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Urban flooding - Dire Dawa city Example

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Dire Dawa is the second largest city in Ethiopia situated in the eastern part of the nation. Dechatu river crosses this city dividing it almost equally into the east and west portions. The river rises from the Ahmar Mountains and flows north towards the larger, and mostly used for irrigation, Awash river.  Even if the Dechatu flows towards the Awash river, it does not visibly empty into Awash river, rather it loses itself in the Cantur plain (Buren Meda) north of the city. 



  Figure 1. Dechatu river crossing Dire Dawa town dividing the city in to eastern and western portions. 



Flash floods in urban Dire Dawa, Ethiopia happened many times in different years. In 2006 alone, 256 people reported to have lost their lives, 244 people disappeared, 10,000 people displaced, and houses, infrastructure, and livelihoods were damaged (ETV and VOA news,  2006).





  Figure 2. Asphalt road in the middle of Dire Dawa town being damaged by flash flood that had happened in August, 2006 (ETV news, Augest 2006). 

Part of the observed flood damage was caused by socio-economic factors, such as the increase in population and wealth around the river, as well as changes in terrestrial system, such as urbanization and deforestation, that have led to the loss of wetlands and natural floodplain storage (e.g. via dike construction, river straightening and floodplain sedimentation). Changes in climate may also have strong contribution (Feyen et al, 2010).
Climate models indicate that climate change also plays an important role in exacerbating flood problems all over the world. 
Projections show that global warming will intensify the hydrological cycle and increase the magnitude and frequency of intense precipitation. This may increase flood hazard triggered by intense rain, particularly the occurrence of flash floods.
Floods are microscale to mesoscale climatic phenomena. Hence, large scale flood analysis using water resources, average flow conditions, and changes in seasonal runoff alone are not enough. Projections of  rainfall variability over the seasons and years using regional and micoscale modeling is required.
In this regard, I am working on regional and microscale models to have clear knowledge of climate and land interactions contributing to flood events in Dire Dawa and will inform you as soon as I will have the results ready.

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