Abstract:

The widespread use of the GIS tools, besides the simple mapping of areas also enabled the visualization of various spatially referenced parameters for earth sciences. Parameters such as the slope or the drainage density of an area can be calculated with the GIS tools and can be depicted in maps. In many environmental problems though, the involved variables present inexact knowledge and spatial uncertainty. This is a problem appear also when we treat erosional processes, where a number of the system input variables are of fuzzy nature, such as the erodibility, the topography’s gradient, the drainage density and the vegetation - land use. The fuzzy nature of these physical parameters, if it is to be approached by mapping tools, requires the use of special methods that will assure that the geographical
distribution of the results will be accurate. Dealing with such uncertainties and the visualization methodologies that should follow them, is the ultimate aim of this paper. In the approach that is described here, MapInfo GIS software and Matlab are used in combination to study the erosional processes on a volcanic landscape, such us Thira Island, Greece. Mapinfo software was used for the creation of the input parameters. The management of the database was created during the digitization and the creation of the input parameters and finally for the rendering of the geographical output of the study in the form of thematic maps. Matlab software was
used for the calculations within the different parameters and the gradient leveling that were applied to the logical results. The transformation of the input variables to the output ones (erosion risk) was achieved by formulating a number of fuzzy logical rules. The final step of these processes is the development of the thematic maps.
Thira Island has been chosen for this case study, because its volcanic landscape and its susceptibility to erosional phenomena appeals great scientific interest and requires the introduction of different approaches for the solution of the natural problems. Besides, the output of this study can constitute an important tool for the local authorities of the island.