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.

5 Apr 2022

Optimization of Reach-Scale Gravel Nourishment on the Green River below Howard Hanson Dam, King County, Washington

Abstract: The US Army Corps of Engineers, Seattle District, nourishes gravel downstream of Howard Hanson Dam (HHD) on the Green River in Washington State. The study team developed numerical models to support the ongoing salmonid habitat improvement mission downstream of HHD. Recent advancements in computing and numerical modeling software make long-term simulations in steep, gravel, cobble, and boulder river environments cost effective. The team calibrated mobile-bed, sediment-transport models for the pre-dam and post-dam periods. The modeling explored geomorphic responses to flow and sediment regime changes associated with HHD construction and operation. The team found that pre-dam conditions were significantly more dynamic than post-dam conditions and may have had lower spawning habitat quality in the project vicinity. The team applied the Bank Stability and Toe Erosion Model to the site and then calibrated to the post-dam gravel augmentation period. The team implemented a new hiding routine in HEC-RAS that improved the simulated grain size trends but underestimated coarse sediment transport. Models without the hiding function overestimated grain size but matched bed elevations and mass flux very well. Decade-long simulations of four future gravel nourishment conditions showed continued sediment storage in the reach. The storage rate was sensitive to nourishment mass and grain size.

4 Apr 2022

Setup and Data Collection Process of an Acoustic Doppler Velocimeter (ADV) in a Laboratory Setting

Abstract: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to outline experimental set up and the data collection process of an Acoustic Doppler Velocimeter (ADV) in a laboratory setting. The Nortek Vectrino ADV will be referenced in this CHETN as will the Nortek Comprehensive Manual for Velocimeters (Nortek AS 2018). Note that Nortek no longer sells the Vectrino, but the Vector, which is similar to the Vectrino aside from only having one configuration, is available.

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.

16 Feb 2022

Walter Marine and Atlantic Reefmaker Wave Attenuator: Wave Transmission Testing Results

Abstract: As part of a testing service agreement with Walter Marine and Atlantic Reefmaker, a 1:5.2 physical model of the Reefmaker Wave Attenuator was constructed and tested by the US Army Engineer Research and Development Center to evaluate its influence on wave attenuation. The tested prototype wave periods ranged from 2.5 to 8 sec with prototype wave heights between 1 ft and 6.5 ft. The Reefmaker Wave Attenuator included orthogonal and square designs and was tested under a variety of configurations including a suspended configuration, a bed-mounted configuration, and a rotated configuration. Testing demonstrated that depending on configurations and wavelength, the wave transmission coefficients ranged from 0.29 to 0.70. The most improvement, however, was demonstrated when testing the square unit designs with transmission coefficients, kt, below 0.51. The smallest kt of 0.29 occurred during square unit testing, which consisted of eight bed-mounted, square Ecosystem disks plus a base unit (24.05 in. freeboard) and with a wave period of 3.0 sec and height of 0.84 ft. Of all 134 tests performed, including the suspended case, the average transmission through the structure was 58%.

15 Feb 2022

Vessel Speed Analysis before and after Dredging near Missouri River Mile 282 in November 2020

Abstract: The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to present information on vessel traffic before, during, and after a dredging event around river mile 282 of the Missouri River in November 2020 along with contextual information about tonnage and commodities that utilize this navigation project.

9 Feb 2022

Implementation of Flexible Vegetation into CSHORE for Modeling Wave Attenuation

Abstract: This technical report presents the new numerical modeling capabilities for simulating wave attenuation and mean water level changes through flexible vegetation such as smooth cordgrass in coastal and marine wetlands. These capabilities were implemented into the Cross-SHORE (CSHORE) numerical model. The biomechanical properties of vegetation such as dimensions, flexibility, and bending strength are parameterized in terms of the scaling law. Correspondingly, a new formulation of the vegetation drag coefficient, CD, is developed using field data from a salt marsh in Terrebonne Bay, LA, by considering spatially varying effective stem and blade heights of species. This report also presents a general procedure for using the model to simulate hydrodynamic variables (i.e., waves, currents, mean water levels) at vegetated coasts, which are used to quantify the effects of wave attenuation and reduction of surge and runup due to vegetation. Preliminary model validation was conducted by simulating a set of laboratory experiments on synthetic vegetation, which mimicked the flexibility of Spartina alterniflora. The validation results indicate that the newly developed vegetation capabilities enable CSHORE to predict changes of wave heights and water levels through marshes by considering species-specific biomechanical features. The model is also applicable to assess vegetation effectiveness against waves and surges.

25 Jan 2022

Freight Fluidity for the Port of Baltimore: Vessel Approach and Maritime Mobility Metrics

Abstract: The United States Army Corps of Engineers is tasked with maintaining waterborne transportation system elements. Understanding channel utilization by vessels informs decisions regarding operations, maintenance, and investments in those elements. Historically, investment decisions have been informed by safety, environmental considerations, and projected economic benefits of alleviating channel restrictions or shipping delays (usually derived from models). However, quantifying causes and impacts of shipping delays based on actual historical vessel location data and then identifying which causes could be ameliorated through investment has been out of reach until recently. In this study, Automatic Identification System vessel position reports were used to develop quantitative measures of transit and dwell-time reliabilities for commercial vessels calling at the Port of Baltimore, Maryland. This port has two deep-water approaches: Chesapeake Bay and the Chesapeake and Delaware Canal. Descriptive metrics were determined for each approach, including port cycle time, harbor stay hours, travel time inbound, and travel time outbound. Then, additional performance measures were calculated: baseline travel time, travel time index, and planning time index. The key finding of this study is that the majority of variability in port cycle time is due to the variability in harbor stay hours, not from channel conditions or channel restrictions.