A water management strategy to cope with severe climate change needs an efficient streamline model to play the important role of predicting the direction of flood-water. Generally a model is constructed using various image processing techniques which, depending on the particular area, can be quite complicated. In this paper two conceptually different approaches for determining streamlines from DEM data, in raster and vector forms, are reviewed. The advantages and limitations of both approaches are considered and compared using the numerical results of streamlines for the geometrically complex region containing Khao Luang National Park.