Few experiences deliver a sense of powerlessness quite like a flood. The devastating deluge that Hurricane Harvey brought to Houston and other parts of south Texas has left tens of thousands homeless and as many residences and buildings uninhabitable. Meanwhile, before Texans have even come to terms with the extent of the damage, Hurricane Irma has wrought havoc in the Caribbean and Florida, devastating entire communities and countries.
Although the vicissitudes of climate are partly to blame for any meteorological calamity, poor design plays a significant role. The Bloomberg BusinessWeek article “Harvey Wasn't Just Bad Weather. It Was Bad City Planning” outlines the oversights in urban design and planning policy that exacerbated that hurricane’s effects, including excessive paving, diminished areas of coastal prairie, and “one of the nation’s most relaxed approaches to building codes, inspections, and other protections.” Additionally, climate change—which scientists argue was responsible for the severity and duration of the storm—is itself a problem of our making.
Reports that flooding will continue to become more frequent and costly around the world should elicit concern in the design and planning community. Not only is the climate more volatile, but land shortages continue to encourage the construction of buildings in flood-prone areas. Houston’s Harris County alone permitted more than 8,600 structures to be built in 100-year floodplains—land where floods have a 1-percent probability of occurring in any year. Though architects may have little control over such development trends, innovative examples of resilient construction reveal strategies that designers can pursue to increase the protection of buildings against flooding.
Many developed sites, particularly in urban areas, are designed like bathtubs: vast systems of impervious surfaces hold stormwater and channel it toward drain inlets. This arrangement works until a significant rainfall event occurs and overwhelms the system. Green roofs offer a viable strategy to delay stormwater runoff and encourage its gradual absorption into the earth below the site. Increasingly, green walls are being employed for a similar purpose. For example, a living wall designed by the Green Infrastructure Consultancy covers 3,767 square feet of the façade of the Rubens hotel in London. Not only does the wall provide occupant advantages, such as improved insulation and air quality, but it also acts as a giant sponge that moderates the passage of stormwater from the building’s roof onto the paved streets below.
At ground level, many materials offer alternatives to continuous expanses of concrete and asphalt. Specially made porous concrete may be used where rigid surfaces are required, and systems like Ferrari BK’s Lunix interlocking blocks create a visually interesting mix of hard paving and natural ground cover. (For more information on pervious, porous, and permeable paving strategies, check out The Stormwater Report.)
Since the stormwater delay and groundwater recharge processes can still be overwhelmed by a significant rainfall, increasing the physical distance vertically between a building floor and the ground plane is an obvious solution. For his design of the Arnold house in Houston’s Braeswood neighborhood, local architect Brett Zamore, AIA, elevated the first floor 16 inches above FEMA requirements for a 100-year flood zone. When Harvey struck, the water rose to a level just two stair risers away from the finished floor—and above the datum FEMA stipulated. The case of the Arnold house is incentive enough for architects to take advantage of the extra height as a design feature. Nha4 Architects also prioritized height for a recent residential extension in Thái Hòa, Vietnam, which consists of a cantilevered volume over a stone plinth that is almost 5 feet above ground level. When the next deluge overwhelms the existing portion of the house, the occupants can shelter in the elevated addition.
As a last resort, architects can accept that their buildings will flood. Such a situation need not be catastrophic, however. Milan-based Act Romegialli architects retrofitted an existing ground-level apartment in Venice with flood-resistant materials. Due to the frequent acqua alta ("high tide") phenomenon of the structure's site, the firm reconfigured the first floor to act as a holistic waterproof container made of reinforced concrete. “The constant concrete wall perimeter level of [5 feet] gives the internal space a sense of protection and intimacy,” the firm writes on its website. “The tank containment rim thus becomes a step, a shelf, a furniture support, and floor for the kitchen and bathroom.”
Several firms have also explored the idea of structures that rise with the tide. One well-known example is the 2009 Float House, designed by Thom Mayne, FAIA, with students for the Make It Right Foundation reconstruction of the Lower Ninth Ward in New Orleans. A similar, more recent project is the Amphibious House designed by Baca Architects in London. Located on a flood-prone island in the Thames River, the residence consists of two structures: a self-contained, lightweight timber building that rests freely on—and within—a basement-story container composed of steel sheet piling. When the water level increases enough to submerge the site, the buoyant inner volume will rise accordingly, its waterproof concrete base keeping moisture out from below. The lower “wet dock” has a porous base, thus allowing water to recede into the ground. Like the Float House, the Amphibious House employs vertical guideposts that constrain the movement of the upper structure so that the building does not migrate from its site.
Ultimately, strategies that increase the resilience of individual structures in increasingly flood-prone environments should also contribute, albeit in a small way, to the larger problem. For example, living roofs and walls not only provide local advantages but also reduce urban heat island effects that exacerbate climate volatility. Likewise, the use of low-embodied energy materials, such as timber, can represent a reduction in manufacturing-related carbon dioxide emissions in comparison to conventional construction materials, namely steel and concrete.
Of course, flooding is a problem that requires macro-level, systems-based solutions involving many disciplines beyond architecture. However, by applying smart design approaches on a more consistent basis, architects can implement granular changes that add up to comprehensive benefits.
