The New Hydrographic Hydrosheds Database Derived from the Tandem-X Dem

The HydroSHEDS database provides seamless hydrographic data to support hydro-ecological research and applications on a regional to global scale. A steadily increasing availability and accuracy of remote sensing data promotes the development of a second and refined version of HydroSHEDS, which is based on the TanDEM-X dataset. To derive hydrographic information from the topographic data, the TanDEM-X digital elevation model (DEM) requires editing, which is summarized in the so-called hydrologic pre-conditioning. The processing steps include an infill of voids and outliers in the DEM and the delineation of a global high-resolution coastline. Furthermore, a global water mask is generated to edit rough and noisy appearing open water surfaces in the DEM. An urban correction layer is calculated to reduce distortions in river flow paths due to built-up areas. Within the HydroSHEDS workflow, the preconditioning will be complemented with refined hydrological optimization and correction algorithms. Compared to HydroSHEDS v1, the resulting hydrologically conditioned DEM ensures a more accurate derivation of flow direction and flow accumulation maps.