| Abstract | Coastal communities are vulnerable to flooding and erosion hazards, and the associated risks are generally escalating, as a consequence of rising sea levels and other factors. It has been widely demonstrated that coastal marsh systems provide ecosystem services in support of coastal resilience and climate change adaptation objectives, in part by acting as buffers against waves and erosion. Recognition of these benefits has led to a growing interest in restoring or constructing coastal salt marshes as part of nature-based solutions for flood and erosion risk management. However, the majority of previous field and experimental studies of wave attenuation and sediment stabilization by salt marsh vegetation has focussed on mature or dense canopies, which are not necessarily representative of conditions in the early stages of a marsh restoration or construction. In this study, a series of full-scale physical model experiments were conducted involving immature Spartina alterniflora vegetation, installed in a laboratory flume in configurations representative of newly constructed or establishing marsh canopies. The response of the live vegetation to irregular waves, was evaluated for various water depth-to-vegetation height ratios, ranging from fully emergent to deeply submerged conditions. Wave attenuation was assessed by measuring wave heights at intervals along the vegetation canopy. The findings will aid practitioners involved in coastal marsh restoration and implementation of nature-based solutions, by providing an improved understanding of wave attenuation by immature Spartina alterniflora canopies, and threshold hydrodynamic conditions for survival of young marsh plants exposed to waves, currents, and a range of water level conditions. This type of information is needed to guide the design of interim or temporary measures to protect shorelines and plants in the period immediately following a marsh construction or restoration, and to support effective integration of marsh vegetation in nature-based solutions for coastal flood and erosion risk management. |
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