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TRANSCRIPT
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P. KNIDMAT MAKLUMAT AKADEMIK UNIMAf
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POTENTIAL OF ROAD SUBSURFACE
ON-SITE STORM WATER DETENTION SYSTEM
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POTENTIAL OF ROAD SUBSURFACE
ON-SITE STORM WATER DETENTION SYSTEM
DARRIEN MAH YAU SENG
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1i. 2.? 5201 ý
© Darrien Mah Yau Seng 2016
All rights reserved. No part of this publication may be reproduced, stored in retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publisher.
Published in Malaysia by
UNIMAS Publisher, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, Malaysia.
Printed in Malaysia by
PPKS PRODUCTION SDN. BHD (673666-")
Jalan Canna, Off Jalan Wan Aiwi
Tabuan Jaya 93050
Kuching, Sarawak, Malaysia.
Perpustakaan Negara Malaysia Cataloguing-in-Publication Data
Mah, Darrien Yau Seng, 1977- POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM / DARRIEN MAH YAU SENG Includes index Bibliography: pages 63 ISBN 976-967-2008-05-7 1. Flood control. 2. Pavements. 3. Urban runoff--Management. 1. Title 627.42
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PREFACE
This is the full report for UNIMAS Small Grant Scheme F02(S147)/1127/2014(12).
The idea of having a road subsurface detention system was first surfaced in 2012. A group of UNIMAS researchers had contributed to the methodology
of setting up such a system. It took a couple of years to see the idea grew to become an actual product. This technical report is the first, hopefully in
a series of reports on a product named StormPav. Here, the hydrological
aspects of road subsurface detention system are explored, investigated
and discussed. It presents the initial results spearheading the forming of
prototype for further studies.
The author would like to express gratitude to other team members who have been working hard for this project. It has been a delightful journey
to be able to involve in the birth of StormPav, and wishes are extended to have the product succeeded against the test of time for many years to
come.
Dr Darrien Mah
March 2016
VII
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EXECUTIVE SUMMARY
Hydrology
No. Highlight Justification Page
1 Design rainfall of 3 DID Sarawak has a categorization of hours 10-year ARI is rainfall intensity, in which > 60 mm/h adopted for worst case is classified as Very Heavy or Red Alert
scenario. storm. 39
Intensity = 59.5 mm/h Depth = 178.4 mm
Prototype Design
No. Highlight Justification Page
1 Prototype has a top cover, Conventional road paving consists of a bottom plate and a layers of aggregate and top bitumen hollow cylinder as a single furnish up to 0.4 m. The different 34 unit of OSD. Total height is is small as not to cause too drastic
0.45 m. change in road laying practices. 2 Storage layer consists of It is recommended to have full
35 0.3 m in height with multi- detention of road-generated surface 42 unit hollow cylinders of runoff, because road catchments are 52 Inner diameter = 0.28 m relatively small, only 10% compared 53 Thickness of wall = 0.06 m to house catchments.
3 Top cover layer is also the The surface open area, consists of pavement layer, which is inlet hole and gap in between units, is 0.075 m thick. calculated as: 35 Hexagonal plate = 0.1624 Surface open area / pervious = 2% 43 mZ Concrete surface / impervious = 98% 44 Inlet hole = 0.04 m Permeability rate = 180 mm/hr per 45 diameter hole Perimeter = 1.5 m
ix
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4 Bottom plate layer lays The focus is more emphasized on on native soil separated storage. As long as the capacity to 36 by a layer of geotextile. store stormwater is met, infiltration 42 Similar to top cover, every and slow release are then ensured plate has a hole of 0.04 m processes that follow. Therefore, both in diameter. Gap exists in are excluded at this stage. between units.
Study Area
No. Highlight Justification Page
1 Residential area in It is a representation of typical Lorong Keranji 4, Tabuan housing estate. 37 Jaya
2 Road width is 3m wide The road is local street classified as one way; 6m for two JKR Class U3 Urban road, with speed
37
ways. control below 60 km/h. 38
Storm Conveyance Model
No. Highlight Justification Page
1 SWMM version 5 is used. SWMM is the oldest computer 40 software for stormwater modelling.
2 MSMA is extensively MSMA is recognized as the official 69 referred. guideline for stormwater-related 70
design in Malaysia. 3 Disconnected System This model is used to demonstrate
model the distribution of surface runoffs 51
from different catchments in the 52 53
study area.
x
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4 OSD Section model This model is specific to a section of road catchment.
