SRH-Meander (Formerly GSTAR-M)
A numerical channel migration model has been developed for meandering rivers to predict the future river channel alignment (Randle, 2004).
The model is based on:
- 1. A new equation to predict the rate of bank erosion; and
- Use of the minimum unit stream power hypothesis (minimum VS) to determine the planform –phase-lag between the changing curvature of the river channel and the changing curvature of the flow.
The model predicts channel migration as a function of river discharge, sediment transport capacity, channel radius of curvature, channel width, hydraulic depth, and the bank material properties of the river channel including vegetation, large woody debris, cohesion, and armoring. The model can simulate the migration of tens of river miles, over a period of decades using daily or hourly variations in flow. Each model simulation can be completed in a period of minutes so that a wide range of hydrology could be individually simulated.
The model assumes that the river evolves naturally to be capable of transporting the upstream sediment load through a reach without erosion or deposition along the channel bed. The model therefore continually adjusts the channel width, depth, and slope (through the meandering alignment) so that the local sediment transport capacity matches the upstream sediment supply. The model assumes that sediment input from bank erosion is on average balanced by sediment deposition through point bar accretion. At this time, the model cannot be used to simulate channel aggradation or degradation.
The migration of river channels across their floodplains and the occasional erosion of terrace banks are natural processes. These processes become especially important to people living in or near the floodplain or to organizations planning or maintaining infrastructure within or along the edge of the floodplain. Natural rates of channel migration can be accelerated, reduced or negated by human disturbance. For example, the clearing of native floodplain vegetation can accelerate the rate of channel migration, while the placement of rip rap or other bank protection can limit or even prevent channel migration.
The channel migration model predicts the future alignment of meandering river channels. The model could be used as a planning tool to evaluate the effects of alternate patterns of water releases downstream from dams and alternative land management practices. For example, the effects of varying the annual peak river flows on the rate and extent of channel migration can be evaluated. In addition, the effects of removing bank protection along selected reaches to promote channel migration can be evaluated.