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Application of a two-dimensional hydrodynamic model to the Fraser River Gravel Reach

University of British Columbia

This thesis investigates the potential analytical uses of two-dimensional (2D) models for large braided river systems such as the Fraser River Gravel Reach, which extends from Laidlaw to Mission, B.C., and examines the limitations and advantages of a 2D modeling approach. The 2D depth-averaged model, River2D, was applied to two sections of the gravel reach: a 4.5 km section of the Fraser River at the Agassiz-Rosedale Bridge and an 8.5 km section near the Harrison River confluence and Minto Island. The secondary objective of this work was to characterize the hydraulics in the modeled reaches. River2D was used to examine various gravel extraction scenarios, investigate bank erosion issues, estimate superelevation of the water surface around bends and to determine local depths and velocities for use in habitat delineation and mapping studies. The two sections of the river studied in this thesis have been the focus of several engineering studies by local consultants over the past few years. Some of the recommendations made in those studies to alleviate local flooding risks and erosion concerns were investigated with River2D. The key steps in a typical 2D modeling study were examined in detail beginning with the development of a digital elevation model (DEM) from topographic and bathymetric survey data, which had been previously collected, followed by the development of a River2D model file and model calibration. The most important step in 2D modeling was found to be obtaining an accurate representation of the bed topography. Channel roughness, which is represented by the roughness length, ks, in River2D, was estimated with the surface d₅₀ of the bed material. In this study, River2D has been shown to be technically sound in terms of its hydrodynamic formulation. Further development of this program is recommended to include a morphodynamic module specifically designed to address issues in the gravel reach.

Thesis/Dissertation

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2009-08-06

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http://hdl.handle.net/2429/11926

Civil Engineering

University of British Columbia

UBCV

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