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Landscape designs for extreme environments can be a walk in the park, says Mary Bowman of Gustafson Porter.

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Words by Mary Bowman

One of the interesting aspects of designing landscapes in different parts of the world is the various climatic conditions that inform the design of a project and the opportunities it presents.

With projects ranging from tropical rainforests to deserts, we are experienced in considering a wide range of external conditions. Our designs respond to changes in temperature, the amount of rainfall, sunlight and wind -- affecting not only human comfort but also the physical needs of plants and trees.

Gustafson Porter is currently working on projects in Singapore with fairly uniform climate conditions, a typical tropical rainforest climate, hot and humid. Day-time temperatures are fairly constant, settled around 30-34C, with night-time temperatures rarely falling below 23C. In combination with very high levels of humidity, external comfort levels can be quite challenging.

In Qatar, temperatures can climb to more than 40C during the summer months and can fall to lows of 14C in winter evenings.

Compared to 2,500mm of average rainfall a year in Singapore, annual rainfall in Qatar is only roughly 75mm. These extremes of rainfall and temperature will determine the planting schemes of our designs, how we need to drain surfaces and how we create comfortable and inviting spaces in external environments for people to enjoy.

One of the biggest challenges of designing in these hot climates is the provision of shade for people using outdoor space -- either through canopy structures or tree and shrub planting. As a general rule of thumb, people can comfortably walk a maximum of around 250m in the heat of the sun before they need to find respite in a shaded environment.

In both Singapore and Doha we have developed shade structures from materials that do not conduct or radiate heat. We have been working with materials such as ceramic extrusions and high-performance Ductal concrete, which create shade without radiating heat -- unlike steel or glass.

With air movement being encouraged, perceived temperatures can be lowered. For most people, more than 30C feels uncomfortable -- but if temperatures can be reduced to around 27-28C through shading, and breezes encouraged either through natural or artificial means, the external environment becomes much more pleasant.

For the Bay East Gardens in Singapore, the design concept is based on the creation of deep 'inlets' within the 2km-long site, which allows water and air to penetrate the interior of the park. The landscape design draws breezes from Marina Bay into the site.

Through water features located within the inlets, we are able to further cool these spaces, facilitating key gathering points for activities such as outdoor cafes and restaurants.

For our Doha project we have designed large, precast-concrete canopies to create shade for walks along the promenade and spaces for small kiosks and outdoor seating along the seafront. External spaces, particularly in desert climates, tend to be used more heavily in the evenings when the temperatures are cooler and nightlife can thrive. By breaking down the seawall edge and creating steps and terraces along the promenade, people can meet, sit, relax and appreciate the seafront views while enjoying the cooling breezes off of the water.

Shade can also be created through the use of extensive tree planting. Shrubs, trees and grasses help to mitigate heat transmission in hot, dry climates and have an evaporative cooling effect. The planting palettes are a mixture of native trees and plants with nonnative species that will work well in the environment.

Native desert-planting palettes can be quite limited so we have worked with the Royal Botanic Garden at Kew and its desert specialists to develop a plant list with a richer mix, offering a variety of colours, strong leaf shapes and grasses to add texture and movement. Due to their high irrigation needs, we rarely plant lawns in desert climates, only in limited areas as an amenity space for picnics and to accommodate young children.

For obvious reasons, the most important consideration for work in desert areas such as Doha is usually water. Typically, the irrigation supply will use TSE -- Treated Sewage Effluent.

Waste water from the surrounding development is treated to a high standard suitable for the irrigation of plants. However, this can turn into a chicken-and-egg situation; to generate enough waste water for irrigation, the surrounding development needs to be established and inhabited for a while. In developing countries of the Middle East, the irrigation water might often have to come initially from the potable water network until a good TSE supply is in place. For our projects, we specify plants and trees with low water usage. That said, most planting will require more water in the early establishment phases to support healthy growth.

In the Bay East Gardens Singapore, where shading and water inlets provide relief from the heat

In the tropics, the issue with water is the opposite: there is too much of it rather than too little. In Singapore, the challenge is to collect and store rainwater to be converted into drinking and irrigation water. For the Bay East Gardens, water drawn from the adjacent Marina Bay is used within the park. The freshwater bay was created some 10 years ago, when the new barrage at the outlet to the sea created a dam for the Kallang and Singapore rivers. Over the course of time, the salty sea water was converted into a fresh-water reservoir. Water for use in the park is taken from the bay and filtered through a natural pond, reed bed and gravel filtration system, and then used to irrigate the 2km-long park.

The most interesting differences between designing for tropical and wet climate conditions and very arid ones are that, in addition to the water requirements, the plant choice also differs hugely. In Singapore, we have used a wide range of tropical and sub-tropical plants including epiphytes, plants that grow on trees or rocks without the need for soil.

We recently worked on a design competition for the National Orchid Garden in Singapore. It was fascinating to explore the different conditions for growing orchids and how best to display them in a garden that gives visitors the opportunity to imagine and appreciate how they might be found in nature.

Many orchids grow on branches or tree trunks, quite high up from the ground. With Wilkinson Eyre Architects, which designed the highly successful glass houses for Marina South with Atelier One, we proposed a series of high level walkways that would allow people to see and experience orchids as they would be seen in nature.

The Bay East Gardens, Singapore, for which water is taken from the adjacent manmade freshwater Marina Bay

Of all the landscape work I have encountered in extreme climates, the most innovative is Gardens by the Bay, which I always visit when I am in Singapore. It is designed by Andrew Grant Associates with Wilkinson Eyre Architects, Atelier One and Atelier Ten.

It's a very different landscape aesthetic to our own, but very impressive and lovely to see growing and changing over the years. I was in Los Angeles recently and visited the terrace garden at Gehry's Disney Concert Hall by Melinda Taylor: the planting is reflected in the metal panels of the titanium facade of the building, and the soft curves of the pathways work well in contrast to the building's forms.

Cities like LA might initially not appear to have a climate as extreme as the desert landscapes in the Middle East, but the lack of water and the on-going droughts mean that landscape architects will generally need to take this into account to create designs for desert-like conditions rather than tropical gardens and highly irrigated landscapes.