C O N T E N T S - Physical Land Resources - Vrije Universiteit Brussel

area. Therefore, additional information from karst depression analysis is needed and itis concluded that there is a high potential for groundwater in the highly fracturedzones, which are close to karstic depressions or rivers. The general direction ofgroundwater flow can be predicted by the direction of the faults system anddepressions in the Suoimuoi catchment where regional tectonic structures control karstgroundwater flow. The ASTER image is used, after enhancement, to digitally extractlineaments. Based on indices of lineament densities, a fractured zone is defined inwhich cave development is expected. Areas with karstic depressions are extracted bycombining the result of DEM analysis and ASTER image ratio ¾. The methodology set upfor cave analysis in the sub-tropical karst of the Suoimuoi catchment, proves to be apromising method for predicting groundwater flow.The integration of Landsat ETM+ images with high resolution PAN and aerial photosprovide complementary information with respect to the discrimination of majorgeological features and allows lineament extraction in detail. With the high-resolutionimages, manmade and natural features are easy to recognize, especially in combinationwith areal photos. The Intensity-Hue-Saturation (HIS), Principal Component Analysis(PCA) and a Wavelet-based method are used for image fusion. Quantitative metrics forevaluating the quality of fused images are carried out. It is found that HIS is the mostoptimal method for image fusion in the Tamduong area, because it has a high potentialfor visual interpretation. A combination of remotely sensed data and fieldwork is usedfor geological mapping. The research methodology is applied to explore the subtropicalvegetated karst area of Tamduong. Based on the remote sensing analysis andfieldwork, a geological map is established. Fractured rock zones are mapped with thehelp of lineament indices densities. This research clearly shows that the study area ischaracterized by strong tectonic activity and faulted zones, whereby the geo-structureis controlled by NW-SE folding and fracture systems.This work not only gives details and insight in the understanding of karstgeohydrological characteristics of Suoimuoi and Tamduong, but also provides methodsof integrating remotely sensed data for geohydrological studies. The methods appliedin this thesis prove to be very useful for geohydrological studies in vegetatedmountainous sub-tropical karst areas of developing countries, like Vietnam.- 38 -