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Synopsis:
Grassed
swales
refer to a series of vegetated, open channel practices that
are designed specifically to treat and attenuate stormwater runoff for a
specified water quantity volume.It
specify as beneficial alternatives to concrete gutters for stormwater
management due to their advantages of infiltration and filtration of
stormwater.
As stormwater runoff flows through the channels, it is
treated through filtering by the vegetation in the channel, filtering
through a subsoil matrix, and/or infiltration into the underlying soils.
There are many
design variations of the grassed swale, including the grassed channel, dry
swale and wet swale. The specific design features and treatment methods
differ in each design, but all are improvements on the traditional drainage
ditch. Each incorporate modified geometry and other design features to use
the swale to treat and convey stormwater runoff.
Grassed swale
in Engineering Campus, Universiti Sains Malaysia (USM) is a part of the
pilot project of Bio-Ecological Drainage System (BIOECODS) which include of
perimeter swale and ecological swale. This research study will focusing in
the implementation of the Best Management Practice (BMPs) in a drainage
system especially on constructed grass swales. Six locations (Figure 1-6) of
the constructed swale as illustrated in figures below, will be used as a
field study area.
Figure 1 : Clinic (Site 1) |
Figure 2 : Chemistry School (Site 2) |
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Figure 3: Civil School
(Site 3)
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Figure 4 : Aerospace School (Site 4)
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Figure 5 : Mechanical School
(Site 5) |
Figure 6: USM Hall (Site 6) |
There are 2 types of ecological swale that includes in this study which are :
i .Ecological Swale - Type A
Cross Section of Swale - Type A
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Swale Type A in Dry Period
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Swale Type A in Wet Period
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ii. Ecological Swale -Type B
Cross Section of Swale -Type B
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Swale Type B in Dry Period
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Swale Type B in Wet Period
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There are several methods for determining Manning n in vegetated channels.
These methods recognize that the physical characteristics and growth
patterns of vegetation are important factors in evaluating hydraulic
resistance.
The objective of the study is to develop a set of equations to calculate the
hydraulic resistance and to determine the stability of vegetation in swale
channel.
To achieve these objectives, the field
study through these six location, concerning stage-discharge, flow
resistance, bed forms and flow structures will carried out in a vegetated
grass swale channel.
This study is also to investigate how density and arrangements of vegetation
influence stage-discharge, flow resistance, bed forms and flow behaviours.
The collected data such as rainfall, flow, depth of flow, slope, grass type,
length of swale and sampling time from October 2009 until 2011 will analysed
and tested. Methods and procedures will developed using three mowing type of
grass height to quantify both geometric and biomechanical properties of the
plants when determining the vegetation resistance. A new set of equations
will provide a basis by which to quantify hydraulic resistance and stability
of vegetation in swale.
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