How to handle flood risk is probably a question as old as human settlements (1). Still today, most urbanization takes place along river beds or coasts and on floodplains, on historically favourable agricultural areas with navigable waterways. Being flat, these areas are typically prone to flooding. With continued urban expansion and population growth, urban flooding is destined to increase. Indeed, as concludes by a recent World Bank Policy Research Working Paper, flood impacts have grown in the recent past and are likely to grow in to the foreseeable future (2).
Increased urban flooding, however, is not only due to there being more people, activities and infrastructure in the way of excess water. Land use changes in catchment areas, where for example fewer trees make rainfall hit the ground and the clearing of ground vegetation hamper infiltration, may cause erosion and concentrate run-off from rains into flash floods. On top of this, climate change may already be inducing increased concentration of rainfall itself into heavier downpours in many areas.
Moreover, land use changes forming part of the urbanisation process itself often exacerbate the risk for flooding. Through paving and construction, increased permeability of the ground disrupts natural drainable systems, as do encroachment into water detention areas such as ponds or wetlands within or around the urban areas. Many cities are also outgrowing their originally constructed drainage systems, which may also suffer from poor maintenance as well as clogging by household and construction wastes.
The impacts of urban floods, however, are not shared equally. Low-income citizens living in informal settlements tend to be the hardest hit. The commonly poor standard of houses is directly linked to the insufficient incomes of its owners or occupants. The lack of infrastructure, such as drainage, roads or water & sanitation infrastructure is produced by combinations of issues like the lack of political influence by dwellers, unclear legal status of settlements, as well as by the sheer fact that the area is prone to flooding.
That flood-prone areas have poorly developed infrastructure is usually justified by that the area is not suitable for residential use. And since they are flood-prone, such settlements cannot be legalised, which is yet another inconvenience for services such as water or solid waste collection. The alternative – relocation – has unfortunately a very poor track record. As commented by Alfredo Stein (Lecturer in Urban Planning at University of Manchester – Global Urban Research Centre) in relation to possible relocation of people away from the capital in Haiti: “You are only going to be constructing ghettos that are far away from where people will need to restore their economic lives” (3).
As an alternative to relocation plans, there are development plans. Whereas there may be cases where there is a lack of awareness about flooding risks, settling on flood-prone areas is generally driven by other priorities that take precedence over flood risks. (Proximity to labour markets is often a top priority, particularly where public transport is insufficiently developed.) Partly, in the aftermath of an event, there needs to be a coordinated partnership between humanitarian and development actors in order to reconcile demands of quickly restoring basic infrastructure and services, and the more time consuming aspiration of ‘building back better’ (4).
Looking forward, extending services and infrastructure investments also to flood-prone urban areas should be seen as a ‘no-regret policy.’ Higher-quality infrastructure is more likely to withstand flood events. This is sorely needed in precisely the generally affected areas. Further, housing structures may be planned to be more resilient. There are many community-level construction strategies including elevated housing (e.g. on stilts) or the more costly concrete bottom floor, potentially augmented with a second floor of less sturdy materials. Even very simple measures such as shelves can help reduce inconveniences and loss of property during flooding events. All such investments are helped by affording legality or at least the sense of permanence, also greatly helped by the provision of services and infrastructure.
In last year’s World Disasters Report 2010, the United Nations International Strategy for Disaster Reduction (UNISDR) proposed “Ten essentials for making cities resilient:” a) organisation and coordination to understand and reduce disaster risk, in collaboration with citizen groups; b) assign a budget and provide incentives to invest in disaster risk reduction; c) prepare risk assessments, which are to be readily available and discussed with the public; d) invest in critical infrastructure; e) assess safety of schools and health facilities; f) apply and enforce realistic building regulations; g) ensure education and training; h) protect ecosystems and natural buffers; i) install early warning systems and emergency management capacities, and last but not least; and j) ensure that the needs of survivors are placed at the centre of reconstruction.
I want to emphasise the last two; the focus on the people that are actually affected, and the issue of information. After all, floods are often cyclical or seasonal and generally predictable. Knowing what to do – in preparation as well as in emergency situations – can greatly reduce the problem presented by urban flooding. Fortunately, the basics seem to move in the right direction, as even though the number of flooding events and their economic impacts are steadily increasing; the immediate loss of life in relation to these events is not. This is attributed to more successful warning, evacuation and other emergency action, as well as investments in flood defences (5).
(1) Associated Programame on Flood Management (2008) Urban Flood Risk Management. A Tool for Integrated Flood Management. Flood Management Tools Series. World Meteorological Organization and Global Water Partnership.
(2) Jha, A., Lamond, J., Bloch, R., Bhattacharya, N., Lopez, A., Papachristodoulou, N., Bird, A., Proverbs, D., Davies, J. and Barker, R. (2011)Five foot high and rising. Cities and Flooding in the 21st Century. The World Bank.
(3) Cited in International Federation of Red Cross and Red Crescent Societies (2010) World Disasters Report: Focus on Urban Risk, Geneva, International Federation of Red Cross and Red Crescent Societies. Page 54.
(4) United Nations Human Settlements Programme (2007) Enhancing Urban Safety and Security. Global Report on Human Settlements 2007. Earthscan, London.
(5) Jha, A. et al (2011), page 14