The role of SuDS at the city-scale
LITERATURE REVIEW
1. LITERATURE REVIEW
1.1. Approaches to storm water management
Traditional approaches to the management of urban storm water aim at both maintaining
public hygiene and protecting urban dwellings from local flooding. Such approaches have
thus focused on the rapid removal of storm waters away from urban areas using rather
standardised methods (e.g. the rational method) and designs (i.e. end-of-pipe techniques) with
little consideration for downstream secondary effects (Chocat et al. 2001), whether this is
done by carrying storm water flows mixed with domestic wastewater in the same pipe
(combined sewers) or separately (separate sewers). As a consequence, the management of
storm waters has been dominated by rather reactive practices, systematically increasing the
capacity of combined or separate sewers as urbanisation processes and local flooding occurs,
therefore contributing to the increase of storm water peak flows and flood risk downstream
(Marsalek et al. 2006).
This relatively fixed approach was somehow reappraised in the EU since issues regarding
water pollution control and environmental protection increasingly gained importance in
research (Lijklema et al. 1993) and were subsequently incorporated into national and
communitarian legislation (e.g. Water Framework Directive). The reassessment of traditional
urban drainage designs under this new paradigm highlighted the inefficient performance of
such systems in achieving public hygiene, pluvial flooding and environmental protection
altogether (Chocat et al. 2001; Henze et al. 1997). Indeed, common problems affecting these
three key objectives still remain in most urban drainage systems as related to storm water
management, namely (Chocat et al. 2004):

Quantity problems: increase of storm water generation as urbanisation and impervious
areas expand; thereby increasing storm water peak flows and downstream flooding;

Quality problems: direct quality impacts due to diffuse pollution (e.g. heavy metals
and nutrients), CSO spills and discharge of untreated separate sewer flows into
watercourses; indirect quality impacts due to impairment of potential beneficial uses
of receiving waters (e.g. water supply, recreation, bathing, fishing, amenity, etc.);

Ecological/environmental problems: derived from quantity and quality impacts (e.g.
long-term chronic degradation of watercourses due to diffuse pollution, acute
pollution and fish kill from CSO spills, damage to habitats caused by channel erosion
during high flow storm water discharges, etc.); and

Operational problems of the drainage system and wastewater treatment plant: for
example, impaired performance of wastewater treatment works due to rapid variations
of storm flows and pollutant concentrations (e.g. deterioration of primary clarifier
performance).
In addition to this, emerging issues such as the introduction of new chemicals with an
uncertain effect on water environments, the impacts of contaminants accumulated on river
beds and drainage systems, the challenges arising from the effects of climate change or the
lower performance of an ageing drainage infrastructure are factors which may further
compromise the performance of drainage systems in the future (Chocat et al. 2004).
In response to this situation, a variety of approaches incorporating storm water quality and
environmental concerns were proposed, namely: minimising the inflow of storm water into
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LITERATURE REVIEW
sewers, growing participation of storm water utilities, and a move towards adaptive water
management… (ref?, Chocat 2001, Urban drainage redefined?).
Technical solutions which reflect concern for the aforementioned problems were then
proposed, generally in the form of ‘sustainable drainage’ or ‘best management’ practices
(more details about the planning of SuDS will be given in the next section). Although these
solutions have been commonly named using adjectives such as ‘best’, ‘low impact’,
‘sustainable’, ‘sensitive’ or ‘alternative’ (as in BMPs, LID, SuDS, WSUD and AT,
respectively), their actual effectiveness in achieving anything similar to what they pledge is
largely unknown (ref). The main reason for this is the fact that attributes like ‘sustainability’
are subjective per se.
The consideration of numerous objectives for good urban drainage practice (i.e. as related to
water quantity and quality) has been therefore expanded due to the introduction of the
sustainability agenda as a cornerstone for optimal performance (i.e. environmental protection,
social inclusion and economic well-being) (Butler et al. 2003). Sustainable water
management and, more in particular, sustainable urban drainage has become the ‘golden rule’
to propose new approaches to storm water management problems ever since.
The disparity and incommensurability of many of the objectives involved in sustainable
urban storm water management decision-making and their existing interrelationships
requires the adoption of complex multi-objective approaches (Wong & Eadie 2000; Balkema
et al. 2002). In this sense, collaborative projects such as SWARD elaborated decision-support
guidance incorporating technical, environmental, social and economic criteria that embrace
all the relevant sustainability issues within water service provision systems (Ashley et al.
2004). However, even when appropriate criteria and indicators are selected in order to assess
the sustainability of urban drainage options, ‘different individuals do not necessarily share the
same standpoint on sustainability’ (Ashley et al. 2008). Due the subjective and elusive nature
of the concept, sustainability is in fact an ‘unattainable goal’, being thus more sensible to aim
at ‘less unsustainable’ solutions when comparing drainage options (Butler & Parkinson
1997).
Certainly, as perceptions on sustainability change this should therefore be ‘a process of
learning and communication’ which is ‘constantly reviewed and adapted in light of new
information and knowledge’ (Butler & Davies 2011). Indeed, such process is particularly
important in SWM since its effects ‘extend beyond just the stormwater issues’ (sic) and new
approaches should similarly ‘move beyond just remedial technologies by combining
technology, environmental policies and public participation’ (Marsalek & Chocat 2002).
Nevertheless, the challenge in achieving ‘more sustainable’ solutions for storm water
management does not just lie on the variety of criteria to be assessed and accounted for but
also on phenomena controlling water quality or social processes, which complexity go
beyond more deterministic problems like those associated with water quantity control
(Chocat et al. 2004).
The pursuit of more sustainable (or ‘less unsustainable’) urban drainage has been, to some
extent, transformed in a debate of scale (Butler & Davies 2011). It has been argued that as
urban population rises (particularly in developing countries), and more sanitation systems are
thus increasingly required, the inability to finance traditional centralised urban drainage based
on end-of-pipe infrastructure will favour more decentralised solutions, which in turn are
deemed to be more sustainable (Ho 2003).
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LITERATURE REVIEW
Krebs & Larsen (1997) found source control measures (storm water infiltration, storm water
use, reduce water consumption, reduce pollution load to system, sewage retention tank) more
sustainable than ‘hardware’ (extend or improve the construction of the system) and ‘software’
(making better use of the current infrastructure) measures, as they reduce the complexity and
resource use intensity of the system as a whole. Also, measures aimed to improve the
resilience of receiving waters were considered beneficial from a sustainability viewpoint (see
graph from paper). Similarly, options to improve the sustainability of sanitary waste disposal
through WCs were assessed and ranked using SWARD criteria and found storm water source
control, public information campaigns and sewer rehabilitation as preferred options (Butler et
al. 2003). In this sense, Butler & Parkinson (1997) suggest three main strategies to mitigate
unsustainable drainage practice that advocate decentralised source control solutions, namely:



