Landscape Based Stormwater Management Design Solutions for Residential Areas: The Case of Two Selected Sub-cities in Addis Ababa, Ethiopia
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Date
2021-06
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Addis Ababa University
Abstract
For decades, Addis Ababa has gone through several changes for its built environment, while it is having a
dramatic increase in population which has given rise to extension and densification of the built-up areas
of the city. Such changes of the natural landscape, lead to flooding becoming eminent. It is common to
see drainage problems in old and new housing areas where residents rely on storm drains to carry a
large amount of runoff generated from their compounds, where stormwater mitigation strategies are
neglected on an individual plot level. Hence, on-source control of stormwater, which entails application
of stormwater mitigation strategies in residential spaces (which are one of the major sources of
stormwater) is essential.
Hence, to assess Landscape stormwater management (LSM) Technologies on individual plots of the
residential areas of Addis Ababa, both qualitative and quantitative research methods were employed,
while both primary and secondary data were collected. Moreover, the study areas selected for this study
were Lebu Varnero watershed area from Nefas Silk Lafto Sub city and Dera Sefer watershed area from
Arada Sub city. Different data collection methods such as field observation, questionnaires and
interviews were employed in this study.
The results showed Impervious surfaces (including both built-up areas and streets) were observed to
cover much of both study areas, and the study results showed that land use and size, imperviousness, soil
type, precipitation (rainfall), current drainage conditions and slope were the major factors that affected
stormwater runoff in residential plots and the applicability of Green Infrastructure practices. Stormwater
mitigation mechanisms such as Permeable pavement, Grass Paving walkway, Rain Barrels, Lawn covers,
Evergreen trees were used in the design to help control urban stormwater runoff problem in residential
plots. In addition, Landscape stormwater management strategies such as a Stormwater tree, Bio
retention Ponds, Road Side Vegetated Swale, Green Gutter, And Previous Driveway and Walkways were
used in the design to alleviate stormwater runoff problems in the surrounding open spaces in the
neighborhoods. These mechanisms proposed to handle stormwater are estimated to decrease the
stormwater runoff by an amount of 0.48777246 m3
and 0.377122032 m3
per one hour of rainfall for the
specific plots selected from Lebu Varnero apartment and Dera Sefer study areas respectively.
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Keywords
Stormwater, Green Infrastructure, Landscape based stormwater management,, on-source stormwater control