2019 CSDMS meeting-015
Computing more realistic flow-routing surfaces using FlowFill
Flow routing calculations are routinely performed in geomorphic and hydrologic analyses. These require an appropriate flow-routing surface, which is generally a digital elevation model which has been pre-processed to remove all depressions from its surface. This allows the flow-routing surface to host a continuous, integrated drainage network. However, real landscapes contain natural depressions that can store water and break up the drainage network. These are an important part of the hydrologic system, and should be represented in flow-routing surfaces. The challenge is in removing from a DEM only those depressions which would be filled under reasonable hydrologic conditions at a given location, and not all depressions indiscriminately. To address this problem, we developed FlowFill, an algorithm that routes a prescribed amount of runoff across the surface in order to flood depressions, but only if enough water is available. This method conserves water volume and allows a user to select a runoff depth that is reasonable for the region of interest. Typically, smaller depressions or those in wet areas or with large catchments are flooded, while other depressions may not be completely filled, thus permitting internal drainage and disruptions to hydrologic connectivity. Results are shown at a sample location using a range of runoff depths, with the resulting flow-routing surfaces with filled and unfilled depressions and the drainage network structure associated with the result.