A conceptual model of diagonal bar evolution Damia Vericat and I developed and have started to test on rivers in Spain.
I am seeking a Masters or PhD Student to shed light on diagonal bar dynamics. Diagonal what? Diagonal bars are by far the most common mid-channel bar throughout the world's rivers and streams, yet many people have never heard of them. Diagonal bars split flow around themselves in a characteristicallyasymmetrical fashion, creating complex in-channel habitat and leaving behind distinctive islands and floodplain topography. Diagonal bars start their lives as margin or bank attached bars on the inside-bend of flow, but then proceed to detach from the bank via a process of chute cutoff formation along the inside bend. They seem to evolve through a similar progression in extremely different fluvial environments. Diagonal bars are an excellent geoindicator of river-health in many reach types (e.g. wandering gravel bed rivers) as they often disappear when lateral adjustment is artificially confined. Basic empirical data on diagonal bars, their occurrence, their evolution and their prevalence is largely lacking from the geomorphic literature and restoration practitioners are largely unaware of their importance. This student would work with myself and Damia Vericat to build-out, refine, and rigorously test a conceptual model of diagonal bar evolution we developed, and build important insights into this poorly understood but pervasive bar form.
With growing interest in beaver as a cost-effective restoration and conservation tool, much is made of the geomorphic responses that beaver's ecosystem engineering and dam building will yield. Yet surprisingly, no coherent framework for predicting and explaining what sort of specific responses we expect in what environments. Specifically, a masters student would focus on 1-2 of the following topics and a PhD would likely tackle all 3:
Using geomorphic change detection on a long-term, repeat topographic dataset of geomorphic dynamics across 100's of beaver dams and beaver dam analogues to more clearly identify and explain geomorphic mechanisms of change that shape beaver dam complexes through their life spans.
Using the Wheaton et al. (2015) fluvial taxonomy and our Geomorphic Unit Toolkit, develop a stronger empirical and conceptual basis for the geomorphic unit assemblages (i.e. landforms) that consistently make up beaver dams and beaver dam complexes, how these evolve through time and how these assemblages differ across different reach types
Build network riverscapes models that predict geomorphic responses to different degrees of beaver dam building activity throughout a watershed.