Portland Harbor B1a 30% Design Support

Introduction

Portland Harbor, located along the lower Willamette River in Oregon, is an EPA-designated Superfund site. DSI has previously developed several numerical models of this region to support evaluations of toxic transport and sediment dynamics. In this project, DSI built upon the model validated with the latest ADCP data and tested the model under different client-specified design conditions.

Project Goal

The purpose of this project was to generate hydrodynamic model results to support the client’s 30% design phase for riverbank stabilization and physical stability analyses within the B1a project area. These modeled conditions and resulting outputs provide a comprehensive understanding of the forces exerted on the sediment bed, which are critical for the design and evaluation of proposed remediation and stabilization measures.

Application

EFDC+ and EFDC Explorer (EE) were utilized to develop all testing scenarios and to perform post-processing of the model results. Since the client requested higher spatial resolution within the B1a area, a nested model with refined grid cells in the Willamette River was developed. The nested model maintained consistent hydrodynamic settings with the latest validated large-scale model to ensure continuity and accuracy.

To simulate the different conditions:

• Flood simulations: The 1996 flood and 100-year return period flood were modeled by adjusting both upstream inflow and downstream stage boundary conditions to represent the respective hydrologic events.
• Wind-wave simulations: Based on client specifications, multiple scenarios were developed to represent various wind speeds and directions. Each simulation was run for one day to allow the model to reach a dynamic equilibrium state.

The final products included:

• Flood scenarios: Time series of depth-averaged velocity and bed shear stress, as well as spatial outputs of water surface elevation, water depth, and bed shear stress at the time of maximum shear. These results were delivered as individual GIS shapefiles.
• Wind-wave scenarios: Model outputs near the end of each wind stage, including total bed shear, current-induced shear, wave-induced shear, flow velocity, wave height, wave period, and water depth.