GIS AS A DECISION SUPPORT TOOL FOR PLANNING A COSTAL GREEN BELT BY USING SPATIAL AND THREE DIMENSIONAL MODELS

摘要

Costal environment is one of the most important geomorphological system which consisting unique vegetation cover. Especially in tropical islands like Sri Lanka, has its own variety of vegetation cover in diversified conditions. After the '2004 tsunami' devastation, a significant amount of vegetation has been washed away from the coastal zone and thereafter many governmental and non-governmental campaigns were conducted for rebuilding this environment. 'Green belt' was popular topic and implanted in many areas. But pre-planning process was always questioned because of the sustainability of them were getting down. Due to several low considered factors, such as human activities, geomorphological aspects as well as bio geographical factors many green belts were failed. This study was designed to identify a better pre planning mechanism for coastal green belts. The study was conducted in coastal zone of 'Kalutara' divisional administrative area which consisting several isolated green vegetation spots. Therefore, as a pre planning tool, Geographic Information Systems (GIS) were introduced in two dimensional (2D) and three dimensional (3D) aspects. As the first objective of the study, existing vegetation cover was identified using high resolution satellite images and field verification was conducted with a GPS survey. The vegetation spots were observed with the height levels for pre modelling activities. As the second objective the surface height of the Digital Elevation Model (DEM) and field measurements of the vegetation patches were combined and generated virtual surface model. As the third objective this model was forecasted to the other zones which excluded vegetation cover. But this was modelled with the several constrain factors which gives the realistic conditions of the study area. Socio-economic factors and other natural factors were also considered during the process. Topographical data, field observations and demographic data were used for multi criteria analysis and 3D modelling. ArcGIS software was used for spatial data handling and modelling activities. According to the results, several potential spaces were identified along the coastal zone which can be developed towards a green belt. These areas can be further examined with soil and other biological factors. As the conclusion, it was identified that the finalized model had a better representation of the study area and interpretation was less time consuming and convenient. These models can be altered according to the new criteria and repeatable to obtain different results. Therefore, preplanning mechanism is improved with GIS as a better decision support tool.