Flow accumulation is an important terrain attribute that has many applications. The computation of flow accumulation, however, is time consuming, which especially becomes an issue as high-resolution DEMs are getting increasingly available. In this study, we conducted experiments of sweeping the DEM starting from different corners and in different ways - by rows or by columns - when doing the cell-wise calculation. It turned out that a combination of different sweeps can be considerably more efficient than the conventional algorithm that employs single-type sweeping.