The effects of vegetation on shallow jet stability: an experimental study

Shallow jet, also known as estuarine jet, is crucial for river delta evolution. Existing research focuses on jet flow and its carried sediments, and vegetation effects on the shallow jet are largely elusive. To address this gap, we conducted flow visualization experiments using model plants with varying stem density and submergence ratio. Three different velocities of steady current corresponding to different estuarine Reynolds numbers (ReB) were also tested. Results showed that without vegetation, increasing ReB significantly reduced jet stability and caused large-scale vortices to form at smaller size, higher frequency and closer to the outlet. The presence of vegetation tends to stabilize the shallow jet and shift the thresholds of stability regimes. As the vegetation submergence ratio decreases and stem density increases, the shallow jet stability was further enhanced. Our study demonstrates that vegetation enhances jet stability, which improves our understanding of the evolution of river deltas and informs river diversion restoration projects conducted in vegetated delta floodplains.