Due to poor drainage, heavy rainfall often causes untold damage to property, power outages and sometimes loss of human life.
Rapid urban development combined with impacts of climate change, which make some areas drier and others wetter with intensified rainfalls, have further compounded the flooding menace.
While acquiring a piece of land, especially in an urban set up, apart from considerations such as good infrastructure, water availability, electricity and proximity to social amenities, not many people think about the terrain and drainage, which may predispose an area to flooding.
The cost of damaged homes and production facilities is too high overlook. Although sewer and drainage systems require large investments, installation and maintenance costs can be reduced by planning and incorporating innovative solutions.
One such solution is the application of Geographic Information Systems (GIS) to first assess at the general topography of the area. This requires the elevation of the area, which normally is called Digital Elevated Model (DEM) as the base to all other existing infrastructure such as buildings, roads and other urban facilities.
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From the DEM, contours that show areas of equal elevation in the urban area can be generated.
With the DEM as the base for all other topographical features, a GIS can delineate areas that are likely to flood.
With some given input parameters that are related to flooding in a given area, the tool then computes and gives an output in form of flood risk maps that will show areas or zones that are likely to flood during heavy storms and those that have a low risk of flooding.
This information will be useful in making decisions. This includes developing new drainage systems that will decrease the risk of possible flooding or even moving the people living close to a flood risk zones.
Also, with the availability of meteorological satellites up in space, Kenya is on its way to realising real time weather prediction. Satellites send information regarding possible El Nino, drought or a heavy storm before it occurs hence creating awareness before time. Although there is already digital elevation data for the entire earth, which is commonly referred to as Shuttle Radar Topography Mission, it is not very accurate and therefore not reliable for mapping elevation for a small region like the city of Nairobi.
The meteorological department can use forecasting systems that give accurate information regarding flooding. The warning system could be made in such a way that it monitors water levels in real time. By combining this information with general weather forecasts, the risk of saturating the sewers resulting in flooding can be predicted.
GIS and GPS also helps in locating sewer lines routes and drains.
— The writer is a consultant in Geoinformatics and lecturer at JKUAT