Geomorphic Covariance Structure Analysis of River Terrains for Process Evaluation and River Design

Abstract:

The term "Geomorphic Covariance Structure" (GCS) means the linked bivariate pattern of any two river variables along a pathway, and it applies to both abiotic and biotic variables. It is not the statistical covariance, which is a single number, but instead a new concept involving the complete bivariate spatial series. For example, one GCS could be the serial co-occurrence of variations in large wood abundance and width. Another could be the serial co-occurrence of salmon redds with the product of standardized width and depth. Importantly, the GCS between detrended standardized bed elevation (a surrogate for depth) and standardized width is the basis for the hydro-morphodynamic mechanism of flow convergence routing. This GCS can be evaluated at multiple discharges to reveal hierarchically nested, scale independent landforms that drive fluvial self-maintenance. Several other such dynamic eco-geomorphic mechanisms can be evaluated using GCS analysis. Further, GCS analysis is not only useful to evaluate real rivers, but it also may be used to design reaches to instill hydro-morphodynamic processes requiring sub-reach variability and(or) hierarchically nested, scale-independent landforms. The Python3 open-source software River Builder (free on GitHub) incorporates GCS theory in support of designing complex, organized subreach variability in support for eco-geomorphic processes. This presentation will review eight years of GCS research on a variety of rivers and eco-geomorphic processes as well as demonstrate river design with GCS in River Builder.