Thin layer placement of sediments for restoring ecological function to submerging salt marshes : a quantitative review of scientific literature

Abstract

PURPOSE:The inundation of salt marshes, due in part to sea level rise, can result in elevation loss and a corresponding reduction in marsh ecological function. Several small-scale marsh restoration pilot projects have involved the addition of a thin layer of sediment to offset excessive inundation caused by loss of salt marsh elevation and resulting submergence. However, a comprehensive review, as well as a synthesis of project designs and the effects of sediment additions on ecological function, is lacking. This technical note reviews the impacts of thin layer placement of sediment on salt marsh ecological function and will serve as a resource for salt marsh restoration projects utilizing thin layer placement of sediments.

Sediment Addition Leads to Variable Responses in Temperate Salt Marsh Greenhouse Gas Fluxes During the Growing Season

“…Understanding how these efforts impact fundamental biogeochemical cycles and ecosystem services is key to designing interventions that have positive societal benefits. While TLP has shown promise in boosting elevation which allows vegetation to regrow at comparable densities (Payne et al., 2021; Raposa et al., 2023; Vanzomeren & Piercy, 2020), it remains largely unknown how TLP will impact GHG dynamics of salt marshes. This study helps to fill this knowledge gap and offers insight into how TLP alters GHG, vegetation, and edaphic condition dynamics.…”

Predictions of the Climate Change-Driven Exodus of the Town of Tangier, the Last Offshore Island Fishing Community in Virginia's Chesapeake Bay

“…Intertidal reefs were exploited by Native Americans pre-European colonization as well as by early European settlers as evidenced by shell middens scattered over the Island (Yarrington, 2020). We recommend thin spray dredging, an application of a 10-15 cm thick layer of material on top of existing wetlands to slow inundation by raising the elevation of the wetland and enhance vegetative growth (Ford et al, 1999;Ray, 2007;VanZomeren and Piercy, 2019) at an estimated cost of 5-10,000 USD/ha. Restoring several areas of former uplands on abandoned lands North of the Town as dunes at an estimated cost of 15-30,000 USD/ha, then creating maritime forested uplands behind them on newly elevated land behind the dunes at the cost of 15-50,000 USD/ha would help protect the Town from severe winter storms coming from a more northern direction, known as a Nor'easter in the USA.…”

Building elevation in mangrove communities : use of Regional Sediment Management to increase coastal wetland resilience to sea-level rise

“…For coastal wetlands to exist into the future, soil accretion must match or outpace SLR. Beneficial uses of dredged material such as thin-layer placement (TLP) can build landscape resilience by increasing soil elevation, improving soil fertility, and enhancing vegetation density (DeLaune et al 1990;Croft et al 2006;La Peyre et al 2009;VanZomeren and Piercy 2020).…”

“…Without some intervention, such as TLP, this expansion could increase soil subsidence, ponding, and exacerbation of the effects of coastal storm hazards. Several previous demonstration projects have highlighted the success of TLP in restoration of coastal communities, primarily within salt marshes along the Atlantic coast and Louisiana (DeLaune et al 1990;Croft et al 2006;La Peyre et al 2009;VanZomeren et al 2018;VanZomeren and Piercy 2020). However, there is little information pertaining to the application of TLP within mangrove communities.…”