Restoring the critically endangered Hillman Marsh ecosystem using nature-based solutions

Reinstating nearly 250 hectares of wetland providing ecological, habitat, carbon sequestration and water quality services

Covering approximately 400 hectares, Hillman Marsh is a designated Provincially Significant Wetland. Historically, the marsh was a thriving ecological system providing critical habitat to aquatic endangered species and numerous migratory bird populations, while providing ecosystem services such as water quality benefits. However, cumulative stresses from human development and climate change, particularly rising lake levels, have severely threatened its ecological value. To restore this vital ecosystem, the Essex Region Conservation Authority is leading a collaborative effort with DHI and SJL Engineering Inc. Using MIKE Powered by DHI technology, the team is developing nature-based solutions that will strengthen habitat resilience and ecological health. This initiative is supported by grant funding from Environment and Climate Change Canada (ECCC) under the Great Lakes Freshwater Ecosystem Initiative (GLFEI).

Challenge

In addition to the significant loss of habitat and ecosystem services once offered by the Hillman Marsh, the propagation of lake waves through the newly breached barrier system and into the marsh presents a significant risk to the residents and agricultural lands within the interior of the Pelee Peninsula on Lake Erie, in Ontario Canada. The marsh is surrounded by a perimeter of dykes, which were constructed from native local materials including clay and peat. The interior lands are low-lying, with much of the Pelee Peninsula featuring elevations well below the 100-year flood level. There is potential for widespread flooding of more than 2,000 hectares and direct economic damages of up to $50 million should the dyke suffer a breach based on the historical 100-year flood level. 

Solution

The overall objective of the Hillman Marsh and Barrier Beach Restoration Project is to create a restored marsh environment with protection from lake waves and storm surge achieved through the design and implementation of a nature-based, dynamically stable, engineered artificial barrier feature. To achieve this, the barrier is to be designed in a hybrid manner, combining several approaches to reduce wetland exposure, increase resilience and provide shoreline stability including traditional engineering techniques (e.g. breakwaters, headlands, reinforced dykes) with nature-based or green infrastructure (e.g. artificial reefs, sediment bypassing, beach nourishment, boulder clusters, dune restoration, barrier re-vegetation, etc.).

DHI commenced this multi-year project in 2024 with a comprehensive field campaign, deploying wave monitoring, streamflow and water level instrumentation within the marsh. The team is using MIKE 21 Spectral Waves, Hydrodynamics, MIKE 3 Mud Transport and MIKE 3 Wave FM models to assess the marsh baseline and develop nature-based hybrid design solutions to protect and restore the marsh habitat. 

The numerical models integrate vegetation dynamics and morphological processes to understand the system’s response to future climate stressors and the proposed solutions. The final concept is being tested and refined in the physical model basin at the Federal Ocean, Coastal and River Engineering Research Centre in Ottawa. Once the design is finalised, plans will be prepared for implementation, construction, monitoring and long-term adaptive management of the project.