Abstract:

Hydrodynamic model was investigated to assign corresponding elevation of waterlines,which were extracted from multitemporal Landsat TM images at Chongming Dongtan,China.And the mean sedimentation rates were calculated at four transects in combination of waterlines with heights and situ measurement.Salt marsh vegetation classification was made through the integration of auxiliary data with remote sensing based on fuzzy mathematical theory.On the basis of vegetation investigation,fractional vegetation cover(FVC)was derived from high resolution Quick Bird images to indentify vegetation coverage.Then the effects of vegetation and elevation on sedimentation were discussed according to the above derived information.The results revealed that sediment accretion showed a shoreward and offshore reduction from the maximum site at the four profiles.A positive relationship was demonstrated between the mean accretion rates and surface elevation of low marsh and mudflat(〖WTBX〗R〖WTBZ〗2=0.8106).The hydrodynamic attenuation by vegetation and the effect of settling lag on suspended sediments were likely to result in a peak vertical accretion in the low marsh.The shoreward decrease in accretion from the peak site could be attributed to the low settling potential of finegrained suspensions resulted from the reduction in submergence frequency over the swamps.The offshore decreasing and negative accretion,however,could be related to the relative lower elevation and lack of vegetation.Spatial changes in sedimentation rate were also striking at the same elevations of different profiles,which could be attributed to differences in vegetation growth and hydrodynamics.In a summary,the synoptic capability of remote sensing integrating with hydrodynamic model provides a useful tool to facilitate field surveys,which may lead to better understanding of coastal processes.〖