11 Aug 2023

Dredged Material Can Benefit Submerged Aquatic Vegetation (SAV) Habitats

Purpose: This technical note (TN) was developed by the US Army Engineer Research and Development Center–Environmental Laboratory (ERDC-EL) to provide an overview of the ecosystem services delivered by submerged aquatic vegetation (SAV) to estuarine and coastal ecosystems and to describe potential methods for the beneficial use of dredged material (BUDM) to aid in SAV restoration. Although dredging tends to have a negative association with SAV habitats, BUDM may provide an opportunity to expand suitable SAV habitat to areas where depth is the primary limiting factor. Recent in situ observations have shown that SAV has opportunistically colonized several dredged-material placement sites. This TN provides context on BUDM for SAV habitat restoration to encourage increased strategic placement.

24 Jan 2023

Swan Island Resilience Model Development; Phase I: Conceptual Model

Abstract: This report documents the development of an integrated hydrodynamic and ecological model to test assumptions about island resilience. Swan Island, a 25-acre island in Chesapeake Bay, Maryland, was used as a case study. An interagency, interdisciplinary team of scientists and engineers came together in a series of workshops to develop a simplified resilience model to examine the ability of islands to reduce waves and erosion and the impacts to nearby habitats and shorelines. This report describes the model development process and the results from this first key step: model conceptualization. The final conceptual model identifies four main components: vegetative biomass, island elevation, waves/currents, and sediment supply. These components interact to form and support specific habitat types occurring on the island: coastal dunes, high marsh, low marsh, and submerged aquatic vegetation. The pre-and post-construction field data, coupled with hydrodynamic ecological models, will provide predictive capabilities of island resilience and evaluations of accrued benefits for future island creation and restoration projects. The process and methods described can be applied to island projects in a variety of regions and geographic scales.

13 Sep 2022

Sediment Mobility, Closure Depth, and the Littoral System – Oregon and Washington Coast

Abstract: Forty years ago, the depth of closure concept was introduced to provide a systematic, process-based approach to evaluate seasonal changes in cross-shore profiles and sediment mobility in the nearshore. This study aims to extend that theory by directly considering wave-asymmetry in the nearshore environment. This technical note introduces a methodology to calculate wave induced dispersal of dredged material placed in nearshore sites and summarizes analyses validating the approach using data from the South Jetty Site at the Mouth of the Columbia River. This investigation highlights the notion of a cross-shore gradient in nearshore placement effectiveness of dredged material that can assist project managers plan and execute sustainable sediment management practices at coastal inlets.

12 Sep 2022

Application of Clean Dredged Material to Facilitate Contaminated Sediment Source Control

Abstract: Navigation channels, turning basins, and other US Army Corps of Engineers (USACE)–managed navigation infrastructure often serve as repositories for contaminated sediment from off-site sources. As much as 10% of the material that USACE dredges on an annual basis is contaminated such that it requires additional and more costly management (for example, rehandling and placement in managed confined disposal facilities). Presence of contaminated sediments constrain potential management options resulting in additional costs and opportunity loss from the inability to beneficially use the material. One potential solution is applying clean dredged material to stabilize and isolate contaminated sediment sources, preventing further transport and introduction to USACE-managed infrastructure. This document summarizes a comprehensive literature review of laboratory and field case studies relevant to using clean dredged material to isolate or stabilize contaminated sediments, focusing on the physical, chemical, and biological parameters critical to establishing its feasibility and long-term effectiveness. Potentially effective engineering control measures were also reviewed where erosion and site hydrodynamics are facilitating the transport of contaminated sediments to USACE-maintained navigation infrastructure. This literature review documents and summarizes those factors considered in establishing feasibility and long-term effectiveness of the approach as well as the applicable engineering tools employed and constraints encountered.

31 Aug 2022

Current State of Practice of Nearshore Nourishment by the United States Army Corps of Engineers

Abstract: This US Army Corps of Engineers (USACE) special report prepared by the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, provides an overview of the current state of practice for nearshore nourishment with dredged sediment. This special report was completed with responses and input from professionals across the dredging and placement teams from each of the USACE Coastal and Great Lakes districts, providing comprehensive overviews of the decision trees these districts utilize in the placement of their dredged sediment. This report describes the general practice of nearshore nourishment, the impediments and concerns faced by nearshore nourishment projects, and the practical methods utilized by the Coastal and Great Lakes districts for their nearshore nourishment projects. Understanding the current state of practice, along with the general and specific impediments the districts face, enables further research in and development of best practices for use across the USACE and better communication of the practice to other stakeholders.

12 Aug 2022

Swan Island: Monitoring and Adaptive Management Plan

Abstract: Swan Island is a 10.12 ha island located in the Maryland waters of the Chesapeake Bay. Because of its value as a natural wave break for the town of Ewell on nearby Smith Island, as well as the ongoing erosion and subsidence of the island, in 2019 US Army Corps of Engineers (USACE)–Baltimore District placed 45,873 m³ of dredged sediment and planted 200,000 marsh plants. This restoration provided an opportunity to quantify the engineering (that is, resilience) and ecological performance of the island, postplacement. The lack of quantitative data on the performance of natural features such as islands has led to perceived uncertainties that are often cited as barriers to implementation. To address these data gaps, a multidisciplinary collaboration of five government entities identified project objectives and monitoring parameters through a series of mediated workshops and then developed a conceptual model to articulate those parameters and the linkages between them. This monitoring and adaptive management plan (MAMP) documents those monitoring parameters and procedures and can serve as an example for other scales, regions, and research questions. Documenting research and monitoring efforts may help to foster widespread acceptance of nature-based solutions such as islands.

