Characterizing hydrological-sensitive areas of the Kinyerezi river sub-catchments in Dar es Salaam, Tanzania using the topographic index approach

Abstract

Several areas experience frequent floods due to anthropogenic activities. Among them, is the Dar es Salaam city, which experiences frequent floods along the Msimbazi River, whose flows originate from different tributaries including the Kinyerezi River. This study aims to evaluate the hydrological-sensitive areas of the Kinyerezi River sub-catchments using topographic index values (λ*) that enable the identification of areas with a higher probability of generating surface runoff. A digital elevation model was utilized to delineate the Kinyerezi River sub-catchment characteristics using ArcGIS 10.4. Soil infiltration rates (Ks) on selected open places were determined using a Guelph permeameter. Soil particle size distributions were analyzed and the λ* values were evaluated. The results showed the particle size distribution contains sand and silt-clay ranging from 46 to 84% and 16 to 53%, respectively. The Ks ranged from 0.6 to 7.8 mm/h while the sub-catchment KS3 scored the highest λ* value of about 10.7. Hence, there is a higher probability for generating surface runoff. Sub-catchment KS16 scored the smallest λ* value of 5.7, perceived to generate less surface runoff. Low-impact development practices capable of capturing runoff and enabling infiltration, evaporation, and detention should be employed in sub-catchments with higher λ* values. HIGHLIGHTS The study improves knowledge and awareness of the sensitive sub-catchments of the Kinyerezi River catchment.; The soil infiltration rate ranges are given for the Kinyerezi River sub-catchments and can be adopted by engineering practitioners in the design of stormwater management infrastructures in the catchment.; Gives the gravel, sand, and silt-clay contents for soils from the Kinyerezi River sub-catchments that may help engineering practitioners in deciding the type of stormwater management to adopt for the catchment.;

Keywords

• guelph permeameter
• floods
• infiltration rate
• kinyerezi river catchment
• surface runoff
• topographic index value