Conservation of mangroves is a promising approach to climate-change mitigation and adaptation of coastal systems. Mangroves are known as “champions” of sequestering soil carbon, ~50 times more effective than tropical forests. Deforestation can create new channels with relatively high-velocity flows due to a significant reduction in drag forces. These flows can enhance removal of soil carbon from the channels. Paradoxically, the presence of these channels contribute to a reduction of flow velocities within the adjacent forest and potentially facilitate sedimentation. In this study, we conducted laboratory experiments using a simplified model of mangrove roots, which were represented by random and emerged cylinder arrays that partially fill the flume in the lateral. Spatial surface  velocities were acquired using optical (PIV) and acoustic (ADV) techniques. Results show flow in the unvegetated region accelerates linearly and reaches mean streamwise velocities (U) over two times the incident velocity. The lateral velocity is ‘relatively high’ (~0.1U) at the leading edge of the vegetation, but with a rapid decay within the vegetation. A strong mass and turbulent kinetic energy transfer from the vegetated area into the main channel was observed. Spatial data suggest the formation of secondary flows in the main channel that contribute to the redistribution of momentum and mass from the bottom and the vegetated region to the free surface. These experiments helped to obtain a better understanding of the impact of channelization of mangrove forests and prevent irreversible impacts.

Primary Presenter: Johann Delgado, Cornell University (jkd78@cornell.edu)

Authors:

Edwin Cowen, Cornell University  (eac20@cornell.edu)