Modeling One and Two Dimensional Evolution of Straight Channels after Dam Removal
Date Issued
2014
Date
2014
Author(s)
Chu, Chia-Chu
Abstract
This study tries to use the Exner equation to investigate the one dimensional and horizontal two dimensional channel evolution after removal of a dam. The Exner equation considers the difference of sediment transport rate in space to govern the channel evolution. In 1D condition, by assuming uniform flow, no incipient shear stress, and constant flow rate, the Exner equation can be derived as a diffusion equation. In this study, this equation is solved analytically by Fourier transformation method. On the other hand, the Exner equation under a horizontal 2D straight, inerodible banks, and no secondary flow channel can be derived as our governing equation which has the nonlinear terms, and the analytical method might not work to solve the Exner equation under the 2D condition. Hence, we adopt the finite difference method to proceed this work. The result of 1D analytical solution represents that the flushing rate is decreasing as time goes by, and reveals the sediment transport rate is significant in the early stage of the dam removal. On the other hand, the 2D results represent that under our assumptions, the sediment will transport to the center of the channel to become very similar to the 1D phase. In summary, the 1D channel evolution is dominated by the diffusivity which is a function of flow rate, and the 2D channel is dominated by the relationship between sediment and water. Thus, the hydrology condition might be the main factor to control the channel evolution.
Subjects
Removal of a dam
Channel evolution
Straight channel
Exner equation
Diffusion equation
Type
thesis
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