Area =3mx1.3 m The road width complies with ]KR 54 (1% of 1-way lane) U3. 55
The length follows the design of rainfall simulator the researcher team Intended to fabricate.
It is modelled as This modelling technique Is found to 42 "pavement with storage". be the most workable in the context 43
of Road Subsurface OSD.
Modelling Results
No. Highlight Justification Page
1 OSD Section subjected Simulation of worst case scenario to 3 hours 10-year ARI Indicates a need of road kerb at least
design rainfall 100 mm high to contain the volume of stormwater and allow them to 57
permeate to storage chambers over time. Excessive surface ponding is predicted.
2 OSD Section subjected It is a light storm but spanned for to observed January 15 10 hours continuously. Intensity of
storm event rainfall was below 10 mm throughout 58 the event. Simulation of this event 59 shows the OSD functions adequately. No surface ponding is predicted.
3 O5D Section subjected It is a heavy storm for only 4 hours, to observed January 5 with high intensity at the beginning storm event and slowly weakening over the course
of storm. Simulation of this event 58 observes full capture of the rainfalls 59 that reinstating the OSD functions
adequately. Only slight surface ponding is predicted.
XI
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Puset KhiÄmlt MAtnmivt AVa+-mft UNIVERSItI MAt. kvc. I+ cqRa u"K
Tables of Contents
Preface
Executive Summary
Table of Contents
List of Tables
List of Figures
CHAPTER 1 INTRODUCTION
1.1 Background 1.2 On-Site Detention System
1.3 Problem Statement
1.4 Hypothesis
1.5 Organization of Monograph
CHAPTER 2 LITERATURE REVIEW
2.1 Natural Hydrologic Cycle
2.2 Urban Hydrologic Cycle
2.3 Stormwater Management
2.4 Water Sensitive Urban Design
2.5 On-Site Detention
2.6 Urban Storm Water Management Manual for Malaysia
2.7 Design Criteria 2.8 Modelling of On-Site Detention 2.9 Case Studies of On-Site Detention
CHAPTER 3 METHODOLOGY
3.1 Proposed Design
3.2 Modelling Approach
3.3 Study Area
3.4 Design Rainfall
3.5 Surface Runoff
3.6 Detention Storage
3.7 Representation of On-Site Detention
vii
ix
xiii xv
xv
1
1
2
3
3
4
5
5
7
8
9
11
16
18
21
23
33
33
35
37
39
40
41
42
xiii
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CHAPTER 4 RESULTS AND DISCUSSION 51
4.1 Rationale of Modelling Approach 51
4.2 Modelling of Road Surface On-site Detention 54
CHAPTER 5 CONCLUSIONS AND RECOMMENDATION 61
5.1 Conclusions 61
5.2 Recommendation 62
REFERENCES 63
APPENDIX A Design Rainfall for Kuching 69
APPENDIX B Computation of Runoff for Disconnected System 69
APPENDIX C SWMM-Computed Runoff 70
APPENDIX D References of PSD, SSR, Inlet, Outlet and Storage 70
Volume
APPENDIX E Observed Rainfall of January 2014 71
APPENDIX F Fl. Output of OSD Section subjected to January 15 Storm Event 71
F2. Output of OSD Section subjected to January 5 Storm Event
72
INDEX 73
XIV
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LIST OF TABLES
2.1 Summary of SWMM Modelling Techniques and Measurement of Efficiency
3.1 Measurement of Study Area
3.2 Properties of JKR U3 Urban Road
3.3 Categorization of Rainfall Intensity (mm per hour) 3.4 Estimation of Surface Perviousness of OSD Section 3.5 Recommendations of Permeability for Permeable Pavement 3.6 Examples of Kerb Heights
3.7 Modelling Parameters of OSD Section 4.1 Amount of Computed Runoff 4.2 Estimation of Road Subsurface OSD Volume 4.3 Expected Outcomes for Verification of OSD Section 4.4 Output of OSD Section Modelling
LIST OF FIGURES
32
38
38
39
44
45
46
49
52
53
54
57
2.1 Hydrologic Cycle (www. exploringnature. org) 6 2.2 Scenarios of Hydrograph (Sidek et al., 2004; Zakaria et al., 2004) 10
2.3 Typical On-Site Detention Storage Facilities (DID, 2012) 12
2.4 Examples of Below-Ground Tank 13
2.5 Examples of Below-Ground Pipe Packages 14
