Climate change, urban flooding and urbanization

Urban development may encourage people to move to cities. There are unprecedented benefits attributed to urban life. Better schools for the children, health facilities, and transportation are few that comes to mind immediately. Urbanization, if not planned well, has its own bad consequences. The IPCC report (2013), predicts that there will be extremes of climate like flooding, drought and storms. In connection with these effects of climate change, arbitrary urban planning only for the sake of urban development without consideration of those extremes of climate may lead to disaster.

Urban flooding can easily occur due to ignorant urban development. It happens when water flows faster to urban region when there is no or little infiltration into the soil and surface obstacle that can hinder its rapid movement. There should be well built dikes, channels, and domes to protect water from flowing into the cities. Hard tile pavements, continuous asphalt, close to each other buildings result in less water infiltration into the soil. Too close buildings in real estates are examples. If these real estates are located at high level urban areas, the water infiltration will be highly reduced at the high lands. This causes flash floods which are highly faster and disastrous to people, homes, and animals dwelling in the lowland urban area. Some people also build asphalt or cover the bare land with different impervious pavements for different purposes. Governments should regulate what and where one can build so that infiltration would be optimum.

In Ethiopia, there were damages due to flash floods. In 2006, Dire Dawa, the second largest city experienced unprecedented damages due to flash flood ( Urban flooding - Dire Dawa city Example). It occurred twice in the same year. Poor urban land use resulted in less land cover and hence rapid surface run-off. The sand soil around the Dechatu river, the river which crosses the city dividing it into almost two equal parts, is also partly to blame. The city sewage system and draining canals did not have the necessary capacity to drain away the large amounts of rain that fell in a short period of time. In the coming years, the same would happen if these problems remain unsolved.

It is pretty obvious that urbanization is on the increase. Common consequences of urban development include the removal of vegetation cover and an increase in impervious surfaces and drainage networks, all of which increase precipitation runoff into streams and rivers. In addition to this, there may be an increasing precipitation which may increase urban flooding.

Urban development plans need to harness weather and climate forecasts. Expertise that perform appropriate model setup that employ climate and weather projection simulations is needed. The plan also needs to explore appropriate storm water conveyance systems, terraces, dams and other preventive systems.

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