Floods in urban areas are a growing risk in many countries of the developing world. This column explains how integrated actions to adapt to flooding are urgently needed in most cities in Africa, Asia and Latin America – particularly to help deprived people living in areas of inadequate housing. We must comprehend the links between geophysical processes, human drivers, and human victims at multiple scales. We must also respond at all levels – from individual households to national governments, as well as international river basin management.
Understanding adaptation to flooding involves examining how everyday urban activities exacerbate flood risks. It also requires understanding of how to reduce the inequitable exposure to flood risks at all levels– from the individual household to national governments, and international river basin management.
Global, rural and urban changes all affect one another. Coordinated adaptation must take account of the differing scales of flood problems arising from: highly localised thunderstorms, huge flood flows on major rivers produced by tropical cyclones, overflowing urban drains and channels, and shoreline inundation from large lakes or seas during unusual storm surges or seismic wave events.
The actual height and extent of any given flood is determined by the nature of the ground surface, the dimensions of the channels or coasts along which flood flows develop, and by local obstructions to water movement. Diverse human actions – collectively forming the ‘human dimensions’ of flooding – change the land cover, alter the ability of water to infiltrate, and impede the flow of water along channels.
People adapt to local floods at the household and community level by minimising losses and using property protection strategies such as building barriers to water, raising houses on stilts, and obtaining flood insurance. But such actions by individual households are seldom coordinated. Protection of one dwelling may lead to worse flooding of a neighbouring property.
Community level action is often difficult in deprived communities within informal settlements. Social resilience is often weak, and communities are unable to mobilise their own resources quickly and effectively. The social capacity to adapt to, and recover from, flooding is thus far lower than it could be.
Municipal adaptation plans often suggest removing people from informal settlements, which are regarded as illegal developments. Sometimes such municipal and national efforts to adapt by relocation are thwarted by powerful local politicians. Municipal flood adaptation, where it exists, is mainly concerned with structural works to contain and evacuate floodwater quickly.
In Kuala Lumpur, Malaysia, for example, concrete walls built 40 years ago direct flood waters through the city centre, often so quickly and at such a height that the water blocks flows from tributaries entering the river downstream, causing flooding of much low-lying housing. Such shifting of problems, rather than their reduction or alleviation, usually produces environmental injustice where deprived communities suffer and more affluent groups benefit.
Although adaptation to flooding needs to be planned at the river basin scale, river basin management usually aims to ensure reasonably equitable shares of water supplies for agriculture, urban use, hydroelectricity, and downstream fisheries. Dealing with flooding is often a secondary concern.
In Africa, the prime concern of Egypt and the Sudan is to have enough water from the River Nile to supply their cities and grow the food that people need. Upstream states need the hydropower from dams, and water for their growing populations. Yet farming and forestry have caused erosion that reduces the capacity of reservoirs to hold water, sometimes requiring flows from the mountains to be released early and causing flooding of downstream farmland. Such events illustrate the need for flexible water allocation, biodiversity, water quality protection, flood control and infrastructure maintenance.
If we are to adapt to flooding, we have to recognise the responsibility of those who change things upstream to ensure that their actions do not make things worse for people on or near the floodplain downstream. Those who make flooding worse by changing the landscape do not usually suffer the consequences of their actions. We must comprehend the links between geophysical processes, human drivers, and human victims at multiple scales.
Government agencies are slowly recognising the importance of community organisations and networks in flood adaptation. Such collaborative actions should not become an excuse to off-load public responsibilities.
National and municipal governments should work together to deliver flood mitigation and adaptation through local, regional or national action at appropriate scales. Communities will deal with problems entirely within their areas, local governments will act on issues arising within their boundaries, while national governments or international river basin organisations will deal with problems across many administrations.
Examples of good practice abound in terms of local action and individual flood adaptation procedures. Some municipal plans have multifunctional goals, but others may have a dominant single purpose.
Wider-scale collaboration is bedevilled by issues of how to achieve trust and cooperation between different sectors of urban society, and how to overcome decades of social division and inequality. Mistrust, such as the suspicion of local government by national governments and the suspicion of NGOs by most governments in the Global South, makes effective working at different scales within any city difficult.
A key issue is getting people who are highly concerned about the immediate livelihood and safety issues around their own homes and businesses to see the bigger picture and to fit their flood adaptation into the wider context. The recognition that the victims of flooding are usually not the perpetrators of the aggravating actions is important for all sectors of society.