Recently, on a particularly murky day while driving into Toronto, I noticed the agitated waters of Lake Ontario, and the trough and crest cycle that easily cleared the concrete wave breakers. Though the lake was choppy, knowing that it is historically well behaved took some of the edge off my worries about living so close to a major body of water. However, Toronto is not immune to extreme weather disasters. We only have to remember the sudden storm of July 2012, which submerged the downtown core and commuter arteries, including railway lines, subways and expressways, under 90 millimetres of rainfall. The resulting two-hour flash flood cost the city $60 million.
It was also a reminder that the recently completed Corktown Common – a 7.3-hectare park at the water’s edge, designed by Michael Van Valkenburgh Associates of New York – is an essential precaution for rising waters still to come. The park, built on a flood plain, rises up 8.5 metres from ground level and is situated on the top of a berm that is intended to block the Don River from engulfing the surrounding 200 hectares, a swath of land that contains the financial district. Even a relatively well protected metropolis like Toronto can’t afford to take flooding lightly.
Addressing the tension between building and ecology is not a new challenge, though. German geographer Carl Troll first outlined the concept of landscape ecology in 1938, while landscape ecologists Richard T. T. Forman and Wolfgang Haber both advised on the necessity of bridging the gap between natural and human ecosystems. Before this, the Amsterdamse Bos park, built between 1934 and 1970 by Cornelis Van Eesteren and Jacopa Mulder, served as a benchmark. Defiantly at odds with the purely decorative 19th-century design, the 1,000-hectare locale was conceived as a “production site” where natural and artificial processes intertwine. It provides a vast recreational space, while functional processes support its precarious placement four metres below sea level. Amsterdamse Bos is one of the first municipal green spaces to employ native plants as a land reclamation strategy; and its bodies of water, including ponds, lakes and ditches double as flood drainage systems.
Even with this impressive project in our midst, landscape architecture has been considered mostly decorative. Recent super-storms – including the flood that devastated Alberta last June, temporarily displacing 100,000 residents – have made it clear that nature has outwitted our preventive strategies of just blocking it out. Inadequate infrastructure has become a global problem. Several coastal cities in India and China face the highest risk in the world, according to the Organisation for Economic Co-operation and Development, which projected climate change 50 years into the future. Guangzhou and Shanghai both appear on the top 10 list of most vulnerable cities by population density (as a comparison, New Orleans did not make the list). As for cities with the most to lose in infrastructure, Miami takes the lead with an estimated US$416 billion, followed by Guangzhou, New York-Newark and Calcutta.
Governments and local officials increasingly recognize the cost of ignoring weather patterns, and they are seeking innovative options, albeit slowly. The approach that is gaining the most momentum engages the environment in a much gentler way, by evaluating the figure-ground relationship that works with, not against, severe weather. Rather than try to block out downpours, hailstorms and torrential winds, the aim is to absorb them into the urban fabric.
At an international round table held in Toronto recently, Kongjian Yu, a professor at Peking University and founder of the landscape architecture firm Turenscape, spoke about water
security and sustainability. He advocated incorporating nature back into our development schemes to abate the tides. This “green sponge” approach was used in one of his own designs for the Qunli National Urban Wetland, in the northeastern Chinese province of Heilongjian. Completed in 2011, the 34-hectare park soaks up the region’s heavy annual rainfall and frequent floods through a network of ponds and mounds containing native plants that delineate an untouched wetland. With the introduction of a landscaped buffer zone, a once dry and undesirable wetland has been reshaped to allow for self-managing storm water filtration and cleansing, and to encourage biodiversity. With its skywalk pathways, it also gives residents an idyllic environmental amenity.
Most landscape architects point to Hurricane Katrina as a defining moment when coastal cities collectively wondered what would come next. New Orleans has undergone a difficult recovery in the nine years since Katrina virtually washed away an entire residential ward. Local architect David Waggonner, principal of Waggonner & Ball, has taken up the cause of rethinking his city’s water management and inadequate levees. To catalyze real change, he believes there are two fundamental ways to approach the problem, one functional or operational and the other imaginative or mystical. For him, water has the capability to resonate with people on both levels. “Water management and design ask for both aptitude and attitudes,” he says. “Things that work can be beautiful as well as beneficial.”
After Katrina, he and a group of delegates, among them experts from universities and water management agencies in the Netherlands, developed a series of workshops and a plan to adopt Dutch principles of reintroducing water into specific urban areas. Termed the Dutch Dialogues, the initiative proposes retaining some of the water now routinely pumped out of New Orleans and building waterways, such as canals and retention ponds to accept it.
This would produce numerous benefits, among them preventing the city from sinking further, as pumping dries out the land and erodes streets and foundations. Water features like canals would also attract economic development. The Urban Water Plan, led by Waggonner & Ball, was introduced last September, and it incorporates such small-scale retrofits as integrated wetlands to store and filter storm water, and networks that monitor surface and groundwater for quality and water levels in real time.
Several of these projects are moving forward. The Mirabeau Water Garden, for instance, consists of 10 hectares of parkland that incorporate flood risk abatement and natural filtration systems. Water from the Mirabeau Avenue trunk line is collected and filtered through a series of wetland terraces, ending up in a freshwater swimming pool.
