On the role of mangrove root flexibility and porosity in sediment deposition and erosion control.

Mangrove forests are dynamic ecosystems that provide many ecological services in coastal areas. Mangrove decreases erosion through biophysical interactions of aerial roots (pneumatophores) comprised of rigid and flexible branches oscillating in the water. Precise prediction of the morphological evolution for these changes requires an understanding of interactions between root porosity, water flows, and sediment transport. We present rigid cylinders as well as an elastically mounted rigid patch of circular cylinders as simplified flexible mangrove roots to understand the role of porosity and flexibility on the sediment deposition and erosion control. We carried out the force and PIV measurements for the flexible cylinders limited to a transverse oscillation inside a water tunnel at constant velocities. We investigate the effect of the porosity and flexibility on VIV of the patch over a wide range of Reynolds numbers (1000≤Re≤10000). Our preliminary results indicate that the amplitude of response depends on several parameters including Reynolds number, mass ratio, damping ratio, and natural frequency of the system. We discuss the effect of these parameters on the range of synchronization and their implications for the enhancement of sediment deposition and erosion control.