Large-scale, Two-Dimensional Hydraulic Modeling of a Braided River Using Multi-Resolution Topographic Data

Abstract:

Braided rivers are characterized by anastomosing channels separated by bars and islands and constantly undergo adjustments driven by erosional and depositional processes. Detailed data on the morphology of braided river channels can now be captured at varying scales and spatial resolutions using remote sensing technologies designed for topographic mapping, including interferometric synthetic aperture radar, aerial photogrammetry, and aerial and ground-based lidar. A common product of these data is a digital elevation model (DEM) which not only maps the morphological structure of the river at the time of data acquisition, but also enables analysis of the flow distribution, hydraulic geometry, and bed stresses.

We present a 2D flow model of a 120 km reach of the Platte River, NE, US, parameterized with a 1 m DEM constructed from aerial lidar and channel bathymetry data. The model is motivated by the opportunity to study the flow distribution across threads of different sizes, to examine how braiding changes with increases in discharge, and to study how the distribution of flow among threads evolves with changes in stage. These results shed additional light on the hydraulic geometry of braided rivers. Additionally, the value of fine resolution data is measured by repeating this analysis with coarsened input data.