| Titre | River Entrenchment in small Mountain Valleys of the Western USA : Influence of beaver, grazing and clearcut logging / L'incision des cours d'eau dans les petites vallées montagnardes de l'ouest américain : l'influence des castors, du pâturage et des coupes forestières à blanc | |
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| Auteur | Richard A. Marston | |
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Revue |
Géocarrefour Titre à cette date : Revue de géographie de Lyon |
| Numéro | volume 69, no 1, 1994 Enfoncement des lits fluviaux : processus naturels et impacts des activités humaines | |
| Page | 11-15 | |
| Résumé anglais |
Channel entrenchment in small mountain valleys of the western USA can potentially be triggered by removal of beaver dams (by humans or by storm surges of water and sediment), severe overgrazing by livestock, or by clearcut logging. Beaver dams are removed by humans because they are perceived as a nuisance or because beaver can be used as bait for hunting bear. Storm surges of water and sediment can breach beaver dams, leading to a domino-effect on downstream dams. Beaver have been successfully transplanted to restore streams which have experienced entrenchment. Overgrazing by in upland areas accelerates runoff ; overgrazing in riparian zones reduces resistance of the channel bed and banks. Entrenchment caused by overgrazing can be prevented by altering grazing strategies. Clearcut logging is known to increase peak flows, but as with removal of beaver dams and grazing, only leads to channel entrenchment if the added runoff overcomes the resistance of mountain valley-bottom alluvium and vegetation. If channel entrenchment is allowed to progress, the water table will drop, riparian vegetation will change to less desirable species, fish habitat will be lost, and downstream sedimentation will occur. Source : Éditeur (via Persée) |
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| Article en ligne | http://www.persee.fr/web/revues/home/prescript/article/geoca_0035-113x_1994_num_69_1_4232 |
