operative ground of delta parks Great Lakes Basin shorelines
Andrey Chernykh and Leonard Flot
Splosh! The clam-like mechanical arm plunges into the water, drawing people closer to the edge. Children climb on the railing, oblivious to their parents’ warnings, to stretch out towards the open channel and see what will emerge from the deep. A little boy excitedly waves his toy truck at the towering machine before him. The clam resurfaces, dripping with water and muck, swivels toward a shallow pool, and releases a ton of mud that sends ripples racing. Workers keep careful watch as the crane operator signals to wrap up the digging. With a loud click, the pool begins to drain, followed by a fountain erupting into a nearby creek, earning a chorus of Wow! from the crowd. The water recedes, the lake bed emerges in blue-grey, yellow-grey and charcoal patches – a Jackson Pollock painting, a mesmerising mosaic of pebbles, sand, clay, silt and strands of seaweed. Beyond it, neat rows of soil stretch toward the lake, while trucks and machinery beep, grind and puff in a steady rhythm. A ferry horn breaks the atmosphere, sending people jogging along the tree-lined promenade past the cyclists, dog walkers, families, and benches filled with visitors enjoying the sun and hotdogs from a nearby stand. At the planter’s edge, someone’s soccer ball lands in wildflowers, stirring the insects only briefly, and then stillness returns. Conversations blend with the buzz of cicadas as workers finish their shift and lock away their equipment. The sun sets below the horizon as groups of onlookers enjoy a picnic and small BBQ in the open meadows until darkness falls, while the city continues to softly hum into the night. the challenge Standing on the beach of a busy urban park you listen to the water splashing on your feet. Looking out, the shore disappears and the surface of the water extends to the horizon and touches the sky, forming a razor-thin line barely visible in the haze of a hot summer day. Beneath this surface lie carefully managed underwater contours that shape the harbour and its bays. Periodically, a dredging vessel arrives to scrape the bottom, removing sand, silt, and debris that accumulate through natural deposition and storm events. This ancient practice, known as dredging, maintains the navigable depths of ports, harbours, and waterways. The challenge lies in what happens next. In the Great Lakes, dredged sediment is assessed under Canada and US guidelines to determine whether it can be returned to the water. 1 Traditionally, material is disposed in deep lake waters, or spread on land as fill, effectively returning it to its original state. However, when contamination exceeds disposal standards sediments must be stored within Confined Disposal Facilities, or CDFs 2 at significant cost.
Looking towards downtown Toronto along the shore of Lake Ontario: tiered wetlands in the foreground and an operating dredger in the background. Andrey Chernykh and Léonard Flot
As cities have grown, sediment composition has changed dramatically. Often contaminated and far from benign, dredged material has become a disposal problem rather than a resource. In the Great Lakes region, dredging commonly produces contaminated slurry destined for CDFs despite Province of Ontario policies that encourage beneficial reuse after remediation. 3 Meanwhile, waterfront development continues to favour spectacle-driven landscapes centered on leisure. This trajectory of development overlooks an opportunity to rethink shoreline parks through the fluvial processes that sustain them. Dredging projects around the world demonstrate how sediment management can work with deltaic flows and support their ecological systems, yet the current treatment of eroded sediment remains short-sighted in the face of growing environmental pressures. In light of all this, could the dredging activity and its by-product play a larger role in the realisation of a park as both an outdoor respite and as an ecologically and economically productive landscape?
1, 2, 3 Toronto and Region Conservation Authority (TRCA). Toronto & Region Remedial Action Plan, Restrictions on Dredging Activities . 2014.
38 on site review 49 :: shorelines
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