Disasters in their aftermath bring forth rising criticism leveled at those responsible for not only managing risks and disaster prevention, but also to the establishment accountable for urban planning. When disasters are deadly, with significant number of deaths involved, and stark pictures of horror, suffering, and loss widely exposed by the media – then, the criticism will increase to a crescendo of “poor management and negligence”. The deadly flash floods rang the alarms for town planners to heed and pay more attention to environmental standards in rapid urbanization and industrialization. The full breadth of environmental realities and the state of natural resources together with steps which guarantees human safety should have provided the over-arching framework in making t decisions pertaining to transportation, industry and urban construction. (i)
Handling the challenges of flood risks in densely populated areas has been a constant historical factor in human settlements. Most cities are located in the valleys, flood plains and the coasts. Cities through their nature of having large impervious areas produce large run-offs which the drainage network cannot accommodate, and are potentially exposed to floods. It has been acknowledged that the damage potential of floods in the cities is extraordinarily high. Given the high population density in urban areas, even small scale flash floods may cause considerable damage. At the extreme end of the disaster spectrum, urban flash floods can result in disasters that set back development drastically. With climate change and global warming resulting in increased frequency of flood s and their magnitude, continuing urbanisation and disproportionate growth, the economic costs of flash floods will soar. Sustainable management of urban flood risks is becoming an increasingly challenging task for city/municipal authorities. (ii)
Flash floods are distinctly characterized by very swift rise and recession, associated with debris flows and landslides, occurring along channels and rivers with small drainage area. Their distinct features paint a stark picture. Flash floods happen suddenly, easily and frequently, are very destructive, and difficult to protect against. Of late, flash floods brought extremely destructive disasters e.g. the recent flash floods in Istanbul, Turkey. In most cases it involves a break in flood protection facility.
Rapid economic growth aggravates flash flood hazards. As new construction takes over arable land, and urban population density increases, infrastructural growth may not proceed in tandem. Growth in urbanization inevitably reduces vegetation, wetlands and other habitats for flood prevention.
The patterns of urban flash floods are almost identical in its force. Small streams, canals, channels, and drainage ditches become fast flowing dangerous rivers. Where the terrain is flat, primary and secondary roads are inundated with torrents of floods, streets and parking lots becoming rivers of moving water. As the connotations imply, flash floods rise rapidly within a few minutes or hours of heavy rainfall. As the water rises rapidly and moves swiftly, carrying cars, ripping trees from the ground, and even destroying roads and bridges.
Disaster risk reduction in identified potential flood prone areas need to focus on extent of exposure and vulnerability. Exposure of urban dwellers close to river streams including infrastructure (roads, bridges, dams, power houses) located in the same area requires greater attention. Vulnerability could be minimized through increasing preparedness by way of flash flood guidance, community awareness campaigns, early warning systems, and planned coordinated emergency procedures. The World Conference on Disaster Reduction held in Kobe in January 2005 called for the early warning system to be people centred, providing timely and reliable warning to the people at risk.
While generally natural occurrences, flash floods are increasingly the result of human activities or poorly designed infrastructure. Very few countries have flash flood management action plan. Among those that do, China stands out with severe penalties for negligence. Flash floods are frequent features in China with two-thirds of the Chinese territory being mountainous, the recurrent natural disasters compounded by monsoon climate, fragile mountain terrain and increasing human activity. The threat confronts a total of 74 million population exposed to flash flood hazards in the mountain region. In a period of four decades (1950-1990) a total of 225,000 died in floods in China. (iii) The action plan calls for approval of any new construction in urban planning contingent upon completion of a flash flood assessment.
Prior to approving construction projects, city/municipal authorities could examine conditions affecting the construction area. Best practices in the management of flash floods in urban areas warrant enhancing the disaster management chain and assuring these extend into urban planning. Among some authorities, the approach include helping municipalities prepare for climate change. (iv)
Else where, like in West Africa, there’s a growing awareness that “urban surge feeds flooding”, if left unplanned and unorganized, that is. Dakar’s suburb of Guediawave was a dry area 30 years ago. Nowadays, it’s a different story. The residents of this densely populated suburb endure floods every rainy season. (v) Explosive population growth, poor urban management, urban congestion, and indiscriminate building in green belt zones all add on to shortening the fuse for disaster. Overpopulation in northern Nigeria has people building homes on waterways, and natural drainage system becoming blocked by rubbish. Despite bans on construction in the Dakar “cap vert” wetlands, this flood prone area received waves of rural-urban migration in the wake of the 70s and 80s Sahel-wide drought. Now the region is full of buildings and roads which block natural waterways and basins.
References:-
(i) Todays Zaman. Klaus Jurgens. The limitations of urban development: Have we reached the limitations of urban planning?
(ii) The Associated Programme on Flood Management (APFM).
(iii) Flash Flood Management in Urbanizing China, Xu Jianchu and Li Zhuoqing, Kunming Institute of Botany, the Chinese Academy of Science
(iv) Prediction and management of flash floods in urban areas (URBAS), Thomas Einfalt , Andreas Wagner, Fritz Hatzfeld, Jörg Seltmann
(v) IRIN, West Africa, Urban surge feeds flooding, Dakar, 14 September 2009