29 Jul 2022

Sediment Provenance Studies of the Calcasieu Ship Channel, Louisiana

Abstract: To maintain the navigability of the Calcasieu Ship Channel (CSC), the US Army Corps of Engineers annually dredges millions of cubic yards of sediment from the inland channel. To assess sources of channel shoaling, a previous study examined river and bankline erosion as inputs. Results from that study accounted for approximately 20% of dredged volumes. Through the support of the Regional Sediment Management Program, a follow-up investigation reviewed prior sediment budgets, identified potential missing sediment sources, modeled potential sediment pathways, and utilized geochemical fingerprinting to discern primary shoaling sources to the channel. The missing sediment sources from the original budget include coastally derived sediment from the Gulf of Mexico and terrestrially derived sediment from Lake Calcasieu and surrounding wetlands. Results from geochemical fingerprinting of various potential sediment sources indicate the Calcasieu River and the Gulf of Mexico are primary contributors of sediment to the CSC, and sediments sourced from bankline erosion, Lake Calcasieu bed, and interior wetlands are secondary in nature. These results suggest that engineering solutions to control shoaling in the CSC should be focused on sources originating from the Gulf of Mexico and river headwaters as opposed to Lake Calcasieu, channel banklines, and surrounding wetlands

11 Jul 2022

USACE Navigation Sediment Placement: An RSM Program Database (1998 – 2019)

Abstract: This US Army Corps of Engineers, Regional Sediment Management, technical note describes a geodatabase of federal coastal and inland navigation projects developed to determine the extent to which RSM goals have been implemented across the USACE at the project and district levels. The effort 1) quantified the volume of sediment dredged from federal navigation channels by both contract and USACE-owned dredges and 2) identified the placement type and whether sediment was placed beneficially. The majority of the dredging data used to populate the geodatabase were based on the USACE Dredging Information System DIS database, but when available, the geodatabase was expanded to include more detailed USACE district-specific data that were not included in the DIS database. Two datasets were developed in this study: the National Dataset and the District-Specific and Quality-Checked Dataset. The National Dataset is based on statistics extracted from the combined DIS Contract and Government Plant data. This database is a largely unedited database that combined two available USACE datasets. Due to varying degrees of data completeness in these two datasets, this study undertook a data refinement process to improve the information. This was done through interviews with the districts, literature search, and the inclusion of additional district-specific data provided by individual districts that often represent more detailed information on dredging activities. The District-Specific and Quality-Checked Database represents a customized database generated by this study. An interactive web-based tool was developed that accesses both datasets and displays them on a national map that can be viewed at the district or project scale

11 Jul 2022

National Sediment Placement Data Viewer Users Guide

Purpose: This US Army Corps of Engineers (USACE) Regional Sediment Management (RSM) technical note serves as a user’s guide for the RSM National Sediment Placement Data Viewer. This application was created utilizing over 20 yr* of detailed and verified USACE dredging data, giving users an interactive web-based tool that takes these datasets and displays them on a national map, viewable at the district or project scale. The Data Viewer will quantify the total cubic yards dredged, disposed, and/or beneficially used based on the user selected parameters. Detailed information on the datasets utilized and the verification processes followed to create this application can be found in ERDC/TN RSM-22-4, USACE Navigation Sediment Placement: An RSM Program Database (1998 – 2019) (Elko et al. 2022). This technical note attempts to define each of the inputs/outputs given from the Data Viewer and then provide a step-by-step example of utilizing the Data Viewer, accessed here: https://www.arcgis.com/apps/MapSeries/index.html?appid=0ea8fc0a956f46068428c862e7497233

28 Jun 2022

Two Years of Post-Project Monitoring of a Navigation Solution in a Dynamic Coastal Environment, Smith Island, Maryland

Abstract: In 2018, jetties and a sill were constructed by the US Army Corps of Engineers adjacent to the Sheep Pen Gut Federal Channel at Rhodes Point, Smith Island, Maryland. These navigation improvements were constructed under Section 107 of the Continuing Authorities Program. Material dredged for construction of the structures and realignment of the channel were used to restore degraded marsh. Following construction and dredging, 2 years of monitoring were performed to evaluate the performance of navigation improvements with respect to the prevention of shoaling within the channel, shoreline changes, and impacts to submerged aquatic vegetation (SAV). Technical Report ERDC/CHL TR-20-14 describes the first year of post-project monitoring and the methodologies employed. This report describes conclusions derived from 2 years of monitoring. While the navigation improvements are largely preventing the channel from infilling, shoaling within is occurring at rates higher than expected. The placement site appears stable and accreting landward; however, there continues to be erosion along the shoreline and through the gaps in the breakwaters. SAV monitoring indicates that SAV is not present in the project footprint, even though turbidity is comparable to the reference area. Physical disturbance of the bottom sediment during construction may explain SAV absence.