1.
Introduction
1.1 Background Information
This proposal has been
developed in response to the request for proposals for developing solutions for
an engineering problem.
As Singapore becomes
more urbanised, there will be an exponential increase in surface runoff. This
is due to porous ground surfaces being replaced by non-porous infrastructures.
According to Public Utilities Board (PUB) (2018), Singapore currently has an
estimated 8,000 km of drains, rivers and canals. However, as global warming
persists, climate change will bring about a more drastic and erratic weather,
with expectancy of persistent and intensified storms. There is a certain limit
to the expansion of drains, hence, Singapore has to implement additional
measures to better manage stormwater.
A
survey was conducted to evaluate potential need for solutions. It is clear from
the results that more than 90% of students felt the need for the new SIT
Punggol campus to adopt effective and integrated stormwater management
approach, with environmental and aesthetic considerations to prevent flooding
and ponding issues in the new campus.
The new SIT Punggol
campus is an environmentally-friendly campus with state-of-the-art facilities.
An integrated stormwater management approach such as ABC Waters, which is
regarded as an outstanding stormwater management practice is not planned as yet
for the new campus. Furthermore, the new campus is located in a highly
urbanised environment in which many developments such as roads and roofs are
mostly made up of impermeable surfaces. This increases stormwater runoff and
further increases flooding and ponding risks in the campus.
It
is clear that flood and ponding can bring about severe inconvenience and pose
serious safety hazards to the university community as well as the public.
Ponding can also encourage the breedingof unwanted pests if it remains stagnant
for too long. Without plans for an integrated approach in stormwater management
for the new campus, the mentioned impacts can happen and negatively affect
members of the university community and the public. The modern and new campus
is known by the industry to be smart and green, adopting traditional stormwater
management methods would not reflect well on the campus. Therefore, there is a
need for the new campus to adopt the ABC Waters design approach.
Adopting the ABC Waters design
approach in the new campus realises the ideal campus which the team has in mind, which is a
forward-looking SIT campus at Punggol with an integrated stormwater management
approach known as ABC Waters, which is environmentally-friendly, aesthetically
pleasing, and of educational value to members of the university community and
the public.
1.2 Problem Statement
An ideal forward-looking
campus should adopt an integrated approach which encompasses environmental and
aesthetic aspects for stormwater management. However, such an approach in the
new SIT Punggol campus is not planned as yet. By adopting ABC Waters design
approach into the new campus, flood and ponding risks are reduced, stormwater
management at the campus would be environmentally-friendly, aesthetically
pleasing, and of educational value to members of the university community and
the public.
1.3 Purpose Statement
The purpose of this
report is to propose to the planning committee of SIT Punggol campus to adopt
the ABC Waters design approach for stormwater management into the new campus,
and to highlight to the committee that this design approach is
environmentally-responsible, reduces flood and ponding risk, enhances the
aesthetics of the campus and at the same time serves an educational purpose.
2.
Proposed Solution
The
team’s proposed solution to alleviate flooding and ponding occurrences in the
new SIT Punggol campus, is to incorporate ABC Waters management strategy into
the campus, specifically at areas where drainage networks are prominent. ABC
Waters management strategy is a holistic stormwater management system which
relies on the usage of natural features to improve surrounding aesthetics,
surface water quality and reduce flooding (PUB, 2014). The team would like to
propose two ABC Waters natural design features, namely vegetated swales and
bioretention swales into the proposed ABC Waters management strategy for the
new campus.
2.1 Vegetated Swales
Vegetated swales are
natural drainage channels with a mild slope that help to remove soil particles
and transport water through overland flow. Vegetated swales prevent damage to
waterways caused by “erosive flows” resulting from often occurring “storm
events” (PUB, 2014). Vegetated swales have a slower flow velocity in comparison
to concrete-lined drains, hence vegetated swales are able to prevent damage to
waterways.
2.1.1 Application
Vegetated swales can be
strategically placed around the campus, mainly above compound drains. It is
necessary for vegetated swales to be constructed such that the channel flows
from higher to lower ground elevation. According to North Carolina’s Department
of Agriculture and Consumer Services (n.d.), the first stage in designing a vegetated
swale is to consider the site limitations.
The shape, width and
slope of the vegetated swale must be carefully designed in regards to the
blueprint of the SIT@Punggol campus. Triangular swales are advisable for areas
with smaller drainage areas as the flow depth allows for the vegetation and
soil to have an increased contact with the stormwater, which in turns increase
infiltration and filtration.
The following listed
points are the maintenance considerations of vegetation swales:
i. - Scheduled assessment of overflow and inlet
areas to ensure clear obstructions
ii. - Scheduled assessment of waste, debris and
other foreign materials
iii. - Scheduled assessment and mending of
vegetated swale report
iv. - Well maintenance of vegetation growth
v. - Extraction and weed control
vi. - Irrigation of vegetation during dry
periods
2.2 Bioretention Swales
“Bioretention swales are
also vegetated swales with bioretention systems located within the base.” (PUB,
2014). Bioretention swales produce efficient treatment of stormwater runoff and
are constructed to have a gentle gradient and temporary ponding, to expedite
infiltration. They can be used in various areas such as roads, car parks and
residential areas. Rain gardens are a type of bioretention swale. Hu and Guo
(2014) explained that stormwater that flows through rain gardens are detained
shortly and cleansed through soil filtration before it flows to the nearby
water bodies.
2.2.1 Application
Bioretention swales can
be implemented in the new campus and designed such that longitudinal slope is
achieved. Slope that is too steep would cause flows to be erosive while a mild
slope would cause water stagnation that can lead to mosquito breeding. Figures
2 and 3 illustrate the components of bioretention swales.
