Modeling Mass Movement Transport Processes in An Alpine Environment Using Graph Theory: Savage Basin, CO, USA
Abstract
Mass movement, which is a major geomorphic process in the San Juan Mountains of southwestern Colorado, plays a major role in landscape evolution of the mountain range. Alpine drainage basins are prime areas for sediment cascades, where debris is transported from cliffs in higher elevations to a variety of downslope storage landforms, or sinks, via various massmovement processes, into stream channels in lower elevations, and exiting the basin. Distinct landforms are coupled and connected by geomorphic processes; thus, geomorphic coupling and connectivity are two important concepts for studying landforms and their functions in alpine basins. The study area is a glacial cirque known locally as Savage Basin. Unfortunately, no one has examined the sediment cascades in an alpine basin from source areas along mountain ridges, to stores in hillslopes, and eventually to sink areas along the basin floor. In this thesis, a mathematical method, graph theory, is applied to understand cascade pathways and landform linkages. A sediment-cascade simulation graph is constructed based on graph theory.
Establishment of a landforms map for the study area is fundamental to constructing the graph and identifying sediment sources as well as pathways and transport processes. By mapping landforms and analyzing nodes and edges in the graph, I conclude that debris flows are the major mass movement process, and talus deposits provide most of the sediment supply to other landforms. The graph constructed in this thesis suggests that most landforms serve as contributing zones or intermediate zones for sediment cascades. Moraines serve as depositional zones, which receive sediment from surrounding landforms. The cascade graph also suggests that the sediment cascades in Savage Basin have a high geomorphic coupling efficiency and low connectivity. Landscape evolution of Savage Basin is explained in this thesis based on the sediment cascades analysis and geomorphic history of the study area. The methodology and the application of graph theory in this thesis research provide a general theoretical framework for analysis of geomorphic processes and cascade systems for other basins in an alpine environment.
Citation
Qu, Tianyue (2019). Modeling Mass Movement Transport Processes in An Alpine Environment Using Graph Theory: Savage Basin, CO, USA. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /183794.