International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 400-409 Article ID: IJCIET_10_04_043
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=04
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
Scopus Indexed
STORMWATER DETENTION IN ROAD
SHOULDER USING STORMPAV GREEN
PAVEMENT SYSTEM
Zi Sheng Lui
Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak,
94300 Kota Samarahan, Sarawak, Malaysia
Darrien Yau Seng Mah
Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak,
94300 Kota Samarahan, Sarawak, Malaysia
Fang Yenn Teo
Faculty of Engineering, University of Nottingham Malaysia Campus, 43500 Semenyih,
Selangor, Malaysia
ABSTRACT
Computational Fluid Dynamics (CFD) is applied on StormPav Green Pavement
system as combined road shoulder and stormwater detention structure. Applicability of
the system is tested by simulating flow through the multiple chambers within StormPav
system via road curb-opening inlet and outlet. The CFD simulations demonstrate flow
patterns resulted from 5-minute 10-year ARI design rainfall. The distance of inlet and
outlet is found to play a major role in the flow pattern in the StormPav system. The
further the outlet away from the inlet, the more the CFD simulations show flow
trajectory plots that suggest a water mixing quality. This finding is interestingly point
to a self-cleansing ability in the StormPav system that suggests the flow pattern is
favourable to flush out sediments carried by stormwater from roads.
Keywords: CFD, On-Site Detention, SolidWorks, StormPav, Stormwater.
Cite this Article: Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo,
Stormwater Detention in Road Shoulder using Stormpav Green Pavement System,
International Journal of Civil Engineering and Technology, 10(4), 2019, pp. 400-409.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=04
1. INTRODUCTION
Stormwater detention structures are one of the human interventions to the urban hydrological
processes to reduce the volume of running water in the built environment [1-2]. Pertaining to
http://www.iaeme.com/IJCIET/index.asp
400
editor@iaeme.com
Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo
urban road drainage, surface runoffs generated from road surfaces are directed to stormwater
detention structures, in which parts of the running waters are trapped and stored within over
the course of storm events. Some of the examples are infiltration trench, pervious road
pavement, vegetative swale and rain garden that are adjacent to roads (see Figure 1). These are
hence the control-at-source approaches [3] so that running water could be controlled near its
source and less water being discharged to water ways.
(a) https://www.stormwaterpa.org
(b) https://ascelibrary.org
(c) https://prj.geosyntec.com
(d) https://phys.org
Figure 1 Stormwater detention for urban road drainage, (a) Infiltration trench, (b) Pervious road
pavement, (c) Vegetative swale and (d) Rain garden.
Infiltration trench in the figure is filled with aggregates, in which the voids between the
small stones could store stormwater. Pervious road pavement is laid with a layer of pavers that
the joints between them allow water to infiltrate to the underlying layer. Vegetative swale and
rain garden, on the other hand, are filled with porous media that is able to absorb stormwater.
In a study in Malaysia [4], a function of stormwater detention is integrated with road curb
system as depicted in Figure 2. The researchers present a way to capture the road runoff within
a manmade chamber that connects to the road curb-road shoulder structure and stormwater
inlet. Otherwise, running waters from the road are normally discharged to urban drains directly.
Extending from the above-mentioned project, this paper is intended to improve the structure
further. We are introducing StormPav Green Pavement System as an alternative construction
method to create the stormwater detention chamber [5].
http://www.iaeme.com/IJCIET/index.asp
401
editor@iaeme.com
Stormwater Detention in Road Shoulder using Stormpav Green Pavement System
Figure 2 Existing road drainage system and proposed stormwater detention [4]
2. STORMPAV GREEN PAVEMENT SYSTEM
StormPav consists of precast concrete pieces which a hollow cylinder piece is sandwiched
between two concrete plates to make up a single modular unit. The units are made of G50
concrete specially designed to withstand up to 10 tons of loading [6].
The hexagonal plate is used as top and bottom covers, in which the former functions as
road pavement with service inlet to drain stormwater; and the latter functions as a base with
service inlet to allow infiltration. The surface area on a single plate is 0.1624m2 with a service
inlet of 0.04m in diameter. Height of each plate is 0.075m.
