Numerical simulation of vegetation evolution in compound channels.

Area of Science:

• Environmental science
• Hydrology
• Ecological modeling

Background:

• Understanding vegetation evolution is crucial for biogeographic feedback and ecological restoration.
• Compound channels present complex flow dynamics influencing vegetation patterns.

Purpose of the Study:

• To develop and apply a vegetation evolution model for compound channels based on a velocity threshold.
• To investigate the influence of velocity threshold, initial vegetation, and relative water depth on vegetation coverage and longitudinal dispersion.
• To compare vegetation evolution in compound versus rectangular channels.

Main Methods:

• A vegetation evolution model was developed using a velocity threshold criterion.
• The model incorporated vegetation effects as an equivalent Manning coefficient.
• Two-dimensional shallow water equations were solved to obtain the velocity field.

Main Results:

• The velocity threshold was the primary driver of vegetation evolution.
• Relative water depth and channel type effects were significant only at low velocity thresholds.
• Longitudinal dispersion coefficient increased with vegetation expansion, stabilizing in mature landscapes.
• Decreasing relative water depth and regular initial vegetation distribution enhanced longitudinal dispersion, particularly in compound channels.

Conclusions:

• The velocity threshold model effectively simulates vegetation dynamics in compound channels.
• Initial vegetation distribution patterns critically influence channel hydrodynamics and dispersion.
• Ecological restoration and management strategies should consider flow velocity and vegetation patchiness.