My question is inspired ( and similar) with my previous question. But this question is more concerned about the suitability of D8 ( or in general non-dispersive) flow accumulation algorithm for terrain with a lot of flat area, such as highly developed township.
For watershed analysis, the post here says that D8, as a non-dispersive algorithm, is better over other dispersive algorithms, such as D-infinity algorithm:
Non-dispersive flow algorithms are particularly suited to watershed delineation for this reason. With a dispersive flow algorithm, grid cells near the boundary of a watershed can actually belong to both watersheds, i.e. two of the multiple flowpaths that issue from a grid cell situated near a watershed boundary may actually terminate at different outlets entirely. In reality of course watershed boundaries are somewhat fuzzy and ambiguously defined, but we generally want delineated watersheds that are mutually exclusive. Since the fuzziness caused by the flow dispersion inherent in the flow algorithm isn't necessarily related to the physical processes that actually govern the ambiguity of flow near watershed boundaries, we have no basis for interpreting the dual membership of bordering grid cells. That is, we can't say, 'this grid cell belongs to this watershed 90% of the time and its neighbouring watershed 10% of the time' solely based on the artificial nature of the dispersion imposed by the algorithm design. Dispersion is particularly problematic therefore.
But this is in direct contradiction to the answer I received:
D8 is very sensitive to errors in the input digital elevation model. All the accumulated flow is directed to one neighbor, and sometimes the pixel is erroneous, which mean all the flow accumulation can be directed to a wrong pixel. Other algorithms, which distribute flow to more than one neighbor, are more robust. For example consider an area of 10 by 10 m (10 m resolution), quite often the water is not flowing to one direction, but to two or even more. I'd prefer multiple flow direction algorithm (by Quinn, Freeman), or the Tarboton's D infinity.
So which is correct? is D8 ( non-dispersive) flow accumulation algorithm still suitable for watershed computation, especially if terrain contains lots of flat area?