The hollow cylinder functions as storage chamber to hold water at a capacity of 0.19m3/m2
of pavement area. Generally, stormwater permeates the road pavement to reach storage
chambers placed underneath. Each cylinder has an inner diameter of 0.28m and a thickness of
wall of 0.06m. Height of each cylinder is 0.3m.
A pilot scale of using StormPav units as road is reported in [7]. These units are interlocked
to form a 11m x 4m low volume road in the suburb of Kuching city, Sarawak. The pilot project
demonstrates successful implementation of StormPav as multipurpose road, namely pavement
at the top layer to support passing of vehicles, stormwater detention in the middle layer
replacing the use of aggregates in the conventional road making, and lastly raft foundation at
the bottom layer that could have lessen the compaction works a conventional road should need.
Other than road, it could be adopted as road shoulder. The concept is presented in Figure
3, an enhancement to those in Figure 2. StormPav plates at the top layer could be used as
footpath. Its hollow cylinders in the middle layer could be the tool to capture road runoff when
the road-curb and stormwater inlet are merged with StormPav. Moreover, the StormPav units
could be assembled on site that allows faster construction than conventionally having concrete
mixtures cast in-situ.
3. MODELLING APPROACH
A typical road shoulder in a housing estate is taken as case study. Referring to Figure 4, the
maximum width of road shoulder is 1.5m. There is no limit to the length of the road shoulder.
However, a length of road shoulder is needed to demonstrate the usefulness of stormwater
detention being incorporated in it.
http://www.iaeme.com/IJCIET/index.asp
402
editor@iaeme.com
Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo
Figure 3 StormPav units as road shoulder
A length of 6.5m is the shortest length, usually between two residential houses. As such,
6.5m x 1.5m road shoulder is engaged as a single unit of stormwater detention for flow pattern
visualization in the next section. Such a size allows a stormwater detention capacity of 1.85m3.
Figure 4 Case study
The associated road and road shoulder contribute to a catchment size of 6.5m x 7.5m.
Running water generated from the catchment is directed to a curb-opening inlet before entering
the StormPav road shoulder. Water leaves the StormPav road shoulder via outlet connected to
the adjacent urban drain. Appropriate sizing and placement of inlet and outlet are crucial to
ensure proper functioning of the stormwater detention [10]. Too small may cause overflow and
http://www.iaeme.com/IJCIET/index.asp
403
editor@iaeme.com
Stormwater Detention in Road Shoulder using Stormpav Green Pavement System
congestion of flow, while too big may cause rapid disposal of stormwater to compromise its
detention functionality.
In this project, the component parts consist of road curb and road shoulder to form a
rectangular tank and StormPav units are arranged within the tank. As such, it forms a complex
system with multiple chambers due to the empty spaces in the cylinders and also between the
cylinders. A CFD model is needed to represent the complex system and SolidWorks is the tool
used to resemble the 3D StormPav modular units as well as the curb-opening inlet and outlet.
SolidWorks Flow Simulation that comes along with the SolidWorks 2018 package is used to
simulate flow through the StormPav system.
Three designs are explored here (see Figure 5). Standard curb opening of 300mm as the
curb opening is adopted in all the three designs at the centerline of the StormPav system. The
difference lies in the placement of outlet. Design 1 has a 10mm outlet placed in a straight line
as the curb opening. This arrangement is common in conventional drainage inlet and outlet
designs so that the stormwater could be discharged rapidly.
Because Design 1 has one inlet and one outlet setting, Designs 2 and 3 follow the same
number and size of inlet and outlet for meaningful comparison. The outlet of Design 2 is moved
to the edge of the StormPav system, about 3m from the centerline. The outlet of Design 3, on
the other hand, is put between the centerline and edge, about 1.7m from the centerline. These
outlet arrangements are made to explore the flow patterns compared to the common inlet/out
setting in Design 1.
