Coastline Change Measurement and Generating Risk Map for the Coast Using Geographic Information System

Information on the pattern, rhythm and long-term trend of shoreline dynamics is vital to managing the coast, especially in mapping risk areas and in establishing the width of construction setback lines. Unfortunately, such data are often missing or where present of doubtful quality. In this paper, we share our experience in mapping coastline change in Singapore, using geographic information system (GIS). Most important before embarking on measuring coastline change is defining the coastline and deciding on a working definition where this line can be established on the ground, on maps or other sources of data. Complications arise where the coastline is extracted from different data sources to detect changes. In Singapore, coastline is defined is 2.515 m chart datum and this line which theoretically separates land from sea is shown on cadastral maps. The East Coast Park of Singapore is selected to illustrate the different techniques in measuring coastline change using GIS. Techniques include setting up a series of profile lines monitored and analyzed in GIS over a decade to detect changes, and using GIS to generate the 2.515 m chart datum line from a dense network of elevation points collected on the beach. Maps showing various rates of shoreline erosion are then derived and finally a Risk map for the coast generated.