On depressional storages: The effect of DEM spatial resolution

Depression storage can be a significant storage element on a watershed surface, accounting for the retention of much water. Over the past decade, many models were developed to derive landscape features. However, relatively little is known about the impact of changing the spatial and/or temporal resolutions on subsequent features. In this paper, the surface topography was measured with the aid of a laser scanner with millimeter-resolution. Emphasis was laid on quantifying the effect of changing spatial resolution upon geometric properties of depressional storages. Digital mapping allowed the visualization of the location and topology of potential water surfaces and the manner in which water might move from one depression to another. From the pond analysis and associated spatial mapping, it became clear that most geometric characteristics relating to size and spatial location of depression storage, including area, volume and depth, are scale dependent. The relationship between the contributing area of each depression and the surface area of the same depression at each pour depth was established, and the organization inherent in such relationship was explored. Furthermore, it was found that these geometric objects may best be described by resorting to fractal geometry, a popular tool for quantifying variability across scales.