Joint spatial, topological and scaling analysis framework of river-network geomorphometry

Abstract

River networks are structural and functional backbones of river basins. They frequently display general scaling properties through their hierarchical topology. Their mathematical description further feeds geomorphology-based hydrological analyses and modelling approaches that require little calibration. Nevertheless, particular river basins display widely diverse geomorphometic structures in relation to relief, geology, climate and anthropogenic constraints, as well as various hydrological structure-function relationships. A robust, flexible and systematic approach is thus needed to allow for joint spatial, topological and scaling analyses, in order to explore the hydro-geomorphological diversity. The HydroStruct software application is dedicated to such analyses, and to easily link geomorphometric observations with hydrological analysis and modelling approaches, such as geomorphology-based transfer functions, accounting for rainfall variability within rainfall-runoff modelling, and impact assessment of landscape and hydraulic changes. HydroStruct was developed within the generic Ode-fiX framework, which provides Java software components to allow co-development and interfacing of object-oriented models.Les réseaux hydrographiques sont les ossatures structurelles et fonctionnelles des bassins versants. Ils présentent fréquemment des propriétés d’échelles à travers leur topologie de hiérarchie. De plus, leur description mathématique alimente une hydrologie à base géomorphologique, à travers des analyses et des modélisations peu exigeantes en calage. Cependant, les bassins versants présentent des structures géomorphométriques très variées, en lien avec le relief, la géologie, le climat et des contraintes anthropiques ainsi qu’une diversité de relations structure-fonction hydrologiques. Une approche robuste, flexible et systématique est par conséquent nécessaire pour faciliter des analyses conjointes spatiales, topologiques et scalantes et, ainsi, explorer la diversité hydro-géomorphologique. L’application logicielle HydroStruct est dédiée à de telles analyses, mais aussi à l’articulation des observations géomorphométriques avec des analyses et des modélisations hydrologiques telles que des approches basées sur des fonctions de transfert à base géomorphologique, la prise en compte de la variabilité de la pluie au sein de la modélisation pluie-débit et l’évaluation de l’impact de changements paysagers et hydrauliques. HydroStruct a été développé au sein du cadre générique OdefiX, qui fournit des composants logiciels en Java, dans l’optique de faciliter le co-développement et l’interfaçage de modèles orientés objet

Geomorphometry-based modelling of discharge series in ungauged basins – Robustness regarding DEM sources

“…For each basin and DEM, the river network was extracted with a minimum drainage threshold of 0.25 km 2 ; then the corresponding probability density function of hydraulic length L, pdf(L), was assessed, based on a morphometric analysis with GRASS 7.4.0 (Aouissi et al, 2013). Considering a water drop falling inside a basin and moving towards the outlet, the hydraulic length L corresponds to the travelling distance within the river network.…”

“…Considering a water drop falling inside a basin and moving towards the outlet, the hydraulic length L corresponds to the travelling distance within the river network. Following the assumption of a linear transfer function (Blöschl and Sivapalan, 1995;Robinson et al, 1995;Cudennec, 2007), pdf(t) = TF is then deduced from pdf(L) thanks to the estimation of the average river flow velocity v. This characteristic velocity has been regionalized for the whole Brittany by de Lavenne (2014) as in Eq. 2, where L is the mean hydraulic length of the considered basin.…”

Prediction of streamflow from the set of basins flowing into a coastal bay

“…This transfer function TF is built from morphometric analysis of the river network. Using GRASS 6.4 completed by the toolkit of Jasiewicz and Metz (2011), the flow path length inside the network L (so-called hydraulic length; Cudennec et al 2004, Aouissi et al 2013 is calculated throughout the basin from a digital elevation model (DEM). The DEM is at 50 m resolution, but is resampled at 25 m using bicubic sampling to increase the number of pixels inside small basins.…”

Regional watershed characterization and classification with river network analyses

“…Other available software in the discipline (e.g. Pike, ; Formetta et al , ; Aouissi et al , ) could have been used for some network indices, except that they are not dedicated to network analysis, and that they do not provide confidence levels allowing to identify significant (or non‐significant) indices to be used in the classification stage. Finally, we discuss our results in the light of differentiating generic and site‐dependent information extracted from our Haitian case study.…”