DSI is currently providing technical services to Jacobs in support of the implementation of the Remedial Design (RD) for Portland Harbor. We are supplying specialist modeling services to develop the B1a Project Area Basis of Design Report (BODR). The report requires the simulation of several flooding scenarios, including the 1996 Flood Event, and using the…
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The St. Johns River (SJR) flows north, from its headwaters in the marshes of Indian River County, to the Atlantic Ocean near Jacksonville. The lower St. Johns River (LSJR) is defined as the portion of the river that extends from the confluence of the St. Johns and Ocklawaha rivers near Welaka north to the mouth of the SJR at Mayport in Jacksonville; the LSJR is about 120 miles in length. Tidal marshes surround the lower part of the estuary, where the river is mostly channelized due to urban development around Jacksonville, Florida (riverine segment). The LSJR estuary is dominated by wetlands (greater than 50 percent of the floodplain area), which host a diverse range of ecological communities. Both the composition and structure of these wetlands exhibit a strong geographical pattern corresponding to gradients in tidal amplitude, salinity, and soil texture and composition.
The purpose of this study was to evaluate potential impacts on the aquatic habitat of salinity intrusion into the estuary, and create a basis for evaluating multiple management scenarios to support decision-making.
Lower St. Johns Estuary
The EFDC+ hydrodynamic and salinity model was used to model the LSJR estuary. Five separate simulation periods were used for model calibration and validation. Data collected by USACE, NOAA, USGS, and the SJR Water Management District were used to calibrate the EFDC+ model for water surface elevation and salinity. Following model calibration, an 8.5-year Production Run (PRP) from January 2008 to June 2016 was run to evaluate the long-term trends in salinity intrusion and analyze the long-term behavior of the estuary in relation to salinity stress on locations in the estuary with submerged aquatic vegetation beds (SAV) and wetlands.
A habitat analysis of submerged aquatic vegetation and wetlands was performed, which serves as a baseline for comparison with alternative management and future change scenarios for the basin.
The final model and the modeling report were submitted to the client to be used in developing and evaluating additional management scenarios.
Visualizing Salinity Change in Lower St Johns River.
The Willamette River originates in the Cascade Mountain Range, flowing through northwestern Oregon for 187 miles to its confluence with the Columbia River. The final 26.5-mile stretch of river downstream of Willamette Falls before the Columbia River confluence is considered the Lower Willamette River. It is a slow-moving, tidally influenced segment that experiences intermittent reverse flow at high tide during the low flow season (usually summer and early fall). Portland Harbor is defined as the 9.9-mile dredged reach of the Lower Willamette River between River Miles 1.9 and 11.8. The harbor is surrounded by light and heavy industry and mixed commercial and residential development around the City of Portland. A variety of industrial activities historically occurred and continue to take place around the harbor, including marine shipping terminals, bulk fuel facilities, manufacturing, and other commercial operations. In 2000, USEPA placed the Portland Harbor Superfund site on a National Priorities list (NPL).
Develop a scientifically defensible model to simulate the hydrodynamic and sediment erosion and transport processes in Portland Harbor to support contaminate source identification and cleanup cost allocation.
DSI developed a hydrologic model of City of Portland private and public drainages, loosely coupled with multi-scale hydrodynamic and sediment transport models of the Lower Willamette and Columbia Rivers. The multi-scale hydrodynamic models included a large-scale, coarse grid model for the entire domain and nested, fine grid, high-resolution models for individual sediment management areas (SMAs). This modeling system coupled the simulation of the large-scale hydrodynamic and sediment transport processes of the site with the ability to provide model predictions on the scale of individual SMAs. The system included fully coupled morphologic feedback of hydrodynamics and sediment bed elevation changes between the models to address existing conditions and future mitigation exports.
DSI submitted the final model and the modeling report to the model sponsors to support remedial design, recovery monitoring, and the cleanup cost allocation process.
Alberta Environment and Parks (AEP) has developed a South Saskatchewan Region Plan (SSRP) to flexibly and proactively manage the cumulative effects of human activity on surface water quality within the South Saskatchewan Region. Scientific models used to evaluate the effectiveness of various management and engineering environmental options have been a key component of the management approach. As part of SSRP, AEP commissioned an in-stream water quality model for the Little Bow River.
The Little Bow River watershed is located in the headwaters of the Oldman River Basin in the southern region of the Province of Alberta. As a major tributary of the Oldman River, the Little Bow River receives diverted flows from the Highwood River, direct precipitation, local runoff, and municipal/industrial discharges. The Upper Little Bow River Basin occupies an area of approximately 3,491 km$^2$, and supports a wide variety of natural resources, including forests, minerals, wildlife, and agricultural lands.
The project goal was to develop a hydrodynamic and water quality model of the Little Bow River as an assessment tool to support flood mitigation work related to the Highwood-Little Bow diversion system and Little Bow River.
Little Bow River Watershed
Using Environmental Fluid Dynamics Code Plus (EFDC+), DSI developed a two-dimensional (2D) and three-dimensional (3D) model of the Little Bow River, which extended about 165 km and included an in-stream reservoir (Twin Valley), and a 55 km tributary (Mosquito Creek). The reaches were represented by 2D grids and the reservoir was represented using 3D grids. The model boundary condition inputs were provided using monitoring data and a watershed model developed using Soil and Water Assessment Tool (SWAT).
The model simulated hydrodynamics, temperature, ice, dissolved oxygen, nutrients, macrophytes, algae, and the processes involved in the complete nutrient cycle. Following the calibration of the model for all physical, chemical, and biological parameters, DSI used the calibrated model of the complete system to evaluate multiple management scenarios, including flow diversion at Highwood, reservoir operations, and Waste Water Treatment Plant (WWTP) effluent water quality control.
DSI submitted the complete model and the final report to AEP and provided training to agency staff. AEP uses the model for management scenario evaluation.
This video demonstrates how the Little Bow River WQ simulation helps better understand and manage water resources.
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