2.6 Examples of Below-Ground Precast Concrete Block with Hollow 15 Chamber
2.7 Examples of Below-Ground Modular Block 16 2.8 Nonlinear Reservoir Representation of a Subcatchment (Huber
20 and Dickinson, 1988)
2.9 Inflow and Outflow Hydrographs for Detention Systems (PUB, 21 2010)
2.10 Conceptual of Drainage Modelling 23 2.11 Modelling of Detention Tank In Belo Horizonte (Drumond et al., 24
2013)
xv
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2.12 Modelling of Detention Tank in Czestochowa City (Mrowlec and 26 Kisiel, 2008)
2.13 Modelling of Drainage System in Meakin Terrace (Pezzanitl, 27 2006)
2.14 Modelling of Mostacciano Experimental Catchment (Rianna et al., 29 2011)
2.15 Modelling of Drainage Area A of Metro West (LID Design Group, 30 2005)
2.16 Modelling of Easy Street (Dierks, 2009) 31
3.1 Comparing Conventional Paving and Road Subsurface OSD 34
3.2 Properties of Road Subsurface OSD 35
3.3 Concept of Stormwater Conveyance Model 36
3.4 Aerial of Lorong Keranji 4 (www. bing. com/maps/) 37
3.5 Rainfall-Runoff Simulation in SWMM (Huber and Dickinson, 1988) 40
3.6 Representation of Subcatchment in SWMM for Runoff Computation 41
3.7 Storage Layer 41
3.8 Top Cover-Cum-Pavement Layer 43
3.9 Experiment to Investigate Permeability Rate 47
4.1 Subcatchmentsin Study Area 51
4.2 OSD Section in Relative to Disconnected System Model 52
4.3 Input of Data for OSD Section 56
4.4 Modelling of OSD Section 57
4.5 Detention of 10-hour Observed Light Storm 59
4.6 Detention of 4-hour Observed Heavy Storm 59
xvi
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CHAPTER 1
INTRODUCTION
1.1 Background
Removal of vegetation from land and construction of impervious surface
on it result in changes to surface runoff pattern (Goonetilleke et al., 2005),
increasing stormwater surface runoff and its peak flows (Al-Hamati et al.,
2010 and Barbosa et al., 2012). Hibbert (1967) mentioned that there is
clearly an increase in overland flow due to a reduction in forest cover; and
Hollis (1975) concluded that frequency of small floods increases many
times due to rapid urbanisation, while occurrences of large rare floods are
not significantly affected.
Increasing precipitation leads to large volumes of stormwater runoff; this
has been found to be one of the major causes of flash floods due to
decreasing rates of infiltration and ground water recharges (Liew et al.,
2012), The existing drainage systems are insufficient to carry the volume
of stormwater runoff during the precipitation periods. A conventional
approach practised in Malaysia is to allow developers to put in drains
where appropriate, but the government engineers determine the drain
sizes that will comply with the drainage capacity and final discharge outlet
1
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POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM
requirements. To maximise housing density, developers normally channel
all drainage to concrete-lined and open channel type of large trunk drains
(Zakaria et al., 2004).
The conventional drainage system in Malaysia is based on the first urban
drainage manual "Planning and Design Procedure No. 1: Urban Drainage
Design Standards and Procedure for Malaysia" which was published by the
Department of Irrigation and Drainage (DID) Malaysia in 1975. Drainage
designs based on this manual unfortunately have led to occurrences
of flash floods at the downstream of catchments, and therefore the
conventional drainage is no longer an effective measure in solving flood
problems (Zakaria et al., 2004).
In order to find more effective solutions, the above-mentioned manual was
superseded by another urban drainage manual known as Urban Storm Water
Management Manual for Malaysia (Manual Saliran Mesra Alam or MSMA). Water
Sensitive Urban Design (WSUD) has been implemented as the core of MSMA.
