Multidisciplinary quantification of biogeomorphological impacts of living shorelines
Report
Overview
Overview
Abstract
Coastal salt marsh habitats provide extensive ecosystem services, but face increasing natural and anthropogenic pressures. Degradation and loss of sensitive shoreline habitat from these pressures can occur over varied temporal and spatial scales; and, have broad impacts on biogeomorphology, which is the influence of biota on physical landforms. To address resulting impacts on shorelines, a suite of management options exist, including living shorelines, which aim to maintain intertidal habitat and sometimes include structural components, such as sills, to provide additional shoreline protection. Hardened shorelines, such as bulkheads, are intended to keep shoreline positions static and often suffer reduced faunal and floral biodiversity, reduced sediment distribution along and adjacent to the structure, and loss of critical intertidal ecosystem services. Less is known about the varied impacts of living shorelines, but research to date suggests that this form of soft shoreline management often preserves biodiversity and ecosystem habitat. However, there remains a large deficit in knowledge regarding how the presence of sill living shorelines influence biogeomorphological functions, such as how functions are impacted by sea level rise and how significant relative (local) differences in physical characteristics and pressures (e.g., tidal range, fetch, sediment composition, geomorphology) affect the performance of living shorelines. Living shorelines appear to be and are often promoted as mechanisms that improve resilience. This two-year Student Challenge study seeks to address Topic 6 by: quantifying the biogeomorphological impacts of estuarine shoreline stabilization decisions by comparing living shorelines to unaltered, natural control shorelines across multiple spatial and temporal scales. It is critical that we explore the implications of living shorelines on biogeomorphology to justify their installation as forms of restoration and shoreline stabilization, particularly as these projects age; clarifying their relevance as a strategy to build resiliency. Critically, this study will begin to explore if living shorelines are able to keep pace with natural and anthropogenic forcing, such as global climate change and sea level rise, by influencing horizontal and vertical marsh development. Together, these data can show differences in biogeomorphology between living shorelines and unaltered shorelines. It is critical that we begin to explore the biogeomorphological implications of living shorelines to justify their installation as forms of restoration, eco-conscious management, or a shoreline stabilization method; clarifying their relevance compared to hardened shoreline methodology. Sill living shorelines are intended to mimic fringing oyster reefs but are often installed at sites that are naturally soft bottom habitat. A greater understanding of the impacts of sill-based living shorelines is particularly important, as the installation of a higher elevation hard substrate results in a loss of soft bottom subtidal habitat, naturally found in North Carolina and southeastern estuaries (Currin, Delano, Valdes-Weaver, 2007). Due to this, this study proposes to include both soft bottom and natural fringing oyster unaltered control sites. Critically, this study will begin to answer if and how sill-living shorelines impact the biogeomorphology of a shoreline and explore if living shorelines are able to keep pace with natural and anthropogenic forcing, such as global climate change and sea level rise, by influencing horizontal and vertical accretion.