With reference to
Townsville City Council (n.d.), establishing bioretention swales include
“Bulking out and trimming”, erecting of “outlet structures”, arrangements of
liner and establishing under-drains and drainage layers, installation of a
filtration media before adding a surface of 25mm topsoil, turf then geofabric
as a temporary protective layer . The temporary layer will act as an protection
system for the bioretention system when it is undergoing its subdivision and
construction phases. The protection layer will prevent any foreign substances
such as litter, sediments and laden waters from infiltrating and clogging the
filter media.
Various vegetation types
such as sedges and tufted grass can be used for bioretention swales in the
campus. PUB (2014) stated that dense vegetation that are planted along swale
components are able to reduce flow
velocities through increased sedimentation retention. Bioretention swales with
dense vegetation require minimal maintenance and at the same time able to aid
in the maintenance of soil porosity.
3.
Benefits of Proposed Solution
3.1 Reduce flood and ponding risks
The incorporation of ABC
Waters management strategy in SIT Punggol campus, along with the proposed
implementations of vegetated swales and bioretention swales greatly reduce
risks of flooding and ponding in the campus. Vegetated swales reduce the risks
by transporting stormwater runoff to neighbouring waterways and river.
Bioretention swales enable infiltration of stormwater, thus removes ponding and
minimise flooding.
3.2 Enhance surrounding aesthetics
The use of
vegetated swales can replace concrete drains which are less aesthetically
pleasing which greatly enhances the aesthetics of the campus’s surrounding
landscape.
3.3 Environmental impact
Vegetated swales purify
stormwater runoff by removing soil particles before the runoff enters the
neighbouring waterways and rivers. The purification therefore, minimises water
pollution. Similarly, bioretention swales cleans the runoff by soil filtration
before the runoff enters the neighbouring waterways.
3.4 Educational value
The proposal
of implementing ABC Waters design features in the new campus presented an
opportunity to educate members of the university community and the public on
environmental sustainability and the interesting functions of the features. The
proposal encourages public education through conduct of activities such as
eco-learning trails to raise the community’s awareness on the benefits and
functions of the green features implemented in the campus
4.
Evaluation
In this section, the
feasibility and challenges of the proposed solution will be evaluated and
discussed.
The proposed solution of
implementing vegetated and bioretention swales that purify stormwater runoff
and eventually flows towards neighbouring waterway and river is doable as the
new campus is strategically located close towards Punggol Waterway and Sungei
Serangoon. The map of the new campus and its surrounding areas is given in Apendix
1.
The existence of the
mentioned waterway and river presented an opportunity to adopt the ABC Waters
design approach of integrating drains holistically with the environment. The
proposed ABC Waters design features for the new campus have been successfully
implemented in parks and buildings nation-wide, which proved to be feasible and
successful.
4.1 Case Study: Bishan Park
According to PUB (2014),
vegetated swales were employed to replace concrete drains which purify
stormwater runoff and transport the runoff into the river.
4.2 Challenges
In order to address
doubts on the effectiveness of the proposed solution, two main challenges of
the proposed solution will be addressed. The two main challenges are mosquito
control and maintenance.
Water stagnation can
occur when water is unable to flow through soil naturally due to high clay
content and when water gets trapped in plants. These examples of water
stagnation promote favourable conditions for mosquitoes to breed. To overcome
this challenge, measures such as implementing bioretention swales can provide
infiltration of water and avoid having plants with big leaf axils (PUB, 2014)
can prevent accumulation of trapped stagnant water.
The challenges of
maintenance include ensuring sufficient and fine growth of vegetation without
using fertilisers, periodic cleaning, and inspection of the water features. To
overcome these challenges, weed removal and replanting must be performed to aid
in promoting healthy growth of vegetation. Set periodic maintenance schedule
and adhere to the schedule, ensures that the water features function as
designed for.
5.
Methodology and Procedure
5.1 Primary research
Primary research in the
form of an online survey questionnaire was conducted and the objectives are to
find out more about the thoughts of survey participants on the new SIT campus
at Punggol and evaluate the potential need for a solution. The results from the
survey were used by the team to support the team’s proposed solution. The
questions and results of the survey are given in Appendix 2.
Current SIT students were
chosen as participants for the online survey questionnaire for the following
reasons: the current students are stakeholders that would largely be affected
by the problem of flooding and ponding in the campus, and the proposed solution
will change the campus environment.
Amongst the 68
respondents, 98.5% sees a need to reduce ponding issues in the new Punggol
campus and 95.6% of them believe that there is a need for effective and
integrated approach to manage stormwater. Despite the extremely high percentages,
only a mere 20.6% of the respondents are aware of the ABC Waters concept. The
results highlight the need to raise the university community’s awareness on the
ABC Waters concept and its benefits.
5.2 Secondary research
The main source of secondary
research is from (PUB, 2014). This publication is credible and documented
comprehensive information on the ABC Waters concept, planning, design and
safety considerations, and case studies of projects that adopted the ABC Waters
design approach. Other sources of secondary research include websites which
supported the content in this technical report: (Hu & Guo, 2014),
Irrigation Outlet (n.d.) and Townsville City Council (n.d.). As for figures,
they are sourced from Lee (2013), Gougen (2014) and URA ST Graphics (2015).
6.
Conclusion
In
conclusion, the benefits of implementing ABC Waters concept into the new
SIT@Punggol campus outweigh the challenges faced. As statistics show, almost
all surveyed students would want their campus to be free of ponding with the
use of efficient, environmentally friendly and aesthetically pleasing
approaches to manage the stormwater runoff.
