On the determination of surface flow paths from gridded elevation data

Multiple flow direction algorithms are commonly thought to be a useful means of determining drainage areas from gridded elevation data. It remains however unclear whether these algorithms can be used to describe surface flow paths and gravity-driven processes across a terrain without producing excessive artificial dispersion of flow. To explore this issue, a unifying algorithm for the determination of flow directions is developed and new methods for the validation of surface flow paths are introduced. The unifying algorithm allows, by setting appropriate parameters, to perform local or path-based analyses, and to experiment different combinations of single and multiple flow directions in a morphologically significant manner. The new evaluation methods designate the drainage systems delineated from contour elevation data as a reference and consider the overlapping between these drainage systems and the corresponding drainage systems obtained from gridded elevation data. Results from numerical experiments indicate that multiple flow direction algorithms are useful to describe the between-cell variation of drainage areas across divergent slopes, but reveal that path-based single flow direction algorithms are more effective to describe surface flow paths across both convergent and divergent terrains.