Path‐based methods for the determination of nondispersive drainage directions in grid‐based digital elevation models

Abstract

[1] Path-based methods for the determination of nondispersive drainage directions in grid-based digital elevation models are presented. These methods extend the descriptive capabilities of the classical D8 method by cumulating the deviations between selected and theoretical drainage directions along the drainage paths. It is shown that either angular or transversal deviations can be employed. Accordingly, two classes of methods designated D8-LAD (eight drainage directions, least angular deviation) and D8-LTD (eight drainage directions, least transversal deviation) are developed. Detailed tests on four synthetic drainage systems of known geometry and on the Liro catchment (central Italian Alps) indicate that the proposed methods provide significant improvement over the D8 method for the determination of drainage directions and drainage areas.

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

“…The threshold value is introduced to exclude pixels which compose a flow path just entering and leaving a corner of a cell, because they are not favorable cell outlet pixels (Paz et al, 2006). The threshold value is set at about half the size of cells at the equator (e.g., 50 km for a target resolution of 1 degree).…”

“…Although various criteria have been introduced to reduce errors caused by upscaling procedures, the basic framework of most upscaling methods still consists of two procedures: firstly, selecting the outlet pixels for each coarse-resolution cell; and second, determining the downstream cells for each cell by tracing fine-resolution flow paths. Despite the improvements in upscaling methods, none have achieved error-free delineation of coarse-resolution river network maps (Paz et al, 2006). Breakdowns of the original river network structure can often be found in the coarse-resolution grid cells within which multiple rivers coexist.…”

“…Fine-resolution flow direction maps (grid size, ≤1 km) have been successfully constructed by applying the steepest slope method to Digital Elevation Models (DEM) (e.g., Jenson and Domingue, 1988;Costa-Cabral and Burgas, 1994;Tarboton, 1997;Orlandini et al, 2003). Although global fine-resolution flow direction maps such as HYDRO1k and HydroSHEDS (Lehner et al, 2008) are available, they cannot be used directly in global-scale models because of the excessive computation time required as a result of the fine detail.…”

“…The procedure of converting fineresolution into coarse-resolution is referred to as an "upscaling method." Various upscaling methods have been proposed to derive river network maps for use in macro-scale river routing models (O'Donnell et al, 1999;Wang et al, 2000;Fekete et al, 2001;Döll and Lehner, 2002;Olivera et al, 2002;Olivera and Raina, 2003;Reed, 2003;Paz et al, 2006;Davies and Bell, 2009). All of these upscaling methods derive river network maps using the "deterministic eight neighbors" (D8) form, in which the downstream direction of a grid cell is determined by one of the eight neighboring grid cells.…”

“…1b). To determine outlet pixels or downstream cells, some upscaling methods take into account decision criteria, most of which attempt to neglect flow paths just entering and leaving the corner of a cell (e.g., Olivera et al, 2002;Reed, 2003;Paz et al, 2006). Although various criteria have been introduced to reduce errors caused by upscaling procedures, the basic framework of most upscaling methods still consists of two procedures: firstly, selecting the outlet pixels for each coarse-resolution cell; and second, determining the downstream cells for each cell by tracing fine-resolution flow paths.…”