Assessment and Modeling of Urban Drainage System Performance (A Case Study of Mojo Town)
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Date
2020-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
The drainage system is one of the most important factors to be considered in the urban
drainage infrastructure plan. Now inadequate urban stormwater drainage problems
represent one of the most common sources of compliant numerous towns of Ethiopia.
Drainage problem in mojo town the worst issue of over flooding on the surface runoff at
high rainfall season. This difficulty occurred due to inadequate drainage network
infrastructure and the increase in the urban pavement on most urban sub-catchments. The
objective of this study to identify the critical condition and related problem with a drainage
system, assess the hydraulic performance of stormwater drainage infrastructures, and to
evaluate alternatives for drainage problem mitigation measures are achieving this specific
objective SWMM5.1 model and LID control was used in the study. The calibration and
validation of the SWMM5.1 model well-done and its performance was tested by the
goodness of fit using the coefficient of determination (R
2
) =0.97, the Nash –Sutcliffe
coefficient (NSE) =0.96, and Relative error (RE) =11.16%. The simulated area of the study
subdivide to four outlets of the total area of sub-catchment is 745.2ha joint to drainage
system infrastructure of 93 nodes, 101 channels, and one divider are simulated by SWMM
5.1 model. From model result greater than 60% of drainage infrastructure is flooded, at the
outfall total sub-catchment runoff is 6.88m
3
/s average flow, 22.44m
3
/s maximum flow and
3
583.07*10
3
m
total volume of all outfall. The LID control used in this study for reduced
the peak runoff overflow and select the best alternative on the outlet one of the project in
the same sub-catchment S1, S2, S3, S5, S6, S9, S10, and S12 were the reduced the total
outlet one volume by 28.12% using bio-retention Cell scenario, 25.9% infiltration trench
scenario, 26.71% using permeable pavement scenario and also on sub-catchment reduced
total volume outfall one reduced by 3.02 % using vegetation swale scenario. All scenarios
used two of the highest value of runoff decreased by Bio-retention Cell scenario and
permeable pavement for total study applied. by using two selected Lid control total volume
of all outfall from 583.07*10
3
3
m
is reduced to 425.89*10
3
3
m
by 36.92% from the total
study. Generally, the mojo town urban drainage system performance infrastructures
overflow assessed and controlled for the problem occurred using the best alternative
mitigation measures by improved LID control for all study areas.
Description
Keywords
Drainage systems, SWMM5.1, performance, LID, alternative mitigation