Sensitivity of habitat hydraulic model outputs to DTM and computational mesh resolution

Abstract

AbstractIn this study, a state‐of‐the‐art approach in modelling fish habitats, using high‐resolution topographical data, obtained from unmanned aerial vehicle, was applied. Habitat Suitability Indices are used to predict how changes in discharge affect instream fish habitats. Habitat Suitability Indices regarding depth and velocity for two size classes (small sized fish 5–15 cm total length and large sized >15 cm total length) of Salmo pelagonicus and Barbus balcanicus were used, in combination with a two‐dimensional hydraulic‐hydrodynamic model, for the estimation of the weighted usable area (WUA) in a mountainous stream. Computational mesh and/or digital terrain model (DTM) resolution selection may influence the accuracy of WUA results, especially in boulder and cobble‐bed streams with complex habitat structures. The aim of the study is to examine the sensitivity of various hydraulic‐hydrodynamic modelling geometry configurations on WUA at ungauged or poorly gauged streams. Comparisons of three different geometry configurations: (1) identical computational mesh and DTM resolution (SensComb); (2) finest computational mesh resolution combined with different DTM resolutions (SensDTM); (3) finest DTM resolution combined with different computational mesh resolutions, as part of two‐dimensional hydrodynamic modelling, were applied to test the differences in WUA (SensMesh). WUA maps were generated for both fish species and class sizes for each modelling geometry configuration and compared with each other for assessing the sensitivity of the two‐input data (computational mesh and DTM). Results provided by both indices and their spatial distribution indicated the optimal DTM and computational mesh resolution as well as the sensitivity of a specific hydraulic‐habitat model on them.