Tackling Urban Flooding
By Pamela Cox (*)
Flood risks are likely to complicate East Asia’s quest for steady growth, unless integrated flood risk management is built into regular urban planning and governance
|Flooding in HCMC, the dark side of rapid urbanization. Photo: Le Minh Khue|
East Asia’s cities are growing – fast. China announced last month that its population is now more than half urban, and other countries are following a similar path. Urbanization has no doubt supported the region’s dynamic economic growth, contributing to an overall reduction in poverty.
But there is another side to this tale that requires urgent attention. With growth, urban flooding has become an increasingly serious development challenge. We need only flash back to last year — the earthquake induced tsunami in Japan, large scale flooding in Thailand, and the tropical storm in the Philippines — to remind us of the devastation, economic damages and loss of human life that floods can cause.
Floods are the most frequent among all natural disasters, and the East Asia and Pacific region, along with South Asia, is particularly vulnerable. In the past 30 years, the number of floods in Asia amounted to about 40% of the total worldwide. More than 90% of the global population exposed to floods live in Asia.
As developing countries transition to largely urban societies, the concentration of people and assets has made urban flooding even more costly and difficult to manage.
Although floods affect developed and developing countries alike, the poor in urban centers are hit hardest, especially women and children. In developing countries, rapid expansion often creates poorer neighborhoods which lack adequate housing, infrastructure and services.
There are long-term consequences as well which erode development goals long after the waters have receded, such as diminished education opportunities, diseases and reduced nutrition. Research shows that severe floods can affect nutrition to the point where children never catch up and are permanently disadvantaged. Floods typically worsen poverty.
These risks can complicate East Asia’s quest for steady growth, unless integrated flood risk management is built into regular urban planning and governance. Such investments not only save lives, but also make economic sense. For example, a study by the World Bank in Europe and Central Asia shows that a dollar invested in hydro-meteorological services, including early warning systems, can yield up to six dollars in avoided damages and losses.
For policymakers, part of the difficulty of flood risk management is the complexity and scope of issues involved. Measures need to be judged not only in economic terms, but also take into account the vulnerability of people, equity, environmental degradation, biodiversity and sources of funding, among others. Success also depends on engaging people at risk at all stages, and coordination at the national, regional, municipal and community levels.
To help cities counter this complex challenge, the World Bank has released a practical guidebook “Cities and Flooding: A Guide to Integrated Urban Flood Risk Management for the 21st Century” which brings together experience and knowledge from across the world. The most effective way to manage flood risk is to take an integrated approach, combining both structural and non-structural measures — from hard-engineered construction of drainage channels to more natural alternatives such as wetlands and natural buffers, as well as early warning systems and awareness campaigns. The key is getting the balance right. Structures can be overcome by natural disasters beyond their design capacity. Current risks may change in the future as the effects of urbanization and climate change accelerate, requiring flexible solutions.
Many of these ideas are already at work. In Jakarta, a city which suffers from recurrent flooding, the World Bank is helping the local government rehabilitate parts of the city’s waterways. The project also looks at coordination between national and local agencies, introducing a new funding arrangement to enable the Indonesian Government to finance projects led by provincial governments.
Innovative ideas can bring multiple benefits over and above flood management objectives. In Kuala Lumpur, a tunnel almost 10 kilometers long and 12 meters in diameter carries traffic except during severe storms when it carries water. One tunnel provides flood control and traffic improvements at a cost that is far less than two separate measures.
Fortunately, the information age has equipped us with tools to better understand the type, source and probability of flooding and its impacts. Web-based flood forecasting systems are an increasingly accurate and effective way to share hydrological and hydro-meteorological data to a range of users.
Rapid urbanization means we have the opportunity to do things right the first time, so that urban centers can be developed sustainably. By working together to improve urban flood risk management, we can help make the tale of East Asia’s cities brighter.
(*)World Bank East Asia and Pacific regional vice president