Mitigating Erosional Effects Induced by Boat Wakes with Living Shorelines

Abstract

Estuarine environments worldwide are among the most threatened habitats due to increased disturbances resulting from coastal infrastructure and rising population densities. Boating activity is a primary disturbance, as it induces biological stress and morphological changes along the coastline. This high-energy environment that boat wakes create has resulted in loss of surrounding oyster reefs and salt marsh vegetation, ultimately leading to shoreline and habitat erosion. Here, we characterize the boat wake climate in the Intracoastal Waterway, assess the bathymetry in this heavily trafficked area, and anticipate the effects of experimental living shorelines (natural breakwall and oyster restoration structures) on facilitating sediment deposition and slowing vegetation retreat. Field observations indicate that boat wakes suspend nearshore sediment and can reach heights greater than 40 cm. A numerical stability model of the breakwalls suggests that the optimal porosity is field-specific. The desired porosity for minimizing lateral displacement is 0.50, while it is 0.18 for maximum energy dissipation, which indicates a need to further investigate this complex problem. These findings demonstrate that boat wakes significantly and regularly disturb estuarine shorelines and may be altering their bathymetry as well as suggest that the design of the breakwalls may be optimized to best counteract this pervasive disturbance.

Mimicry of emergent traits amplifies coastal restoration success

“…At present, erosion is an increasing problem along coastlines in general, and at degraded sites that require restoration in particular 36 . To combat this pervasive challenge, hard structures from shells or concrete are often applied to provide stable substrates necessary to stimulate reef formation [37][38][39][40][41][42][43] , while sediment stabilization measures have been used to support vegetation establishment 44,45 . Our approach builds upon these efforts by experimentally demonstrating that tailor-made mimicry of species-specific key emergent traits-identified from past ecological studies-facilitates the establishment of different habitat-forming species.…”

“…In engineering design, such a complex problem is often approached using a morphological analysis that allows exploration of all possible solutions for the combinations of functions one aims to achieve 60 . For restoration, morphological analysis may help design structures that simultaneously ameliorate multiple emergent trait-mitigated bottlenecks, such as wave attenuation combined with sediment stabilization by coastal vegetation 38,61 , or provisioning of attachment substrate combined with predation shelter by oysters and mussels 28,38,[62][63][64][65][66][67] .…”

After Hurricanes Irma and Matthew: Living Shorelines Stabilize Sediments

“…35 Sediment cores (22 cm depth; 7 cm diameter) were collected with a push corer before and after the storms to compare the sediment profiles and determine if the sediment had become disturbed due to these storms. Before the storms, in June 2016, one sediment core was taken from behind/landward each of three oyster reefs (2,17,21) and at three control sites, where no reefs were present (Figure 1). Post-storms, in December 2017, sediment cores were collected from behind three different reefs (15,16,18).…”

Boating- and Shipping-Related Environmental Impacts and Example Management Measures: A Review

“…Thrust fields from propellers and wash/depression waves from moving vessels potentially result in resuspending bottom sediments and physically impacting benthic and shoreline communities and habitat through bank and bed erosion [91][92][93][94][95]. Bottom resuspension may result from thrust fields from vessel propellers or solitary long waves that cause increased water velocities inducing resuspension.…”