Deriving a global river network map and its sub-grid topographic characteristics from a fine-resolution flow direction map

Abstract

Abstract. This paper proposes an improved method for converting a fine-resolution flow direction map into a coarseresolution river network map for use in global river routing models. The proposed method attempts to preserve the river network structure of an original fine-resolution map in the upscaling procedure, as this has not been achieved with previous upscaling methods. We describe an improved method in which a downstream cell can be flexibly located on any cell in the river network map. The improved method preserves the river network structure of the original flow direction map and allows automated construction of river network maps at any resolution. Automated construction of a river network map is helpful for attaching sub-grid topographic information, such as realistic river meanderings and drainage boundaries, onto the upscaled river network map. The advantages of the proposed method are expected to enhance the ability of global river routing models by providing ways to more precisely represent surface water storage and movement.

Deriving global flood hazard maps of fluvial floods through a physical model cascade

“…The sub-grid parameterization is based on a 1 km Digital Elevation Model and all horizontal water transport is modelled by a diffusive wave equation to account for backwater effects. Yamazaki et al (2011) showed that this new model formulation (called CaMa-Flood) compares favourably to daily measurements of river flow gauging stations across the globe as well as indicating a good agreement between modelled and satellite observed flooded area. Water level simulations by CaMa-Flood in the amazon basin also show a good agreement with remote sensing altimetry (Yamazaki et al, 2012).…”

“…Pappenberger et al, 2010) or on observed flooded inundation fraction (e.g. Decharme et al, 2008Decharme et al, , 2011Dadson et al, 2010;Yamazaki et al, 2011). This paper describes a proof-of-concept exercise and we carefully consider the limitations of this approach.…”

“…ECMWF has successfully employed several routing algorithms based on the TRIP model Pappenberger et al, 2010). Yamazaki et al (2011) developed this global routing methodology further by including flood plains into the routing algorithm through sub-grid parameterization of the floodplain topography. The sub-grid parameterization is based on a 1 km Digital Elevation Model and all horizontal water transport is modelled by a diffusive wave equation to account for backwater effects.…”

“…The river network construction, river parameters and subgrid scale floodplain profiles are derived by the Flexible Location of Waterways (FLOW) method (Yamazaki et al, 2009). This method is used to upscale a high-resolution flow direction map at 1 km (Global Drainage Basin Database, GBDB, Masutomi et al, 2009) into a coarse-resolution river network map, which is used in the global-scale river routing model.…”

The World Karst Aquifer Mapping project: concept, mapping procedure and map of Europe

“…For example, some previously published maps focus on precipitation and the atmospheric water cycle (Kubota et al 2007), river networks (Yamazaki et al 2009), dams and reservoirs (Lehner et al 2011) or other relevant aspects. A map of BGroundwater Resources of the World ( Richts et al 2011;WHYMAP 2008) has been prepared within the framework of the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) coordinated by UNESCO-IHP (BGR 2016).…”