Challenges with Dredging Impacts
Dredging is commonly undertaken to provide deep enough water for vessels to transit safely into, out of, and around harbors by maintaining the depths of navigation channels and berths. Sediment can consist of different geological types and can become contaminated through the absorption of spilled chemicals and heavy metals in the waterways, creating challenges for the management of dredged material. The more contaminated the sediment is, the more limited the options for management and the costlier management becomes.
Solutions Provided by EEMS
EEMS is commonly used to determine the impacts of dredging in terms of removal of sediment. EFDC is open source so it can be used in cases where a tool such as MIKE 3 cannot. DELFT-3D is another commonly used hydrodynamic model, however it is not linked to a sediment transport model that has the capability to utilize erosion rate data obtained from Sedflume testing (i.e., SEDZLJ capabilities) so is not applicable in many North American applications.
Both of the sediment transport models are internally coupled to a toxics sub-model for simulation of contaminated sediments.
Examples of Studies Done with EEMS
EEMS is being in several studies used to assess the impacts of the deepening and widening of Jacksonville Harbor, a major U.S. port. Jacksonville Harbor Navigation Project will deepen the existing channel to allow for larger vessels to access the Jacksonville Port, thereby reducing transportation costs and providing increased navigational safety while minimizing or avoiding negative impacts to environmental resources. The Jacksonville Harbor feasibility study demonstrated that the partially stratified Lower St. Johns Rivers estuary requires a three-dimensional hydrodynamic model to accurately simulate salinity variations with depth. Now EFDC+ using the Sigma-Zed vertical layering option is being used to evaluate changes in the Lower St Johns River salinity.
Hydrodynamic and Sediment Transport Studies
“Newtown Creek was designated a Superfund National Priority Site in 2010/2011 under the guidance of the USEPA. A complete condition survey, last performed in 1991, was performed in April 2009 by the USACE New York District. Sampling and testing for possible future upland placement will be coordinated with the NYSDEC, NYCDEP and other stakeholders. The entire channel was last dredged in 1951 with the removal of 80,000 cys of material. In the 1950s and 1960s, portions of Dutch Kills and English Kills were dredged. The channel has been subject to various industrial contaminant inputs along the river over the past several decades. As a result, the material to be removed may be too contaminated to dredge and place in approved upland sites. New York City Department of Environmental Protection is the local sponsor. Economic re-development of the area is planned. Coordination with the NYCDEP is maintained.” Source
EFDC is being used extensively in hydrodynamic and sediment transport models that will be applied to Newtown Creek, New York. It is selected due to being open source and being linked to a sediment transport model that has the capability to utilize erosion rate data obtained from Sedflume testing (i.e., SEDZLJ capabilities). Section 4, Modeling Memo 1
A high resolution curvilinear model of the Novato Creek, including basins/floodplain was developed, with masks to represent the levee system, and multiple weir/overflow sections to simulate levee overtopping. This grid was combined with this a coarser domain wide model of the Novato Creek below Hwy 37 and above the tidal mud flats on San Pablo Bay. A suite of practical and self-mitigating alternatives to the flood management system within Novato Creek and its tributaries were modeled. Goals included maintaining and improving the existing level of flood protection, reducing dredging costs and associated impacts, improving the efficiency of flood control operations and maintenance, utilizing and supporting natural processes, and adapting to climate change.
Download Example EE Models
Download an example model and run with the free EEMS Demo Version.