The proposed Bengoh Dam which is located at Bungoh catchment with the latitude between 1.184° to 1.296° N and in longitude between 110.106° to 110.242° E . The dam is designed to operate as a water reservoir dam for meeting the long-term water supply need of Kuching City and its vicinities. The catchment of the proposed Bengoh Dam is approximately 127km2. The construction of this dam is expected to inundate an area of approximately 8.77 km². The entirely Bengoh Catchment is constitutes of primary forest, old secondary forest, young secondary forest and agroforestry. Using the application of GIS, the vegetation within the dam layout was delineated leading to the determining of the area cover by the respective vegetation cover such as primary forest, young secondary forest, old secondary forest and agroforestry. In this study the inundated area was quantified by taken into consideration the contour that marks the reservoir maximum level which is 80 meters above sea level. Five alternative of Dam site are being proposed. Alternative 1 exhibits the highest percentage of submerge area which is 59.962% followed by alternative 3 (36.080%). Alternative 2 causes 33.921% inundated area while alternative 5 contributes 30.592%. Alternative 4 indicate 28.188% area being submerged which is the least among all the five alternatives. The least area being submerged is considered to be the most appropriate site for the dam.