Beneficial Use of Dredged Material to Mitigate for Erosion

Abstract

The US Army Corps of Engineers (USACE) oversees maintaining waterways, navigation channels, and coastal inlets navigable in the United States and its territories. The USACE dredges approximately 200 to 300 million cubic yards of material annually. Dredged material is being utilized as a beneficial resource for many civil engineering applications (Rakshith & Singh, 2017; Zuliani et al., 2016). The American Society of Civil Engineers (ASCE) recently released Policy statement 349, which is titled Dredged management for erosion control channel maintenance and coastal protection. This policy encourages the use of dredged material for coastal protection and areas that are vulnerable to coastal erosion and might be experiencing environmental degradation or danger to recreational, economic, or commercial activities. Many habitats and water bodies have been impacted by erosion to the extent of either having complete or partial loss of their ecosystem and services. A beneficial use technique that can be implemented with minimal impact to the area being restored is thin layer placement (TLP) of dredged material. This technique could potentially be used for areas that have been impacted by erosion. TLP broadly encompasses the purposeful placement of sediment or dredged material in a manner that produces a specific layer thickness or ground surface elevation necessary to achieving the overall project objectives. In TLP projects, the layer thickness typically ranges from a few centimeters to some fraction of a meter, depending upon the variation in ground surface or water levels at the site, and the functional objectives the placement is intended to achieve. This beneficial use technique could be used for different purposes such as habitat restoration, island creation, marsh restoration, beach nourishment, sediment budgeting, and wetland creation to mitigate for erosion. The US Army Engineer Research and Development Center (ERDC), Dredging Operations Technical Support (DOTS) Program has been providing support for a project, which is a living resource for thin layer placement through the development of a publicly accessible website, providing access to all available resources supporting the planning, design and construction of beneficial use projects employing thin layer placement of dredged material. The website is frequently updated to incorporate new resources, design and modeling tools, and case studies. The site is publicly available; thus, facilitating use of thin layer placement by disseminating information globally and capturing both domestic and international case studies, construction practices and lessons learned. This website serves as a portal to the most readily accessible resources, including literature, available case studies, and external resources, and provides means for users to submit case studies for inclusion on the site. A GIS map-based portal for entry of case studies, placement site and sediment source locations, associated physical and chemical data, hydrodynamics, bathymetry, design drawings, reports and other available information was also developed in conjunction with the website landing pages, providing a geographically oriented information resource for project planning, permitting, design, construction, monitoring, and cost. This website and map-based portal could be used to inform the development of thin layer placement projects to mitigate for erosion.