Uncertainties Associated with Hydrological Terrain Analysis in Flat Topography Wetlands
Sammanfattning: Describing how water flows in flat landscapes is generally difficult as the main driving force behind surface runoff is elevation differences. In an experiment designed to delineate the uncertainty in catchment areas created in software for geographical information systems (GIS), a flow algorithm that distributes the flow from one point to all of the neighbours with lower elevation was used. By analysing the values for the catchment areas created by this algorithm the uncertainty could be assessed. The main objective is therefore to investigate whether flow direction algorithms can be used to delineate uncertainty in catchment areas or not. The results acquired in this project consisted of area sizes for the different catchment areas connected to each wetland, as well as the distribution of values within these areas. The values signifies the percentage of each cell within an area that contributes to the drainage point. By relating the dispersion of values for certain thresholds to the size of the area, the main conclusion is that areas of small size are more affected by uncertainty. Finally, some further studies within this area has been suggested. For example, to evaluate differences in runoff in different kinds of terrain, with different data resolutions or to correlate it to the effect of slope. In conclusion this project supplies an entrance to a new method of evaluating uncertainty in a field that surely can be broadened and repeated for greater accuracy.
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