It is meant to control the quantity and quality of runoff through detention/
retention storages, infiltration facilities, and engineered waterways which are
capable of retarding the peak flows (Zakaria et al., 2004). The application of
MSMA, in the long term, helps to minimise the government allocation for flood
mitigation programmes. Among the many WSUD measures, On-Site Detention
(OSD) system is chosen as the focus of study in this research project.
1.2 On-Site Detention System
Stormwater detention provides flood-control benefits, by capturing
portions of urban runoff, and thus reduces the runoff volume. OSD systems
have been widely applied in Sydney since 1991; the developers provide
2
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CHAPTER 1 INTRODUCTION
detention storages for stormwater on their project sites to limit rates of
runoff (O'Loughlin et al., 1995). Examples of such systems are highlighted
in Chapter 2.
1.3 Problem Statement
it is difficult to adopt the practice of OSD when large tracts of land
are not easily available. Therefore, this study project carries out
an experiment to use road subsurface rather than open spaces
for the purpose of OSD. Attempts are made to store stormwater
under the road to achieve the function of an OSD.
The design of the OSD system is in the form of constructed chambers
as a road subsurface layer. The details of the system are discussed
in Chapter 3. It is a rather new concept and therefore not much
information is available. In the context of hydrology, the extent
of such design to intercept urban runoff and its effectiveness as
an OSD are crucial to convincingly introduce this measure to the
community. A computer model would give a convenient simulation
and generate some performance results of such design.
1.4 Hypothesis
The surface runoff on roads can be directed to multi-unit storage
chambers under the road surface. The system should be able
to detain the stormwater over a period of time. Inlets therefore
should be efficient enough for the water to permeate through
them.
3
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POTENTIAL OF ROAD SUBSURFACE, ON-SITE STORMWATER DETENTION SYSTEM
A hydrological study is always site specific, and the selected study area
is a typical residential area with low traffic roads in Kuching, Sarawak.
Simulation is carried out using EPA SWMM 5.0 software. The design of the
stormwater system is based on the guidelines as contained in the official
Malaysian manual, i. e. MSMA and SWMM.
1.5 Organisation of Monograph
The first chapter of this monograph is introduction to the study.
It consists of the general views of the topic, a problem statement
and outlined hypothesis.
The second chapter is literature review, in which important terms
and necessary information are explained in detail. This chapter
consists of the elaboration of WSUD, stormwater management,
OSD, and the modelling of the stormwater system.
The third chapter discusses the methodology and the procedures
used in order to test the hypothesis of this study. This chapter
explains the methods adopted for the research, which include
model building and assumptions made.
The fourth chapter covers results obtained from the usage of
methods adopted in Chapter 3. The results are elaborated and
evaluated in order to investigate the application of road subsurface
as OSD. The last chapter concludes the findings of this project and
presents recommendation for future studies.
4
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Pusat KhidmAt til'aleHlr»at Ak>'º(femik t. 1NIVERSITI MAI, *YStA 1, ARqWak
CHAPTER 2
LITERATURE REVIEW
2.1 Natural Hydrologic Cycle
Hydrology is the study of water and its properties, distribution, and effects
on the earth as it cycles through the earth's surface, subsurface, and
atmosphere (McCuen, 2005). Physical hydrologic processes that control
the distribution and movement of water in an area, over the surface of
the earth, and through the ground, are best understood in terms of the
hydrologic cycle.
The hydrologic cycle defines the naturally occurring processes that manage
water. It shows that the processes are interdependent, and the knowledge
of each is necessary to understand problems related to water quantity and
quality as well as their solutions. The whole cycle is ultimately driven by
solar radiation, which evaporates water from the ocean and lifts it up to
the atmosphere.
Figure 2.1 shows the processes of the hydrologic cycle system. The
complete hydrologic cycle consists of atmospheric, surface, subsurface
and interfacial processes. The atmospheric processes consist of cloud
condensation and precipitation; meanwhile, the surface processes
consist of snow accumulation, overland flow, river flow, and lake storage.
