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    Design for Flooding


    The Opportunity

    Design and enhancement of the water balance and resources of watersheds, aquifers, floodplains, and built infrastructure can mitigate and help to prepare for severe weather and climate change.

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    Flooding can benefit a region if it is anticipated. Rain collection from both intermittent and storm flooding of natural areas serves to replenish and stabilize the vegetative soil layer, and cleanses areas susceptible to salinity. Plentiful rain moving across the land and stored in groundwater aquifers provides inland waterways for wildlife habitat and for countless human purposes, including food, fire safety, recreation, and freshwater essential to all of life.

    We present a new approach for designing buildings and communities, with five defining concepts.

    Design for Resilience

    Resilient design prepares for extreme storms and flooding of inland watersheds and coastal areas to provide resiliency and emergency preparedness for natural disaster. The concept of resiliency applies lessons from natural systems to design for extreme conditions using strategies of buffering, zone separation, redundancy, rapid feedback, and decentralization. Resilient design presents a new paradigm for design and building professionals to create buildings, communities, and regions that restore and improve our water resources and that mitigate threats of extreme weather and climate change.

    Protect and Extend Ecosystem Services

    The concept of ecosystem services recognizes and helps to credit the economic, health, and social benefits derived from functioning natural environments — land, vegetation, water, and living organisms. Natural landscapes provide clean air, freshwater storage, diversity of plants and wildlife, crop pollination, groundwater recharge, waste decomposition, and recycling of nutrients. Forests provide greenhouse gas mitigation and regenerative response to fire, drought, flooding, and climate change. Wetlands control erosion and flooding, remove pollutants from water, and recharge the groundwater reservoirs that we all rely on for our water supply. Coastal marshes, wetlands, and mangroves provide important buffers to coastal storms and storm surge.

    Create Watershed Plans and Sustainable Stormwater Systems

    Watershed planning is a multidisciplinary approach to water as a valued resource considered at each phase of its flow and use within natural systems defined by specific geological and climatic conditions. This concept focuses on water flows within the natural systems of regions, including restoration of the subsurface aquifers and integration of water and green infrastructure in urban development.

    Sustainable stormwater design is an approach that reduces disturbance, protects and restores natural features, and uses soil and vegetation to manage stormwater. The focus of this concept is on designs that improve the local and regional water balance as a resource and principal element of flood-control engineering.

    Implement Floodplain Management and Flood-Resistant Design

    Floodplain management is a correlate and extension of watershed planning adopted into practice, focusing on the impacts of flooding. It includes land use policies and regulations for development in flood-prone areas, restoration and protection of natural resources and functions of floodplains and contributing watersheds, and flood-resistant design. New "smart grid" techniques allow automatic monitoring and rapid response to river flooding as well as monitoring dikes and other flood-control measures.

    Flood-resistant design includes avoidance by relocating buildings and infrastructure out of harm's way, along with flood protection and mitigation measures: raising buildings above code-mandated flood levels, engineering buildings for severe wind and wave impacts, and using materials that are waterproof or otherwise impermeable to water damage.

    Practice the Precautionary Principle

    Designing to code minimum is not sufficient as a professional and due-diligent response to flooding and other increasingly severe impacts of extreme weather and climate change. The way we have built on the land — meeting only the minimum regulatory requirements under present law — has made things worse.

    Following current planning to code minimums in many cases aggravates flooding beyond the project boundaries by fragmenting natural areas, increasing hardscape that increases storm overflows, and eliminating open space and vegetation that historically have served as natural filters and buffers. At the same time, increasingly severe weather events are exceeding guidelines and regulatory minimums represented in codes, which are slow to respond to new information and need for higher standards.

    The design of buildings, especially in areas exposed to flooding, involves risk assessment by designers and building owners. Risk assessment requires decisions that must somehow mediate between options, some riskier than others, some costlier than others, some more difficult to implement. Design is a response to risk in the charge to provide shelter and habitable spaces and livable communities, fulfilling the broadly defined obligation to the public to protect life, safety, and welfare.

