Managing floods in a changing climate for a green future

By Urban Development on Thu, 21 November 2013

Written by Amy Leung, Director of Urban Development and Water Division in Southeast Asia

Climate change, population growth, and urbanization are bringing some of the greatest challenges of our time. Just a few days ago we experienced one of the most powerful storms in history, Super Typhoon Haiyan, which devastated the Philippines, killing thousands. The same storm also affected northern parts of Viet Nam and the People’s Republic of China. Unfortunately rising temperatures and warming oceans mean the Asia-Pacific region is likely to experience even heavier rainfall and fiercer, more frequent storms in the future.

The prospect of a rise in extreme weather events, as well as flooding linked to urbanization and changing land use patterns highlight the urgent need for stepped up climate adaptation responses. Our “business as usual” development stance is no longer sustainable economically, environmentally, and socially. Nor is the mere adoption of new technologies. Instead holistic adaptation measures which provide multiple benefits to urban communities and ecosystems must become the new norm.

An example of this can be seen in the Netherlands. Here, the Dutch are developing multipurpose solutions―offering incentives for green roofs; designing public squares and garages that double as catch basins for rain and floodwater; and constructing floating houses and reservoirs that double as recreational areas. One of the innovative ways the Dutch have approached flood management is through Rotterdam’s water plazas. The plazas operate like any other public square during dry season, with steps that people can sit on, allowing space for special events. When it rains, water from surrounding streets is directed into the square through drains with filters, pooling clean water and relieving pressure on surrounding drainage. The square then drains at a much slower rate through a central point. The design of the plazas even allows rainfall to add to the square’s appeal as levels and channels open up little ponds, rivers, and water features. If a really big storm fills up the plazas entirely with water, the plaza would function solely as water basins.

In the United States too, action has been taken in response to extreme climate events. In some coastal wetlands, like Oakwood Beach, in Staten Island, New York, U.S.A., in the aftermath of Hurricane Sandy in 2012, the government gave residents the option to take part in a home buyout program, with those accepting the offer having their homes demolished, and the land no longer being made available for redevelopment.  Of the 185 residents in one small community in Oakwood Beach, 184 agreed to sell their homes to the State of New York at pre-disaster value, with additional incentives to make the move easier. Buyouts, which are voluntary, encourage people in areas vulnerable to recurrent floods to move. A buyout by an entire community requires unity and a collective desire to move.

Buyouts though are not always voluntary. In Overdiepse Polders, Waspik, Netherlands, the government made a hard but necessary decision to involuntarily relocate 17 farming families with their land turned into a river spillway site during occasional floods. This took pressure off a canal, reducing the water level by a foot, and sparing 140,000 residents of Den Bosch, upriver, during floods. In return the remaining residents of Overdiepse Polders asked the government to build mounds along the southern edge of the spillway, high enough to allow their land to remain dry. It wasn’t easy, but through the cooperation and participation of all stakeholders, they made it happen.

ADB’s Green Cities Initiative makes a compelling case for a holistic approach to adaptation across urban centers in Asia and the Pacific. The same message is also conveyed in an upcoming joint publication by ADB and the International Water Association entitled:  Unflooding Asia the Green Cities Way.

Many of the events which are currently taking place cannot be prevented, but with greater commitment and a shift in our current mindset, we CAN build more resilient and less vulnerable cities.