江苏中部海岸潮沟的形态变化特征

作为一种典型的潮滩地貌单元,潮沟(tidal creeks) 在江苏中部海岸潮间带广泛发育,并表现出复杂的摆动性。本文根据1981-2010 年遥感影像和野外观测数据,对该区潮沟的平面形态变化进行了分析。结果显示,江苏中部海岸潮沟(根据其长度差异) 一般分为4 级,1~3 级潮沟的个数分别为21、97 和688 (1:5:33),其平均长度分别为7587±1544 m、1921±916 m和327±200 m;潮沟在中潮带比较发育,其密度和分汊率明显大于高潮带和低潮带;主潮沟曲率从高潮带向低潮带呈减小趋势;外来引种互花米草扩展和大规模滩涂围垦活动对潮沟产生了较大影响,其中后者明显地抑制了潮沟的发育。研究区潮沟的摆动性具有明显的区域和级别差异。与研究区北部的潮滩区域相比,海岸潮差较大的南部潮滩区潮沟的摆动性较大;同一个潮沟系统其1 级潮沟的摆动性>2 级潮沟>3 级潮沟;同一条潮沟其下段的摆动性>中段>上段;同一区段弯曲岸段的摆动性>顺直岸段;1 级潮沟上段、2 级潮沟中上段、3 级潮沟或位于盐沼内的潮沟其摆动性不明显。

A morphological analysis of tidal creek network patterns on the central Jiangsu coast

This paper details the two-dimensional geomorphology of the tidal creek systems and their migration characteristics using MSS, TM/ETM + data of 1981-2010 and field investigation. The results show that the tidal creeks in this area could be divided into four grades according to their lengths: 7587±1544 m, 1921±916 m and 327±200 m with numbers of 21, 97 and 688 (1:5:33), respectively. The tidal creeks within the study area were well developed in the middle tidal belt, and their drainage density and bifurcation ratio were much greater than those in the high and low tidal belts. The curvature of main tidal creek decreased from high tidal belt to the low one. The development of tidal creeks are influenced by the exotic introduction of Spartina alterniflora, and obviously restrained by the reclamation activities. The lateral migration or sway of the tidal creeks exhibited significant difference in rank and region. Compared with the tidal creek systems in the northern part of the area studied, those in the southern part with a larger tidal range have a larger lateral movement ranges and migration rates; as for a tidal creek system, the sway intensity of a first-order creek is greater than that of a second-order creek, followed by a third-order creek; for a single tidal creek, the case is the lower segment > the middle segment > the upper segment; and within an individual segment, the migration intensity of the curving segment is greater than that of the straight segment. The lateral migration is not obvious in the upper segment of the first-order creeks, the middle and upper segment of the second-order creeks, the third-order creeks and the creeks in the S. alterniflora salt-marsh.