    The precautionary principle considers that if an action or policy might cause severe or irreversible harm to public health or the environment, restraint is called for, and, in the absence of verifiable documentation that harm will not result, either to not undertake the action or to require consideration of all feasible and less risky alternatives.

    The precautionary approach is defined in the 1992 Rio Earth Summit Declaration:

    In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

    The precautionary principle is a response to risk of possible or probable harm to health or environment, even if the extent of harm is not yet fully established or documented. It is an ethical principle. When adopted as a guideline for public policy and where there is credible evidence of potential harm if an action is taken, then immediate steps must be considered to mitigate, reduce, or eliminate that threat while also pursuing risk assessment studies.

    The precautionary principle is properly applied to actions that are potentially irreversible, such as planning where biodiversity and ecological services may be irretrievably lost or reduced. The principle suggests that "interventions must be reversible and flexible. Any mistakes must be correctible."*

    * Ticknor, Joel, Carolyn Raffensperger, and Nancy Myers. The Precautionary Principle in Action: A Handbook. Science and Environmental Health Network, 1997.   >>>

    Discuss this article in the Architecture Forum...

    Donald Watson, FAIA, an architect and planner, is former chair of the Yale School of Architecture's Environmental Design Program, and former professor and dean of the School of Architecture at Rensselaer Polytechnic Institute. He received the 2002 ACSA Distinguished Professor Award and the 2005 AARC Haecker Leadership Award for Architectural Research. His publications include Climatic Building Design, winner in the "architecture and urban planning" category of the American Publishers Award for Professional and Scholarly Excellence.

    Michele Adams, P.E., a water resources engineer, is principal and founder of Meliora Environmental Design in Kimberton, Pennsylvania. Her work encompasses environmentally sensitive site design and sustainable water resources engineering.

    This article is excerpted from Design for Flooding by Donald Watson and Michele Adams, copyright © 2011, with permission of the publisher, John Wiley & Sons.



    ArchWeek Image

    Weeks of extremely heavy rains in late December 2010 and early January 2011 led to massive flooding across eastern Australia in the states of Queensland, New South Wales, and Victoria. This NASA satellite photo from January 9 shows flooding of the Fitzroy River in Rockhampton, Queensland, a city of about 75,000 residents. Image does not appear in book.
    Photo: NASA Extra Large Image

    ArchWeek Image

    Flooded houses in St. Bernard Parish, Louisiana, about a week after Hurricane Katrina devastated parts of the U.S. Gulf Coast in 2005.
    Photo: Michael Rieger/ FEMA Extra Large Image

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    A debris staging area in the Lakeview area of New Orleans, July 2008. Some 58.8 million cubic yards (45 million cubic meters) of debris had been collected in Louisiana by that time, following Hurricanes Katrina and Rita.
    Photo: Andrea Booher/ FEMA Extra Large Image

    ArchWeek Image

    Impervious surfaces such as pavement, roofs, and landscaping can transform nearly all precipitation into runoff, as illustrated in this sample precipitation diagram for the Philadelphia, Pennsylvania, region.
    Image: John Wiley & Sons Extra Large Image

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    In contrast, a natural landscape in the Philadelphia region returns most precipitation to the atmosphere through evapotranspiration, resulting in comparatively little runoff.
    Image: Wiley Extra Large Image

    ArchWeek Image

    Diagram illustrating the global carbon cycle. Where known, the mass of each carbon sink and process is indicated in gigatons of carbon (Gt C).
    Image: Wiley Extra Large Image

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    Clouds form when warm thermal updrafts encounter cooler air at higher altitudes, causing moisture in the warm air to condense.
    Photo: © Reg Morrison Extra Large Image

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    Design for Flooding: Architecture, Landscape, and Urban Design for Resilience to Climate Change by Donald Watson and Michele Adams.
    Image: Wiley


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