5
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POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM
Infiltration, soil-water storage and groundwater flow are classified as
subsurface processes; meanwhile, evaporation, transpiration, sediment-
water exchange are interfacial processes. In short, the components of
hydrologic cycle are surface runoff, evaporation, transpiration, infiltration,
precipitation and groundwater storage.
plants open thcir porn for carbon dioxide and lose water to evaporation (trawpMatlan)
water vapor cools and changes back into liquid
form (condsnsatlon)
water, driven by the heat of the tun, changes into vapor and rises
into the air (evaporation)
Figure 2.1: Hydrologic Cycle (www. exploringnature. org)
Precipitation is the hydrologic cycle component that initiates runoff (Davis and Cornwell, 2008). As rain falls, it ultimately reaches the ground
surface. Some stormwater is intercepted by vegetation. Some is stored
in surface depressions, with almost all of that in the depression storage
infiltrating into the ground. Water stored in depressions, water intercepted
by vegetation, and water that infiltrates into the soil during the early
part of a storm represent the initial losses where it does not appear as
6
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CHAPTER 2 LITERATURE REVIEW
runoff during or immediately following a rainfall event. Once the ground is
saturated, stormwater starts to flow.
This overland flow is known as surface runoff. It flows on the ground
surface into ponds, lakes, streams or oceans and water from these bodies
are again evaporated back into the atmosphere. Water entering an upland
stream travels to increasingly larger rivers and then to the seas and
oceans. Infiltration occurs when water seeps into the ground and trapped
between rocks and soils as groundwater. The amount of water stored in
the soils determines, in part, the amount of rain that infiltrates during the
next storm event. Some of the water stored in the soil near the plants is
taken up by the roots of the vegetation, and subsequently transpires back
to the atmosphere from the leaves of the plants.
2.2 Urban Hydrologic Cycle
The natural hydrologic cycle is interrupted by rapid developments in urban
areas. As the population of the world Increases, changes to the land have
often been significant, with major alteration to the runoff characteristics
of watersheds. The biggest problem associated with urbanisation is the
increase in impervious surfaces. As defined by Chabaeva et at. (2009),
impervious surfaces are "artificial features, such as concrete surfaces,
pavements, and building rooftops that replace naturally pervious soils and
prevent precipitation from infiltrating the soil. " Spencer et at. (2009) and
Savary et al. (2009) agreed that land use change and impervious surfaces
have significant impacts on the hydrologic processes within a watershed
such as evapotranspiration and surface runoff. Urban watersheds are dominated by concentrated areas of human activities and are primarily
composed of impervious surfaces which partially eliminate the natural
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POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM
processes that manage stormwater. This results in increased runoff
volumes and peak flows (Burns et al., 2005).
Over the last two centuries, urbanisation has caused significant changes to the landscape surrounding these urban centres (Sauer et al., 1981).
Continued growth results in increased capitalisation of the existing urban
areas and redevelopment to higher density housing. Some of these
activities are likely to be in flood-prone areas. For intense storm events,
where runoff exceeds the capacity of the local drainage system, flash flood
occurs.
2.3 Stormwater Management
Stormwater management is the mechanism for controlling stormwater
runoff. Best Management Practices (BMPs) are documented worldwide to
assist authorities for the mentioned purposes. Different approaches can be
followed to deal with stormwater: strategic decisions, political decisions,
source control or "end of pipe measures" (German et al., 2005).
In countries like the United States of America, the United Kingdom and
Australia, stormwater management is applied not only to the overall
stormwater management facilities (for example, regional ponds and
wetlands), but to individual homes through BMPs. Their holistic approaches
towards stormwater management have resulted not only in the reduction
of flash floods, but also improved environments through replenishment of
groundwater tables.
BMPs are design techniques used to achieve the desired post-development hydrologic conditions. BMPs deal with stormwater by taking into account
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CHAPTER 2 LITERATURE REVIEW
both future needs and the protection of natural resources (Hvitved-
Jacobsen et al., 2010). Non-structural BMPs are practices designed to limit
the generation of stormwater runoff or reduce the amounts of pollutants
contained in the runoff. They minimise the total disturbed area, soil
compaction and cluster development. On the other hand, structural BMPs
are engineered and constructed systems that improve the quality and
control the quantity of stormwater. These include bio-retention facilities,
detention basins, vegetated systems, infiltration trenches, pervious
pavements and rainwater harvesting (Martin et al., 2007).
