Detection of coastal wetland change in China: a case study in Hangzhou Bay

Wetland monitoring is crucial for understanding wetland changes and responses to natural and anthropogenic actions. In this research, Hangzhou Bay coastal wetland was selected as the study area to analyze spatial patterns and dynamic changes based on Landsat multitemporal imagery. A hybrid approach combining expert knowledge, decision tree, threshold technique, unsupervised classification and postprocessing was developed for wetland classification. Three typical sites were selected to analyze different change patterns. Over the last 10years, the wetlands have undergone dramatic changes, continued to expand outwards due to natural accumulation and increased in area. At the same time, these wetlands have also partially decreased with artificial reclamation and urban construction. An analysis of typical sites found that the change in the western part of this region was dominated by natural accumulation and that in the central and eastern parts was dominated by reclamation due to geographical location and hydrological power. In general, wetlands are continually changing under the joint action of natural accumulation, artificial reclamation and urban construction. The local terrain, hydrology, soil, population, economy and policy also influence wetland changes. The results of wetland monitoring are essential for the protection and management of local wetlands.