Monitoring Mudflat Landforms Using Remotely Sensed Imagery

This paper applies remote sensing techniques to mudflat landforms in the coastal area adjacent to the Radial Sandbanks in northern Jiangsu Province. Supported by remote sensing image processing system (Erdas), Geographical Information System (ArcGis) and ground truth investigation, 14 Landsat and SPOT satellite images that cover this area (between 1975 and 2003), are analyzed to extract information on mudflat landforms including tidal flats, linear sandbanks, salt marshes, shoreline and water line, and to examine their spatial distribution and dynamic evolution patterns. The results show that the phenomenon of tidal water level difference is significant over the study area, which restricts the application of remote sensing to mud flat environment studies on the Radial Sandbank coast. With the aid of artificial cognition, unsupervised classification method can be used to derive effectively the water line on mudflat. The Modified Soil-Adjusted Vegetation Index (MSAVI) is a reliable indicator for salt marsh vegetation information in tidal flat environments. Although the growth of mudflat causes the salt marsh to expand towards the sea rapidly, large scale reclamation schemes continuously occupy the developing space of salt marsh vegetation from land side, which results in the degradation of the salt marshes. In response to the combined effect of human activities and natural processes, the shoreline of this area has a tendency to become straight, and the rate of land reclamation is higher than the rate of tidal flat land resource increase due to accretion in recent years. From 1975 to 2002, the upper part of the tidal flat in northern and southern flanks of the radial sandbanks adjacent to the shoreline has a trend of accretion, but on the central coast and offshore sandbank areas the upper tidal flats are eroding. Since 1999, some unique ground features have been formed on lower tidal flats in this area, with an increasing scale. These may result from the recent development of mariculture on the tidal flat over the region.