2.4 Water Sensitive Urban Design
WSUD introduces a range of measures that are designed to minimise the
impacts of urbanisation. According to Melbourne Water (2002), WSUD
marks a shift in thinking towards stormwater management where all water
streams are considered as a resource. All city sites, including buildings,
roads, footpaths and open spaces can contribute to sustainable water
resources management across the municipality.
The concept of WSUD is to reduce the volume and speed of stormwater
runoff in drainage systems. Other than that, WSUD also serves to protect
natural waterways within urban development, to Integrate stormwater
treatment into the landscape, to protect the water quality of receiving
waterways and bays by removing pollution close to their sources, to
manage the stormwater locally as it flows from upstream in order to
reduce the need for bigger drainage infrastructure downstream and to
reduce the overall cost of drainage infrastructure.
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POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM
In an attempt to compensate for the loss of natural storage, many
localities require the replacement of the lost natural storage with man-
made storage. Detention basins are one of the WSUD measures. It is
a stormwater structure that provides temporary storage of stormwater
runoff. Its primary purpose is to attenuate stormwater flow, which leads
to reduction of peak runoff rates.
They are separated into on-site and regional detention (DID, 2012).
The design of stormwater detention basins requires the knowledge of
water routing through the hydraulic outlet structure and the knowledge
about surface runoff into the detention basin. In some detention basins,
infiltration process is incorporated (Gribbin, 2001). The importance of
storing stormwater runoff in large basins has been well recognised (Dunne
and Leopold, 1978; Whipple, 1979).
Figure 2.2 shows the requirement that the quantity of surface runoff from
developing area should be maintained to near pre-development condition.
Post Development Uncontrolled Runoff
----- Pre-Development Uncontrolled Runoff
Post-Development Controlled Runoff by Detention
Time
Figure 2.2: Scenarios of Hydrograph (Sidek et al.; Zakaria et al., 2004)
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CHAPTER 2 LITERATURE REVIEW
Peak runoff can be reduced through the implementation of BMPs:
detention tanks, retention ponds or sedimentation basins, wetlands, green
roofs, bio-retention swales, porous pavements, etc. Reduction in peak
runoff can be achieved by using one or a combination of the mentioned
measures, depending on the availability of space, intended functions of
the stormwater management system, and costs.
2.5 On-Site Detention
Storage facilities are the core elements of achieving one of the major
stormwater quantity control criteria - the post-development peak discharge cannot be more than the pre-development peak discharge.
An OSD system provides storages for stormwater to compensate for the
increased runoff from the development. It was first introduced and widely
used in Australia as a means of controlling the increased storm discharges
from urban consolidation projects (O'Loughlin et al.; Phillips, 1995). With
proper placing and sizing of the storage facilities (Guo, 1999), these
systems are considered the major type of stormwater control system in
urban areas (ASCE, 1992).
Detention storages collect and store stormwater runoff during a storm
event, then release it at controlled rates to the downstream drainage
system, thereby attenuating peak discharge rates from the site. With such
a system in place, the drainage system as a whole can cater for higher
intensity storms brought about by increasing uncertainties due to climate
change.
OSD identifies an entire plethora of storage facilities which are present in
the upper reaches of the flow conveyance system. The primary difference
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POTENTIAL OF ROAD SUBSURFACE ON-SITE STORMWATER DETENTION SYSTEM
of OSD with local disposal and inlet control facilities is in the amount of
tributary area being intercepted. OSD generally intercepts runoff from
several pieces of real estates or from an entire subdivision. This means
the water has been conveyed at least a short distance before it arrives at
the detention facility.
Figure 2.3 shows the typical OSD facilities. OSD can be provided above
ground, below ground, or a combination of both (DID, 2012). The above-
ground storages (basically as tanks) can be located on rooftops, lawns,
gardens, car parks, driveways, etc. It is easy to construct and cheaper
than below-ground storage as it does not require much piping system.
Rooftop
,- Landscaped Area 0000 ' 000o , ý-ý�ýý
Underground Tank Pipe Package --
I
Figure 2.3; Typical On-Site Detention Storage Facilities (DID, 2012)
On the other hand, the below-ground storages consist of tanks and pipe
packages. The author would like to add two more types, namely chamber
and modular blocks. These storages are used in developed areas where
land cost and/or availability are of major concerns (Al-Hamati et al., 2010).
The concept of OSD system also can be similar to wetland's function that
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