Assessing the effectiveness of grass cover as a run-off mitigation measure in the urban landscape

Abstract

This study was aimed at investigating the effectiveness of grass cover of various types as a runoff mitigation measure in the urban landscape with Makerere University, Kampala, Uganda as a study area. It was carried out during the period March to august, 2022 and mainly focussed on the unpaved (grass covered) areas (67% of total area) within the study area.

Surface runoff was collected from constructed runoff (or erosion) plots which were constructed offsite on which field conditions were reproduced for experimentation under different grass type covers, slopes and simulated rainfall intensities: This was guided by rainfall data collected from the Makerere University weather station and the soil results analysed from the Makerere University Highway laboratory. Surface runoff volume was measured and coefficients of runoff obtained for the different grass cover types and for bare soil as the control.

The results from the investigations were tabulated and graphed and analysed, and it was observed that the Grass Covered plots generally produced on average 3 times less runoff compared to the bare soil plots for more or less all slope conditions and rainfall intensities. It conclusively showed that grass cover is a very effective runoff mitigation measure in comparison to bare soil, and as such it is highly recommended as a landscaping choice in opposition to paving which would otherwise covert nearly all rainfall received into runoff