Investigating the adequacy of drainage systems on newly upgraded roads. A case study of Lukuli road in Kampala district.
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This dissertation presents results of the investigation of the adequacy of the drainage system on newly upgraded urban roads with a case study of Lukuli road, and proposed mitigation measures based on Road Design Manual Volume II: Drainage Design 2010, Kampala Drainage Master Plan 2016 T2. The drainage system is to prevent onsite water standing on the surface and convey the offsite storm runoff from one side of the roadway to the other. An efficient drainage system is therefore essential to allow water to flow off and away from the road as quickly as possible. Lukuli road drainage system is not properly functioning. The primary data were photographs that show the current drainage system conditions, site visit, field survey and questionnaires that were gathered from the engineer, residences and road users about the performance of the drainage systems during the rainy season. The important secondary data for this research were land cover map, DEM data, rainfall data, and design data. Hydrological analysis was carried out by using Rational Method. The inadequacy of drainage system during the rainy season to pass the flood, implementation was not as per design hence inadequate culvert capacity, absence of inlets at appropriate points, lack of proper maintenance and poor disposal of solid wastes into the culverts are some of the reasons for poor performance of the system. The design peak discharge calculated for the different catchments along was based on the return period of 25 years but verified using 50 years return period. The calculated review discharges at chainages 0+916, 1+440, 1+480, 2+960, 3+959, and 4+420 were big compared to the existing culvert capacity hence flooding in those particular sections. Therefore, before the culverts are constructed, the design and the review data must be checked always during the design stage. It must be the design peak discharge to be greater than the review peak discharge to control the floods that over follow on the road. At chainages 0+916 and 1+480, the design peak discharge was greater than the review flow but the implementation was not as per design. The drain suffered from low capacity, soil accumulation, the absence of inlets, lack of proper maintenance and disposal of solid waste into the drain and the crossing culverts. The designer and contractor should follow the minimum requirement set by the Ministry of works and Transport regarding the drainage structure, size, length and alignments of road drainage structure, and strict supervision by government officials and consultants during implementation so as to prevent the impact of poor drainage on the road pavement.