DESIGN OF A STORM WATER DRAINAGE AND HARVESTING SYSTEM. CASE STUDY: MACHAKOS TOWN CBD.

Machakos town has had continued growth. It currently has an estimated population of one
million people and great economic potential therefore there is need to set up infrastructure to
sustain it. One of the major requirements for any successful urban area is a good water supply.
Unfortunately the town faces major water scarcity problems and therefore water rationing is the
norm. The storm water runoff is commonly treated as waste and discharged into rivers and
municipal sewage systems yet it can be used for non-potable purposes.
To provide additional support, storm water harvesting is an opportunity for any town in an arid
and semi-arid region. Once the rain falls onto the impervious surfaces of the streets, sidewalks,
buildings and parking lots it picks up any and all pollutants that are in its path, gathering volume
and speed into the preexisting storm drains .It is important to also note that the town is currently
upgrading the drains therefore there is an opportunity to harness water which is a precious
resource.
This design project will mainly involve the harvesting of the water flowing through the drains of
the CBD and developing recommendations on how best to design. Using GIS techniques the
runoff potential of the study area (Machakos town CBD) will be done by capturing the potential
catchment surfaces and subsequently calculating the amount of runoff that can be harvested from
these surfaces. From the results so acquired, the conveyance channels for the storm water
collection and the storage reservoir will be designed and sized. The conveyance channels will be
assigned litter traps and a sediment removal section is to be included before flow into the
underground tank reservoir. The design will be limited to harvesting and storing the water and
recommendations will be done on how to treat the water using different ways.
In general this design project focuses on the forgotten infrastructure of Kenya since in the past
little or no focus was placed on drainage systems.

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UNIVERSITY OF NAIROBI final report..pdf6.24 MB