Analysis and trend prediction of shoreline evolution in Chongming Dongtan, Shanghai

Understanding Dongtan shoreline evolution has important significance for Dongtan wetland conservation and utilization. Based on object-oriented method, the shorelines of Dongtan are extracted from 6 scenes of Landsat-TM satellite images from 1987, 1990, 1995, 1998, 2003, and 2006, respectively. To model the shoreline changes, the authors developed an orthogonal-transect method, with which a series of transect is formed at a regular interval along 1987 shoreline and each transect goes along the direction parallel to the topographic gradient. The transect is then modeled with a graphics based fitting method and the shoreline dynamics are then analyzed. In addition, the spatial position of shorelines in 2010 and 2015 are also predicted. The results indicate that the shorelines of Dongtan are divided into the eroding segment in the south and accreting segment in the east and north. The eroding shoreline segments basically maintain unaltered and the accreting shoreline segments continue to expand by gradually decreasing speed. The maximum erosion rate and the maximum accretion rate are respectively 22.0 m/a and 247.2 m/a. The "suppressed" shoreline segments lie in the region of the boundaries of the island shadow. The future shoreline would evolve northeastwards to fit the 10 m isobaths unless the exceptive hydrodynamic conditions occur.