Figure 5 Illustrations of (a) Design 1, (b) Design 2 and (c) Design 3
4. RESULTS AND DISCUSSION
Replicating the models done by [4], taking the worst-case scenario, 210 mm/hr of rainfall
intensity based on 5-minute 10-year ARI design rainfall is modelled on the about 50 m2 of road
http://www.iaeme.com/IJCIET/index.asp
404
editor@iaeme.com
Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo
and road shoulder surfaces. An amount of 0.85 m3 of runoff is calculated with a peak discharge
of 0.002 m3/s from the catchments to enter the StormPav system. The amount of runoff is lower
than the maximum capacity of the water storage when directed to StormPav system and is
expected to be fully captured.
Table 1 shows that the velocities for the inlet and outlet are maintained similar throughout
the three designs. The computed flow patterns between inlet and outlet are depicted in the
following Figures 6 to 8.
Table 1 Computed pressure and velocity at inlet and outlet of StormPav road shoulder
Design
1
2
3
Inlet
Pressure (Pa)
Velocity (m/s)
72072
0.0501
72072
0.0501
72072
0.0501
Outlet
Pressure (Pa)
Velocity (m/s)
73067
0.365
73062
0.374
73062
0.374
The followed plots are started with a plan view of the StormPav system at the top with
velocity contour across the system. Three cross sections are highlighted, and the locations are
specifically related to the position of outlet for Designs 1 to 3.
Cross-section 1A
Cross-section 1B
Cross-section 1C
Figure 6 Design 1 subjected to 5-min 10-year ARI design rainfall
http://www.iaeme.com/IJCIET/index.asp
405
editor@iaeme.com
Stormwater Detention in Road Shoulder using Stormpav Green Pavement System
Design 1 shows dense variations of velocity at the centerline line of the StormPav system,
while less velocity towards the left and right edges. Pressure is maintained the same across the
system. The flow pattern is imbalance, in which flow is found concentrated at the centerline
region.
Moving to Design 2, with the outlet being located the furthest left from the curb opening,
the computed flow pattern shows stark contrast with Design 1. Velocities are the highest at the
vicinity of the inlet and outlet. However, dense variations of velocity are found in the spaces
from the centerline to the left edge. It is obvious on the plan view; and the densities of velocity
are reflected in the plots of Cross-sections 2A to 2C. Pressure is maintained the same across
the system.
Cross-section 2A
Cross-section 2B
Cross-section 2C
Figure 7 Design 2 subjected to 5-min 10-year ARI design rainfall
Design 3 shares similar flow pattern as of Design 2, but on a lesser scale. Dense variations
of velocity are found between the inlet and outlet. However, velocity is found less than Design
2 at the left edge. Pressure is maintained the same across the system.
Velocity plots are transformed to flow trajectory plots presented in Figure 9. Generally,
Designs 2 and 3 have demonstrated a better distribution of flow within the StormPav system
than that of Design 1. Flow trajectory shows how the water passing through the tight spaces of
http://www.iaeme.com/IJCIET/index.asp
406
editor@iaeme.com
Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo
StormPav modular units. It allows the research team to decipher further the performance of
each of the design.
Cross-section 3A
Cross-section 3B
Cross-section 3C
Figure 8 Design 3 subjected to 5-min 10-year ARI design rainfall
The velocity plots show little velocity within the hollow cylinders as water flows more
outside the hollow cylinders. The flow trajectory plots give a better explanation, particularly
on Design 2. All spaces between centerline to left edge is found more fluent than the other two
designs. As such, Design 2 has the best distributed flow.
While the StormPav system is intended as temporary stormwater storage, the research team
would appreciate the distributed flow more pertaining to the nature of stormwater from roads
usually is laced with sediments. The stagnation portion at the left and right edges demonstrated
in Designs 1 and 3 could encourage sedimentation of what brought by the stormwater. In
contrary, the flow trajectory of Design 2 shows the characteristics of good mixing in all corners
half of the StormPav system. It could be of use to allow self-cleansing among the modular units
and lengthen the life cycle of StormPav system from sedimentation.
