline,thetidal flat area is sharply reduced from18.16km2in1935to3.83km2in2004.Meanwhile,the underwater slope experiences anadjustment from slowly erosion to slightly erosion then to fast deposition and then to slightly deposition.This change is mainlyas a consequence of human impact,such as port construction and reclamation in Hangzhou Bay.