19 Aug 2022

The Old River, Mississippi River, Atchafalaya River, and Red River (OMAR) Technical Assessment

NOTE: The Old River, Mississippi River, Atchafalaya River, and Red River (OMAR) Technical Assessment is a 9-volume series of reports that was produced under the direction of the Mississippi River Geomorphology & Potamology Program. An abstract from the main report, Volume 1, is listed below, along with the individual volume titles and links to the relevant reports. ABSTRACT: This is the main report of Old River, Mississippi River, Atchafalaya River, and Red River (OMAR) Technical Assessment. The primary objective of the OMAR Technical Assessment was to conduct a comprehensive evaluation that aimed to understand the impacts of former and potential changes to the system in the vicinity of the Old River Control Complex (ORCC) over time, the water and sediment delivery regime at the ORCC, and the effects to the river system surrounding the ORCC. Scenarios evaluated in this technical assessment were designed to investigate potential system responses to a wide range of possible operational alternatives and identify knowledge gaps in current understanding of system behavior. This report summarizes and synthesizes the individual reports detailing the investigations into specific aspects of the ORCC and the surrounding region.

4 Aug 2022

Supporting Bank and Near-bank Stabilization and Habitat Using Dredged Sediment: Documenting Best Practices

Abstract: In-water beneficial use of dredged sediment provides the US Army Corps of Engineers (USACE) the opportunity to increase beneficial use while controlling costs. Beneficial use projects in riverine environments include bank and near-bank placement, where sediments can protect against bank erosion and support habitat diversity. While bank and near-bank placement of navigation dredged sediment to support river-bank stabilization and habitat is currently practiced, documented examples are sparse. Documenting successful projects can support advancing the practice across USACE. In addition, documentation identifies data gaps required to develop engineering and ecosystem restoration guidance using navigation-dredged sediment. This report documents five USACE and international case studies that successfully applied these practices: Ephemeral Island Creation on the Upper Mississippi River; Gravel Island Creation on the Danube River; Gravel Bar Creation on the Tombigbee River; Wetland Habitat Restoration on the Sacramento-San Joaquin River Delta; and Island and Wetland Creation on the Lower Columbia River Estuary. Increased bank and near-bank placement can have multiple benefits, including reduced dredge volumes that would otherwise increase as banks erode, improved sustainable dredged sediment management strategies, expanded ecosystem restoration opportunities, and improved flood risk management. Data collected from site monitoring can be applied to support development of USACE engineering and ecosystem restoration guidance.

29 Jul 2022

Investigation of Sources of Sediment Associated with Deposition in the Calcasieu Ship Channel

Abstract: The Calcasieu Ship Channel (CSC) is a deep-draft federal channel located in southwest Louisiana. It is the channelized lowermost segment of the Calcasieu River, connecting Lake Charles to the Gulf of Mexico. With support from the Regional Sediment Management Program, the US Army Corps of Engineers, New Orleans District, requested that the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, perform an investigation of the potential sources of sediment associated with dredging in the CSC. A previous study had quantified sediment from known sources, indicating that the known sediment sources contribute approximately only 21% of the volume that is regularly dredged from the channel. This technical report details the results of the current study, which employed multiple methods, including numerical analysis, to identify potential additional sources of sediment by first examining the available literature and the modeled energetics and flow pathways, and then estimating the quantities of sediment associated with these identified sources that may be contributing to the shoaling of the CSC. The results of these efforts were used to update the original sediment budget with estimates of the contributions from two additional sources: the erosion of interior wetlands and coastally derived sediments.

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

20 Jul 2022

Impacts of Granular Activated Carbon (GAC) on Erosion Behavior of Muddy Sediment

Abstract: Recent policy changes regarding the placement of dredged material have encouraged the USACE to increase its beneficial use (BU) of the sediments dredged from the nation’s navigation channels. A good portion of this material is fine grained (<63 mm), which traditionally has limited use in BU applications, in part due to its dispersive nature. A need exists to evaluate the potential of stabilizing and using fine-grained sediment (FGS) in BU projects. Previous studies have shown the addition of granular sand to FGS reduces the mobility of the bed. The potential of using Granular Activated Carbon (GAC), an amendment commonly used in environmental capping involving FGS, as a similar bed stabilizing material was explored in this study. A series of laboratory erosion tests using Sedflume were performed on FGS-GAC mixtures that ranged from 5% to 20% GAC by mass. Results suggested that GAC content ≤10% had no influence on the stability of the bed while GAC content ≥15% appeared to reduce both critical shear stress (τcr) and erosion rate (n). However, when compared to control cores, those without GAC, clear evidence of bed stabilization of FGS from the addition of GAC was not observed.

16 Jun 2022

Development of a Two-Dimensional HEC-RAS Sediment Model for the Chippewa River, Wisconsin, for Software Development and Sediment Trend Analysis

Abstract: This US Army Corps of Engineers (USACE) Regional Sediment Management technical note (RSM-TN) describes an RSM effort that converted a one-dimensional (1D) sediment transport model of the Chippewa River confluence with the Mississippi River into a two-dimensional (2D) model. This work leveraged recent sediment data collection and tested the new 2D sediment transport capabilities in the Hydrologic Engineering Center, River Analysis System (HEC-RAS) Version 6.0. In addition to the benefits of software testing, the resulting model developed through this effort can provide more accurate spatial and temporal information about sedimentation in the Mississippi River navigation channel and help inform future dredging strategies for the St. Paul District, USACE.

