The potential of roof catchment as a flood management strategy at Mavoko sub-county in Machakos County
Ndonye, Christine Musyawa
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The traditional approach for coping with urban flooding has been linear whereby all the rainwater that has fallen over a wide area is conveyed to and managed by sewers or rivers lines. When the carrying capacity is insufficient, possible counter measures are considered only to the line; denoting the upsizing of the sewer, widening of the rivers or increasing the pumping capacity. Due to heavier and unpredictable rainfall, the water conveyance system in the whole sub-county is limited, thus requiring upgrading of another method of containing the excess water. The water management approach worldwide is currently in transition, with a shift evident from purely centralised infrastructure to greater consideration of decentralised technologies, such as rainwater harvesting (RWH). Initiated by recognition of drivers including increasing water demand and increasing risk of flooding, the value of RWH is beginning to filter across the academic-policy boundary. However, in Kenya, implementation of RWH systems is not straight forward due to social and technical barriers, concerns and knowledge gaps exist, which currently restrict its widespread utilisation. (Ward, S., Butler, D., Barr, S. and Memon, F.A. 2009) Rainwater harvesting as a supplementary source of water has not received any serious attention. This research investigates the potential of roof catchment collection, storing and using rainwater in Mavoko sub-county, Machakos County. The importance of this study lies in severe flooding in some areas of Mavoko particularly in its satellite town which are experiencing rapidly population and development growth in the sub-county. So many people are affected when floods occur and furthermore the current water supply system is not adequate to provide enough water for the growing population. vi Mavoko has a tropical climate, with rainy months from March to May and October to December, with approximately 118 days of rain in the year and an annual precipitation of 40 inches (Kenya Meteorology Department, 2011). Considering the chronic water scarcity in the sub-county, a considerable amount of homes have elevated or underground water storage tanks installed to provide water for their daily use. These two observations make rainwater catchment systems a great option to be considered because the approach takes advantage of the opportunities the town’s climate as well as existing infrastructure.