Case study presentation at the 2024 Pacific Workshop on Nature-based Coastal Solutions

Associated Engineering is proud to be a supporting sponsor of the 2024 Pacific Workshop on Nature-based Coastal Solutions, hosted in Vancouver by the Pacific Chapter of the Nature-based Coastal Solutions Community of Practice from October 8th to 10th!

Water Resources Engineer, Eric Finney, will be presenting a case study titled "Colquitz Park: Applying Green Shores Principles in an Estuarine Environment in Southern Vancouver Island" during the third day of the conference (October 10th) in Session 7 beginning at 1:00pm.

Colquitz Park lies on the left bank of the Colquitz River which discharges into a shallow basin (Portage Inlet) in Saanich, BC.  The shoreline has experienced significant erosion and loss of riparian habitat due to encroachment of residential areas and regular mowing. The District of Saanich desired that the park be restored using nature-based solutions, whilst aiming for Green Shores for Shoreline Development (GSSD) accreditation. Objectives included to stabilize the shoreline, improve the riparian habitat, identify climate-related risks and solutions, and provide guidance to recreational activities.

Recognizing that riverine flows in the urbanized Colquitz River would play a significant role in erosion processes, our project team, led by Associated Engineering with support from DHI, focussed on modelling this channel. We conducted a frequency analysis on available flow data and adjusted these values for an assumed return period based on an analysis of projected climate change effects. We then developed a HEC-RAS 2D model of the channel and the basin considering various tidally-influenced boundary conditions that reflected different sea level rise scenarios.

The modelled results were used to develop several restoration concepts for review by the client. These concepts incorporated specific nature-based solutions intended to embody green shores principles, with the goal of gold level certification. Techniques implemented include strategic vegetation selection and placement, redesigning existing storm outfalls to include more natural features, main channel regrading, restraining public access to designated areas, and inclusion of limited erosion protection through adding channel roughness. The hydraulic model also represents a value-added feature of the project which can serve as a backbone for future flood mapping for the client.

Implementation of the design is planned for the summer of 2025, with final assessment of Green Shore certification occurring shortly thereafter.