15 Apr 2022

South Shore of Long Island, New York Regional Sediment Management Investigation: An Overview of Challenges and Opportunities

Abstract: The US Army Corps of Engineers (USACE) is conducting the “South Shore of Long Island, New York Regional Sediment Management Investigation” to further understand sediment dynamics and to develop a comprehensive regional sediment management plan for the south shore of Long Island, New York. Regional sediment management is a systems approach using best management practices for more efficient and effective use of sediments in coastal, estuarine, and inland environments. This investigation seeks to characterize sediment movement on the south shore of Long Island as a holistic system across the entire study area. It focuses on the regional system post-Hurricane Sandy (October 2012) as the storm significantly altered the physical landscape with severe shoreline erosion, which resulted in the construction of projects to reduce the risk of future storms and stakeholder priorities with a new emphasis on bay-side sediment dynamics, such as channel shoaling and disappearing wetlands. Despite the fact the storm caused severe erosion, the equilibrium beach profile, depth of closure, and general shoreline orientation seem to be unaffected. Previous studies have characterized sediment movement at specific sections of the south shore, but these data have not been incorporated to create a system-wide perspective. Coordinating sediment management across the six Atlantic Ocean inlets, Great South Bay Channel, Intracoastal Waterway, and coastal storm risk management (CSRM) projects could save the federal government millions of dollars in dredging and sand placement actions. This technical note presents the progress the investigation has made to date and will be followed with a more in-depth technical report titled South Shore of Long Island, New York Regional Sediment Management Investigation: A Post-Hurricane Sandy Shoreline Evaluation, currently in preparation.

14 Apr 2022

Tombigbee River: River Miles 81.0–76.0 Sediment Management Study

Abstract: The US Army Corps of Engineers, St. Louis District, Applied River Engineering Center (AREC), in cooperation with the Operations Branch of the Mobile District, conducted a sediment management study of the Sunflower Bend reach of the Tombigbee River, between River Miles 81.0 and 76.0, near Jackson, AL. The objective of the study was to look at sediment management alternatives to alleviate or eliminate repetitive maintenance dredging. These alternatives involved various river engineering measures including dikes, weirs, channel armoring, disposal armoring, and combinations thereof. A physical Hydraulic Sediment Response model was used to examine the sediment response resulting from these alternatives. During model testing, and after discussions with AREC and Mobile Operations Division staff, a second objective was established to define existing non-erodible bed materials that were located throughout the reach. This was conducted to examine the merits of strategically removing these erosion resistant materials in the river as an additional dredging/excavation alternative. The most favorable alternatives involved removing bedload sand and consolidated clay material from between River Miles 79.1 and 78.0 to improve navigation.

29 Mar 2022

Evaluating Cross-Shore Sediment Grain Size Distribution, Sediment Transport, and Morphological Evolution of a Nearshore Berm at Fort Myers Beach, Florida

Abstract: Navigation channels are periodically dredged to maintain safe depths. Dredged sediment was historically placed in upland management areas or in offshore disposal areas. Florida state law prohibits placement of beach fill sediment that contains more than 10% by weight of silt and clay, which is typically a characteristic of dredged material. An alternative is placement in a nearshore berm. Some potential benefits of nearshore berms include wave energy dissipation, reduced cost of dredging and shore protection, and possible onshore movement of the berm material. This study considers sediment distribution, morphological evolution, sediment transport, and shoreline trends along Fort Myers Beach, Florida, related to the nearshore berm constructed in August 2016. Due to timing of the field study, this report also includes information on the influence of a major hurricane that impacted the area. The overall conclusion of this study is that the dredge-sourced sediment in the berm performed as expected. Within 2 years, the berm adjusted to the shoreface environment, maintained a large part of its original volume, and contributed to protection of the beach and shoreline. The impact of Hurricane Irma included a shift in sediment textures and a large but temporary increase in shoreface sediment volumes.

2 Mar 2022

Wabash and Ohio River Confluence Hydraulic and Sediment Transport Model Investigation: A Report for US Army Corps of Engineers, Louisville District

Abstract: Avulsions of the Wabash River in 2008 through 2011 at its confluence with the Ohio River resulted in significant shoaling in the Ohio River. This caused a re-alignment of the navigation channel and the need for frequent dredging. A two-dimensional numerical hydrodynamic model, Adaptive Hydraulics (AdH), was developed to simulate base (existing) conditions and then altered to simulate multiple alternative scenarios to address these sediment issues. The study was conducted in two phases, Phase 1 in 2013 – 2015 and Phase 2 in 2018 – 2020. Field data were collected and consisted of multi-beam bathymetric elevations, bed sediment samples, suspended sediment samples, and discharge and velocity measurements. The model hydrodynamic and sediment transport computations adequately replicated the water surface slope, flow splits, bed sediment gradations, and suspended sediment concentrations when compared with field data. Thus, it was shown to be dependable as a predictive tool. The alternative that produced the most desirable results included a combination of three level-crested emergent dikes on Wabash Island and four submerged dikes on the Illinois shore with a level crest from the bank to the tip of the dike. The selected alternative produced an improved sailing line while maintaining authorized channel depths.