Urban Risks Flash Floods
Posted: Wednesday, September 23, 2009
by M E Reza
http://mereza.wordpress.com/
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)
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, Jrg Seltmann
(v) IRIN, West Africa, Urban surge feeds flooding, Dakar, 14 September 2009
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Top-level comments on this article: (2 total)Good article, M E. I live in an area of the world that can have torrential rains and hurricanes. The planning is pretty good, most new areas of construction have draining to retaining areas in the event of a flood. Welcome to SearchWarp.Thanks Lorrie. Wherever we are, our lives interact with the environment. If we do not maintain harmony and balance with our environment, nature strikes back with vengeance.
Hi M E Reza.Manila, the capital of the Philippines is noted for flooding due to inadequate drainage. An hour of downpour will cause immediate flooding in the area.In November 1991 typhoon Uring devastated my hometown in the Philippines. A flash flood killed approximately 6000 people and crop and property damage so immense. It was due to massive deforestation. The Japan International Cooperation Agency (JICA) implemented a Flood Mitigation Project that addressed the threat of flooding during typhoons and heavy downpour, water control canals have been created.Thanks for sharing this well-written and informative article.Welcome to the Searchwarp Community of Writers.Sincerely,NenitaThanks Nenita,It's good to hear of flood mitigation measures being undertaken somewhere to address the threats. Factors contributing to the flash floods are diverse. Massive deforestation, illegal logging, poor urban planning etc. - the common threads being indiscriminate activities which upset the balance. When nature loses its equilibrium, hazards turn to disasters.
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