Hydrological consistency of digital elevation models to define drainage network in the subbasin of the Terra Dura forest stand in Eldorado do Sul, RS

The development of water erosion occurs in response to the way water moves through and over a given landscape. The digital elevation model (DEM) must therefore be as accurate as possible, since it is the basis for the analysis of a relief. The objectives of this study were to define a hydrologically consistent digital elevation model (HCDEM) and the most appropriate method to determine the flow direction of the drainage network in the sub-basin of the Terra Dura forest stand, in Eldorado do Sul, RS. The generated models were tested with Topogrid interpolation, Triangulated Irregular Networks (TIN) linear (TINL) and natural neighbor TIN (TIN NN). The quality of the hydrological analysis was evaluated by comparing the contours generated by the test models with the original curves of the sub-basin (scale 1:10.000); assessment of the amount of flat areas; and comparison of the original drainage with that generated by the models using the Deterministic (D8) and Deterministic infinity (D∞ or infinite D) flow direction methods. The hydrological consistency of Topogrid was the best of the studied models, as indicated by the better contour continuity (fewer contact points) and more details of the drainage area and water divides, resulting in a lower number of flat areas and more detailed flow paths, independently of the method used to determine the flow direction. In relation to the drainage network, the description of the flow paths by the D∞ distributed method was better than that by the D∞ single direction method. In conclusion, the Topogrid HCDEM associated with the D∞ method identified the preferential flow paths that form the drainage network most precisely.

Topogrid; linear TIN; natural neighbor TIN; flow direction