Abstract:

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 factors in 22 tidal creek units. At last, Correlation/regression analysis was applied to quantify the contributions of influencing factors.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 would not have a significant alteration even if sediment discharge from the Yangtze River will decreased dramatically in the following decade.

Key words: tidal creeks, driving factors, remote sensing, fractal dimension, Chongming Dongtan, Shanghai