Figure 3.11: 8-Direction Pour Point Model (Anderson, 2000)
Most basin delineation techniques for grids are based around the 8- Direction Pour Point Model concept. However, the 8-Direction Pour Point Model has been criticized because it permits only one flow direction leaving a cell. Garbrecht et al. (1999a) note that this is satisfactory if being used for large drainage areas with well-defined channels, but the model may be less appropriate for overland flow analysis on hill slopes. A second method for determining flow direction is the D-∞ Model developed by Tarboton (1997). Figure 3.12 below depicts this model.