Hydraulics & Waterways

Oral

387869 - Are mangroves as tough as a seawall? Flow-vegetation interaction in a living shoreline restoration

Wednesday, June 6
10:30 AM - 12:00 PM
Location: Regency Room
Co-Authors: Vasileios Kitsikoudis, Orlando, Florida – University of Central Florida; David Spiering, Orlando, Florida – University of Central Florida

This study assesses the impact of an established living shoreline restoration to near-shore hydrodynamics, sediment texture, and organic matter content. We collected data from three estuarine shorelines: one restored; one eroding and stabilized by a seawall; and one in reference condition stabilized by mature mangrove vegetation. The living shoreline site was restored six years prior with a breakwater of oyster reef and plantings of emergent marsh grasses and mangroves. We sampled incoming velocity profiles of the full water column with a 2 MHz Acoustic Doppler Current Profiler (Nortek) approximately 10 m offshore. A near-bed velocity profile was simultaneously sampled on the shoreline at 100 Hz, using a Nortek Vectrino profiler. The onshore probe was placed within vegetation in restored and reference sites (respectively N = 60 and 49 stems/m^2 and solid volume fraction φ=0.006 and 0.027). Hydrodynamic gradients from offshore to onshore reflect attenuation by vegetation; onshore velocities in restored and reference sites were orders of magnitude lower than offshore. Onshore velocities at the seawall site were similar in magnitude to offshore. Near-bed shear stress gradients were likewise flat in the seawall site and increased as water flowed through vegetation in the restored site. However, shear stresses did not increase through the mangrove prop roots at the reference site. The variable shear stress patterns observed at restored and reference sites likely attribute to differences in dominant vegetation-water interactions, mediated by stem density and plant morphologies. Sediment grain sizes in the reference site were finer and contained more organic matter.

Kelly Kibler


University of Central Florida

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387869 - Are mangroves as tough as a seawall? Flow-vegetation interaction in a living shoreline restoration



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