The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models

TLDR

Distributed hydrological models rely on accurately specified flow pathways, as flow‑path definitions underpin the spatial indices used to predict moisture status in models such as TOPMODEL. The study investigates challenges in deriving flow pathways from raster digital terrain data for TOPMODEL predictions and proposes a strategy to account for subsurface flow deviations. The authors assess how flow‑path algorithms and grid resolution affect the TOPMODEL moisture index and illustrate a strategy to adjust for subsurface flow deviations with an example application.

Abstract

Abstract The accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways. This paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using TOPMODEL. Distributed moisture status is predicted in TOPMODEL on the basis of spatial indices that depend on flow path definition. The sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients. A strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application.