崇明东滩潮沟发育特征及其影响因素定量分析

Spatial Distribution of Tidal Creeks and Quantitative Analysis of Its Driving Factors in Chongming Dongtan,Shanghai

在长江来沙量减少的新形势下,研究崇明东滩潮沟地貌的发育与影响因素具有一定的现实意义。利用航空遥感、卫星遥感数据、表层沉积物采样数据和滩涂高程测量数据,在GIS技术的支持下,提取了潮沟现状以及影响因子信息。在此基础上,利用线性回归和因子分析等手段定量分析了潮沟发育与影响因子之间的关系。研究结果表明:崇明东滩潮滩植被、底质类型是影响崇明东滩潮沟发育的主导因素,潮沟密度与植被绿度指数、归一化植被指数及表层沉积物粒度的相关系数R分别为-0.910 6、-0.891 9与0.873 4;人类活动也对潮沟时空分布发育特征造成了一定影响;潮沟发育与地形、沉积速率关系不甚密切。在长江口来沙量减少的背景下,该区潮沟地质景观不会出现大的改变;要维护滩涂的稳定性,制约潮滩发育的有效手段可以通过控制植被来实现。

The decrease of Yangtze River sediment discharge into the sea and the consequent impacts on the tidal flat have become a hot topic in recent years. The objective of this paper is, from the aspect of tidal creek development, to examine the morphological responses as well as its driving factor in Chongming Dongtan. We firstly interpreted tidal creeks from the aerial image acquired in 2008, and then, under the support of remote sensing and geographic information system software, various influencing factors for tidal creeks development were extracted： vegetation index and soil wetness were generated using Landsat Thematic Mapper（TM） image; the slope of topography was calculated from newly measured digital elevation data; and the isogram map of sedimentary size was produced from grain-size data on sediment samples. After doing these, zonal statistics method was used to calculate the average value of influencing {actors in 22 tidal creek units. At last, Correlation/regression analysis was applied to quantify the contributions of influencing {actors. The result shows that vegetation, hydrodynamic condition, sediment type are the dominant factor contributing the current distribution pattern of tidal creeks, followed by man--made projects, while topography and deposition rate are not main driving factors for the creeks evolution. The R of creek density with vegetation greenness, normalized differential vegetation index and surface sediment size are --0. 910 6, --0. 891 9 and 0. 873 4,respectively. From this, we can infer that the distribution pattern of tidal creeks significant alteration even if sediment discharge from the Yangtze River will decreased following decade. would not have a dramatically in the following decade.