Ducks Unlimited Canada (DUC) is leading the Sturgeon Bank Sediment Enhancement Pilot Project (SBSEPP), which involves testing and demonstrating how dredged sediment from the Fraser River estuary can be beneficially used to restore tidal marshes and simultaneously provide coastal flood protection to the low-lying City of Richmond in the Metro Vancouver region in British Columbia.
Since the 1980s, approximately 260 hectares of ecologically important, low-elevation bulrush tidal marshes have been lost throughout the Fraser Delta, including at least 160 hectares at Sturgeon Bank. Sturgeon Bank is a provincially-designated Wildlife Management Area within the unceded, traditional territories of the Coast Salish peoples, including the xʷməθkʷəy̓əm (Musqueam) and sc̓əwaθən məsteyəxʷ (Tsawwassen) First Nations, and west of the City of Richmond, British Columbia. Rising sea levels, and other stressors, threaten the survival of the remaining intertidal wetlands seaward of Richmond’s dyke system. Tidal marshes attenuate wave energy and promote sediment accretion on Sturgeon Bank, providing flood risk management benefits to the City of Richmond, which is vulnerable to the effects of sea-level rise. Without intervention, the anticipated continuing loss of marsh ecosystems, coupled with relative sea-level rise, will contribute to increased coastal flood risk.
The SBSEPP is designed to mimic natural riverine sediment delivery processes by using a temporary floating pipeline to pump dredged sediments onto the intertidal mudflats at Sturgeon Bank. This pilot project seeks to address marsh sediment budget deficits caused or exacerbated by dredging for navigation, and the construction of river training structures in the Fraser Estuary. These activities have deprived the marshes of foundational materials needed to enable marsh accretion to keep pace with sea-level rise, and delta subsidence. This pilot project provides a unique opportunity to test an ecosystem-focused, nature-based solution to coastal flood risk management, and to demonstrate a “proof-of-concept” for potential broad application across the urbanized Fraser River delta.
Of critical importance to determining the feasibility of the SBSEPP and possible future larger-scale beneficial use of dredged sediment, and to guiding future sediment placements, are (i) the potential for sediments placed on the intertidal mudflat to be transported into existing salt marshes by waves and tidal hydrodynamic processes, and (ii) the influence of placed sediment on wave- and high-water-level-driven hazards (e.g., dike overtopping) at Richmond.
MASc student Jeremy Karkanis is working with partners at DUC and the National Research Council of Canada to develop hydrodynamic and sediment transport models for Sturgeon Bank. The models will be used to simulate far-field sediment plume transport and dispersion by waves and tidal hydrodynamics (i.e., to identify sediment transport pathways, areas of deposition, and source-receptor relationships), and to evaluate the potential impacts of bed elevation changes resulting from deposited sediments on storm-driven (wave and water level) hazards at Richmond. A comprehensive field monitoring program will be used to support the modelling and to characterize complex mudflat system dynamics. The research outcomes will inform future phases of the SBSEPP, marsh vegetation dynamics simulations, and the feasibility of scaling up the beneficial use of dredged sediment for coastal flood risk management in the Fraser Estuary.