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Accueil du site → Doctorat → États-Unis → 1997 → Integration and fragmentation in a fluvial geomorphic system, Verde River, Arizona

Arizona State University (1997)

Integration and fragmentation in a fluvial geomorphic system, Verde River, Arizona

Beyer, Patricia Judith

Titre : Integration and fragmentation in a fluvial geomorphic system, Verde River, Arizona

Auteur : Beyer, Patricia Judith

Université de soutenance : Arizona State University

Grade : Doctor of Philosophy (PhD) 1997

Résumé
This research investigates the spatial and temporal nature of fragmentation and integration in the Verde River system in central Arizona. A fragmented river system exhibits spatial and temporal variability in controlling factors and resulting processes which distinguish sections of the river from other sections. This study examines three aspects of the Verde River system in order to explain system fragmentation : hydrology, channel morphology, and channel stability. Hydrologic analyses, using data from 11 U.S. Geological Survey gaging stations, indicate system fragmentation by the high variability in the relative size and frequency of flows greater than the mean annual flow, particularly between perennial tributaries in the middle basin and the main stem. Morphologic and stability analyses drew from discharge and shear stress calculations generated by modeling flow through 14 surveyed cross-sections along the Verde River, representing six river segments with distinct hydrologic and geologic characteristics. At-a-station hydraulic geometries for the Verde River highlight the impact of reach-scale factors on channel morphology. Stability ratios, generated using shear stress calculations and sediment data from each cross-section, indicate that geomorphic features within cross-sections (specifically channel beds, active channel side bars, and flood plains) exhibit greater variability in their mobility than features between cross-sections. All active geomorphic surfaces become unstable at discharges with a recurrence interval greater than five years. Modified at-a-station hydraulic geometry analyses using cross-section subsection discharge and shear stress values show great within cross-section variability. Competence and capacity increase at a fairly uniform rate for similar features throughout the system, indicating an overall efficiency in sediment transport. Like morphology, variations in stability and sediment transport are largely related to combinations of local (reach-scale) factors, including channel pattern, gradient, valley width, tributary inputs, and human activity, rather than basin or subbasin scale, factors. Identifying the patterns of variability within the river system and relating those concepts to system fragmentation increases understanding of river behavior, highlights the limitations of present approaches to system modeling and management, and provides decision-makers with a framework for assessing the impact of human activity on river systems.

Mots clés  : Environmental science, Hydrology, Health and environmental sciences, Geography, Earth sciences

Accès au document : Proquest Dissertations & Theses

Page publiée le 14 avril 2015, mise à jour le 9 octobre 2018