While Katrina remains one of the worst hurricanes in U.S. history, Hurricane Sandy, which released its fury along the eastern seaboard in October 2012, delivered an effective wake-up call, especially in New York. Projects that began before the storm now carry a far more tangible sense of importance, especially in quelling public fears of another disaster.
Built on post-industrial land, the just-completed Hunter’s Point South Waterfront Park in Queens, New York, addresses the tensions between flooding and urbanity. Uniting the often disparate elements of landscape, infrastructure and architecture, the development, designed by Weiss/Manfredi and Thomas Balsley Associates, comprises ecological corridors, a soft shoreline designed to absorb flood waters, bioswale filters for storm water and a hurricane-resistant pavilion. Weiss/Manfredi describes Hunter’s Point as a first line of defence for the surrounding community, which became inundated by 1.2 metres of water during Sandy.
Balmori Associates’ project for the New York Police Academy in Queens, now nearing completion, organizes a system of three landscapes to ameliorate the flood damage. For example, a linear canal that bisects the campus is transformed into a gabion-walled terrace that works as a natural drainage ditch, redirecting the flow of up to 49 million litres of water. It also provides for appropriate, ecologic landscaped elements to sustain filtration and aeration and scrub water through displacement. Perimeter landscaping employs native vegetation and some 400 tree plantings, including lindens, tulip poplars, honey locusts and sweet gums.
British architect Geoffrey Jellicoe once postulated that landscape would one day dominate architecture as the reorganization tool of the built environment, as well as the human spirit. His prophetic logic, and the reality of our changing environment, is timely. A complex choreography of disciplines is proving to be the most effective way of addressing the inevitable ebb and flow of urbanity, a step in the right direction as we face up to new levels of extreme weather. As David Waggonner likes to say, “A disaster is a terrible thing to waste.”
Six landscapes with built-in resilience
OMA, Balmori Associates and water management engineers Royal HaskoningDHV teamed up to ameliorate the threat of flooding in the city of Hoboken, which is particularly vulnerable to storm surges and flash floods. The competition entry outlines four main tenets for preserving the water’s edge: resist, delay, store and discharge. The plan calls for commercial buildings and infrastructure, including levees, to defend against rising waters. Greenways around the city’s perimeter would contain holding tanks, and pumps would drain the excess water back into the Hudson River.
The Dutch have put landscape ahead of urban development ever since they implemented dikes centuries ago, as a means of controlling the seasonal floods that affect the Netherlands, up to 30 per cent of which sits below sea level. Climate change has spurred new areas of exploration, such as self-sufficient floating cities that can withstand storm surges and rising tides.
In 2010, Dutch firms DeltaSync and PublicDomain Architecten completed a 1,500‑square-metre pavilion moored in Rotterdam’s Rijnhaven Harbour. Its steel and ETFE domes feature a demand-driven climate system, with solar heating and on-site waste water treatment and recycling.
Managing director Rutger De Graaf says municipal officials support the initiative, going so far as to create a designated zone for an assemblage of floating islands as part of the harbour’s redevelopment.
The Chinese landscape architecture firm Turenscape turned an undesirable and inaccessible wetland into an environmental amenity for Qunli New Town, a city development in the north. The park takes full advantage of the region’s seasonal flooding and waterlogged soil by surrounding the periphery of a 34-hectare wetland with a necklace of ponds and mounds. The built landscape functions as a natural storm water filtration system and a cleansing buffer zone for the wetlands at the park’s core. Nature is left untouched, with a network of paths and skywalks allowing visitors to wander above and among the treetops without affecting the self-sustaining ecosystem below.
The newest park along the East River in New York has already had its endurance tested by super-storm Sandy. The construction site became submerged under more than a metre of water, yet it remained unscathed. Officially opened in August 2013, the two-hectare park serves as the focal point of a much larger development that will contain 5,000 affordable housing units and additional green spaces. Collaborators Thomas Balsley Associates and Weiss/Manfredi equipped the project with various water management features, including bioswales that filter storm water, and salt-tolerant native plantings that act as natural sponges. The curved pavilion’s white canopy is made of pleated steel, which helps collect and re-direct runoff.
One of Toronto’s most vulnerable flood zones lies at the mouth of the Don River, which runs through the city and feeds into Lake Ontario. A major storm could swamp 200 hec-tares of the surrounding land, including the financial district. Last year, a pavilion designed by Michael Van Valkenburgh Associates was constructed atop a man-made hill. The raised landscape will act as a berm, rerouting torrential waters away from high-density areas. It also gives visitors a lookout point that takes in the city skyline and the harbour.
As part of a larger redevelopment strategy for Calgary’s Rivers District, collaborators W Architecture of New York and Civitas of Denver have re-invigorated a 12.5-hectare island in the Bow River by restoring some of the parkland’s natural features, including two channels, one rocky, the other a wetland. While these are not designed to prevent flooding, they will help control storm water by allowing the river to flow where it wants, thereby preventing erosion. Last July, when Alberta was hit by its worst flood on record, the park became submerged under a metre of water. According to W principal Barbara Wilks, the local eco-system and amenities experienced minimal damage. The park officially opens later this year.