Accessing the impact of land use change on the flooding of Kiwunya channel in Kampala
Barigye, Grace Stuart
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Kiwuunya channel stretches from UCC church Nakulabye to Northern By- pass, Bwaise. It passes through Kasubi which is predominantly a built up area comprised of settlements and commercial buildings. This has led to continuous infrastructure development leaving an ever increasing extinction of green area cover. As a result of which there is an increase the volume of surface runoff associated with the increase in paving and construction of new buildings. The steep sloping topography of the Kiwuunya sub catchment in Kasubi increases the dynamic properties and the erosive capacity of the surface run off and this leads to the siltation in the downhill streams, channels, culverts and other storm water conveyance conduits. These are the main storm water management systems present, once blocked result in flooding of the areas downstream. With the above mentioned problems, coupled together with their direct and indirect effects, it is of great relevance that complementary storm water management measures that economize space and are not destructive to the environment be researched, examined and be implemented to give additional storm water management capacity. This necessitates the need to research in the direction of Sustainable Urban Drainage Systems (SUDs), which control floods in a natural way through temporary storage and slow release onto land. There are several examples of these among which are the not so popularly used, detention ponds. Hence the research is aimed at maximizing the potential use of these structures in urban areas, owing to their good space economics, inexpensiveness and ability to retain and potentially release a significant volume of runoff. The report also gives the different methodologies that were undertaken during the research, such as obtaining of rainfall statistics of the area to be able to estimate the volume of runoff generated as well as assessing how the change in land use categories has and will affect the flooding patterns of this channel. This information was then used to design detention ponds for temporarily storing runoff. The conclusion to the report majorly presents recommendations of maximizing the use of sustainable remedies for controlling rainfall runoff, based on the key findings which included, low permeable soils present, fairly available unpaved land and that installation of such structures can produce a percentage runoff reduction of at least 33% at the study area.