학술논문
Algorithms to route flow over Digital Landscapes: a comparisonand their implications for predicting ephemeral gullies/Comparaison d'algorithmes de l'écoulement appliqués à des M.N.T. : leur apport pour la prévision des ravinements temporaires
Document Type
article
Author
Source
Géomorphologie : relief, processus, environnement 2(3):41-50
Subject
Language
English
ISSN
1266-5304
Abstract
Résumé II s'agit de comparer six algorithmes de l'écoulement, traduisant la façon dont la matière peut être transférée sur des Modèles Numériques de Terrain. On peut distinguer trois groupes d'algorithmes de l'écoulement. Ces groupes produisent des résultats nettement différents, créant une distinction importante entre des algorithmes de l'écoulement multi-directionnel et de l'écoulement uni-directionnel. Les algorithmes de l'écoulement uni-directionnel ne peuvent pas aborder l'écoulement divergent et sont très sensibles aux erreurs de représentation topographique. L'approche vectorielle telle que les auteurs l'ont implantée, semble préférable car l'algorithme se transforme automatiquement en une méthode uni-directionnelle dans les cas de concavités importantes. Leur utilité quant à la prévision de la localisation des ravins temporaires est un peu contradictoire : les algorithmes de l'écoulement uni-directionnel, qui semblent se calquer sur le processus du ruissellement, ne donnent pas de résultats prévisionnels satisfaisants.
Abstract Six routing algorithms, describing how flow can be routed over Digital Elevation Models, are described and compared. The performance of these algorithms is determined based on both the calculation of the upslope area and the prediction of ephemeral gullies. Three groups of routing algorithms could be identified, which produce significantly different results with a major distinction between single flow and multiple flow algorithms. Single flow algorithms cannot accommodate divergent flow and are very sensitive to small errors and are therefore not acceptable for hillslopes. The flux decomposition algorithm, proposed here, seems to be preferable to other multiple flow algorithms. This method prevents using digitised drainage lines or predicting the location of channels in advance. The implications of the routing algorithms on the prediction of ephemeral gullies seem to be somewhat counterintuitive : the single flow algorithms that, at first sight, seem to mimic the process of overland flow, do not yield optimal results.
Abstract Six routing algorithms, describing how flow can be routed over Digital Elevation Models, are described and compared. The performance of these algorithms is determined based on both the calculation of the upslope area and the prediction of ephemeral gullies. Three groups of routing algorithms could be identified, which produce significantly different results with a major distinction between single flow and multiple flow algorithms. Single flow algorithms cannot accommodate divergent flow and are very sensitive to small errors and are therefore not acceptable for hillslopes. The flux decomposition algorithm, proposed here, seems to be preferable to other multiple flow algorithms. This method prevents using digitised drainage lines or predicting the location of channels in advance. The implications of the routing algorithms on the prediction of ephemeral gullies seem to be somewhat counterintuitive : the single flow algorithms that, at first sight, seem to mimic the process of overland flow, do not yield optimal results.