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ABSTRACT
Rapid
development has changed the land use and this will lead to an increase
in the surface runoff caused by the increase of the impervious surface
area. Impervious surface
area will transform most of the rainfall directly as surface runoff.
Hence a given rainfall now produces significantly more runoff
volume then before.
Stormwater
management in urban areas has changed from rapid conveyance approach
to control at source that states
the post development and pre-development peak flow should be
the same. Department of Irrigation and Drainage has introduced Urban
Stormwater Management Manual (MSMA) and directed all the new
development should follow this new regulation.
This regulation seeks that the quantity and quality of the
surface run-off should be similar for the post and pre-development.
A
numbers of Best Management Practices (BMPs) have been developed to
control the quantity and quality of the surface run-off.
Examples of the BMPs are wet pond, dry pond, swale, wetland and
infiltration system.
The
drainage system in Engineering Campus Universiti Sains Malaysia that
used the control at source approach was chosen as the research site.
Bioecological Drainage System (BIOECODS) is a pilot project
that applied the control at source approach as described in MSMA. This
research aims to evaluate the BIOECODS as one of Storm Water
Management applications in Malaysia.
The
implementation of the research requires a comprehensive data
collection such as rainfall depth, velocity and discharge in the
surface and sub-surface swale. The analysis of the data shows that
BIOECODS has functioned as designed. Emptying time of ecological swale
less than 24 hours is recorded in the surface and sub-surface swale
after a rainfall event. Peak flow and volume attenuation also occur at
surface and sub-surface swale. However the percentage of the
attenuation depends on the ARI. The study of the dry pond indicates that emptying time of the
dry pond also depends on the ARI. From the study the dry pond has
emptying time less than 24 hours when the rainfall event is less than
2 year ARI.
Hydraulic
simulation of BIOECODS using Storm Water Management(SWMM)
computer model showed that peak hydrograph could be attenuated
to the pre-development hydrograph. Calibration process result shows
that SWMM model can simulate well in term of peak hydrograph rather
than volume.
From
the quality aspect, grab
sampling results show that water quality at outlet type C achieves Class II A standard.
The value of pH ranges between 6.5 –7.7, Dissolved Oxygen
between 5.74-6.4 and BOD between 3-6 mg/l is within the range of Class IIA. The
existence of heavy metal is too little and the value of phosphate and
total phosphate between 0.02-0.03.
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