Sustainable Urban Drainage Options for Mekelle City
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Date
2018-03
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Publisher
Addis Ababa University
Abstract
Flood generation became a common incident in Mekelle because of low vegetation cover and the vastly
spreading land cover that accompanies development also results in less water being available for
infiltration into the ground. Moreover, the increasingly constructing impervious structures facilitate
more flood to be produce and overloading the conventional system of drainage in the city. Therefore,
the existing flooding impacts on the conventional system studied and parameterized with help of
Geographical information system (GIS) application.
The paper also presents a diverse stormwater management technique that potentially could be
implement in a case study area and evaluate their sustainability using Analytical Hierarchy Process
(AHP) decision support tool. Five alternatives for stormwater management in the selected site
evaluated according to 4 main criteria and 11 sub criteria using an Analytical Hierarchy Process
type called MCDA model. The model, which applies quantitative scoring and experts invited to
conduct the scoring and weighting elements of the method. Again, SWMM tool is applied to
compute the rainfall-runoff simulations with in Subcatchments located in the city of Mekelle
(Northern Ethiopia).Finally, comparisons takes place between different Hydrologic and hydraulic
parameters produced by a design storm before and after installing SWMM-LID control
components.
The result showed that the best sustainable stormwater management solution after analysis of the
Multi Criteria Analysis weightage tends to Rain garden (A2), and infiltration trench (A3) with
overall aggregate weight of 0.489 and 0.232 respectively which employs main criteria such as
technical, Environmental impact, social impact, and economic impact. Following weightage for
the best management types a moderate-weight to Bio-cells (A1) scoring 0.190, 0.18 to Vegetation
swale (A5) and finally lowest priority of 0.166 to Permeable pavement (A4). With installing of
LID-controls that displace equal amount of area covered by impermeable ground, runoff on
affected Subcatchments S80 & S81, high imperviousness, with initial flow rates of 3.16m
3
/s and
3
3.34 m
/s respectively reduced and controlled. As recommendation, some relevant LID-
components are allocated considering the suitability criteria of construction of different site in
Mekelle city.
Description
Keywords
urban drainage, Flood generation, GIS, Mekelle City, Analytical Hierarchy Process (AHP)