A major problem in developing digital elevation models (DEMs) is the realistic representation of flow though complex terrain. A contour-based DEM, which uses natural flow lines and contours to define the element network in the model, is an elegant solution in that the governing equations of flow can be reduced to one dimension. Previous methods of constructing contour-based element networks require a high level of user involvement to produce the flow net. A new method for constructing contour-based element networks is presented that relies solely on contour data and does not rely on user-defined high points, saddle points, streamlines, or boundary files. Critical points such as high points and saddle points are automatically detected and a robust scheme is used to create flow lines. An improved method for calculating element attributes for the final DEM is also presented that takes into account the nonplanar nature of typical elements in contour-based networks. Furthermore, the inherent deficiencies of traditional flow line construction methods are discussed, and to an extent overcome, resulting in a more realistic model. Preparation time for DEM construction has been reduced, and the user is given greater control over the rules for calculating flow lines. The algorithm has been implemented on a typical desktop computer, and comparisons have been made with existing contour-based element network construction methods. Results show improved speed and robustness over traditional methods and emphasize the convenience of minimal data requirements. ¿ 1999 American Geophysical Union