تقييم استخدام البنية التحتية الخضراء لتحسين إدارة مياه الأمطار في محافظة المثنى

Evaluation of Using Green Infrastructures for Improvement of Stormwater Management in Al-Muthanna Governorate

Abstract

Stormwater surface runoff and its inflow to sewer systems have increased lately due to vast urbanization, climate change and aging of existed infrastructure, thus led to the occurrence of floods.
This study defines the using of stormwater management model SWMM for predicting the stormwater quantity resulting from the surface runoff into the sewer system during rainfall events at different return periods as well as applying low impact development (LID) on the municipal separate storm sewer system (MS4) of Al-Soob Al-Kabeer quarter, also redesign MS4 by changing diameter of trunk line.
Also, a solution to reduce the quantity and improve the sewer system during rainfall events was suggested. The quantity of MS4 discharge model was manually determined by altering the effective sub-catchment features using design flowrates and simulated flowrates.
Values of average normalized of mean square error (NMSE) (1.0145) and average coefficient of correlation R (0.957) were within the acceptable boundaries and confirmed the validity of the model. Results of the quantity model indicated that the system was at critical conditions and flood might happen during wet weather, high flow rate into many manholes.
As a response to rainfall event, when the return period increased from 2 to 25 years showed a raise in MS4 flooding volume and flooding manholes ratio from 1466 m3 and 10% to 13731 m3 and 42%, respectively.
The proposed solution of LID was compared to without Added LID, it reduced the volume flooding at different return periods 2,5,10 and 25 to 998, 2292.4, 7959, and 11967, respectively, while the other proposed solution of redesign of stormwater sewer system by changing the diameter of the trunk line was compared to without changing diameters, reduced the volume flooding at different return periods 2,5,10 and 25 to 1084.5, 2003, 7375, and 12546, respectively.
When comparing between the two solutions, the preference is given to LID technically and construction point in reducing the flood.