Another point worth mentioning, by adding another outlet to the right edge of Design 2,
the flow trajectory on the left could be duplicated to the right. This is possible because the
system is symmetrical.
http://www.iaeme.com/IJCIET/index.asp
407
editor@iaeme.com
Stormwater Detention in Road Shoulder using Stormpav Green Pavement System
5. CONCLUSION
Incorporating StormPav Green Pavement System as road shoulder with an added function of
stormwater detention is possible. CFD simulation of the StormPav system is found to provide
informative flow visualization. The most interesting finding through the flow visualization
technique reveals another unexpected function that by moving apart the distance between the
stormwater inlet and outlet, a more distributed flow could be achieved. The distributed flow
pattern suggests a self-cleansing ability within the StormPav system to alleviate built up of
sediments carried by stormwater from roads.
Design 2 with an inlet at the centerline and possibly two outlets at the furthest left and right
edges of the StormPav system suggests the best distributed flow that could have maintained
the above much desired characteristics for stormwater detention structure.
(a)
(b)
(c)
Figure 9 Flow Trajectories within (a) Design 1, (b) Design 2 and (c) Design 3
http://www.iaeme.com/IJCIET/index.asp
408
editor@iaeme.com
Zi Sheng Lui, Darrien Yau Seng Mah and Fang Yenn Teo
ACKNOWLEDGEMENT
The authors thank the financial support from Exploratory Research Grant Scheme
ERGS/TK03(02)/1009/2013(06), rendered by the Malaysian Ministry of Education.
REFERENCES
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
Lin, J.-Y., Chen, C.-F., Ho, C.-C. Evaluating the effectiveness of green roads for runoff
control. Journal of Sustainable Water in the Built Environment, 4(2), 2018, pp. 040180018, DOI:10.1061/JSWBAY.0000847.
McPhillips, L. E., Matsler, A. M. Temporal evolution of green stormwater infrastructure
strategies in three US cities. Front. Built Environ., 4(26), 2018, DOI:
10.3389/fbuil.2018.00026.
Blecken, G.-T., Hunt III, W. F., Mohammed Al-Rubaei, A., Viklander, M., Lord W. G.
Stormwater control measure (SCM) maintenance considerations to ensure designed
functionality. Urban Water Journal, 14(3), 2017, pp. 278-290, DOI:
10.1080/1573062X.2015.1111913
Mah, D. Y. S., Ng, T. C., Putuhena, F. J. Integrating infiltration facility to urban road
drainage. International Journal of Engineering and Technology, 7(3.18), 2018, pp. 31-35,
DOI: 10.14419/ijet.v7i3.18.16668.
Mannan, M. A., Bateni, N., Teo, D. C. L., Mah, Y. S., Putuhena, F. J., Ng, C. K., Bustami,
R. A., Ibrahim, W. H. W., Lee, C. L. F., Lim, H. L. StormPav, System and Method of Green
Pavement, Application Number PI2016704420. Kuala Lumpur: MyIPO, 2016.
Mah, D. Y. S. Potential of Road Subsurface On-Site Stormwater Detention System. Kota
Samarahan: UNIMAS Publisher, 2016, ISBN 978-967-2008-05-7.
Mah, D. Y. S., Mannan, M. A., Ibrahim, W. H. W. Pilot study of StormPav Green Pavement
System. International Journal of Research in Engineering and Advanced Technology, 6(5),
2018, pp. 29-35.
Ngu, J. O. K., Mah, D. Y. S., Bong, C. H. J. Flow characteristics of individual lot
stormwater detention. Water Practice and Technology, 11(4), 2016, pp. 721-727,
DOI:10.2166/wpt.2016.079.
Liow, C. V., Mah, D. Y. S., bin Mohd Arif Zainol, M. R. R. Modelling of stormwater
detention under urban road for conveyance and storage. International Journal of Research
in Engineering and Advanced Technology, 6(5), 2018, pp. 23-28.
Senior, M., Scheckenberger, R., Bishop, B. Modeling catchbasins and inlets in SWMM.
Journal of Water Management Modeling, 26, 2018, C435.
http://www.iaeme.com/IJCIET/index.asp
409
editor@iaeme.com