Reduce the reliance on water as transport medium for waste;
Avoid mixing industrial wastes with domestic sewage; and
Separate storm runoff from flows of polluted wastewater.
A summary of arguments typically used when debating the sustainability of centralised and
decentralised solutions in urban drainage systems are presented in Table 1.1.
Table 1.1: Common arguments in support (pros) and against (cons) centralised and
decentralised solutions in urban drainage systems, adapted from (Butler & Parkinson 1997;
Ho 2003; Chocat et al. 2004; Harremoes 1997).
Pros
Cons
Centralised system
Decentralised system
Proven effective and reliable technology to
hygienically remove and dispose of domestic wastes
and storm water flows.
Easier to monitor and maintain.
Suit inner centres of urban areas where space is at a
premium.
Parallel debate to transport systems, where
centralised public systems are considered less
resource consuming.
Communities select systems that suit the local
social, economic and environmental conditions.
Facilitates the integration of water, wastewater,
stormwater and water reuse at the local level.
Allows bottom-up decisions to be made at local
community level (increases public awareness).
Indirect improved efficiency on wastewater
treatment facilities.
Potential to reduce water use.
Perceived as low-tech, low-energy solutions. ‘Small
is beautiful’ views.
More severe consequences of failure (as related to
CSO spills, flooding, etc.)
Increasingly complex and expensive operation and
control of drainage systems.
More complex top-down decision-making process.
Promotes out-of-sight-out-of-mind behaviours (i.e.
low public awareness).
Decentralised
responsibilities.
Lack
of
manageability and control and maintenance. (also
Ho 2003 and Chocat et al. 2004 Burn et al. 2012)
which may lead to health hazards.
Loss of economies of scale, though individually may
be cheaper than centralised systems.
Potential for extensive uncontrolled diffuse pollution
events (e.g. groundwater contamination).
Unclear cost-effectiveness in the long term.
Increase space requirements.
‘Ecologically complicated’ and difficult to operate,
so maybe not reliable.
As adapted from (Butler and Parkinson 1997) (Ho 2003) (Chocat et al. 2004) (Harremoes 1997) (Henze 1997) (Rauch et al.
2005) (Burn et al. 2012)
The main issue here is to see whether centralised or decentralised systems fit more or less in
our ‘vision’ on sustainability. As previously explained, this view may be very different
among differing individuals and perceptions might change in light of new information and
knowledge. Thereby, solutions which are adaptable in view of long-term scenarios can be
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LITERATURE REVIEW
considered less unsustainable (Larsen & Gujer 1997). Indeed, ‘the more we invest in
extending a given system (money or resources), the more we are stuck with its specific
features and the more we tend to ‘use up’ the existing infrastructure’ (Krebs & Larsen 1997).
As a consequence of these it can be argued that traditional approaches to centralised systems
are unsustainable. However, and more importantly, even when our views on centralised
systems change, our perceptions (whether these are positive or negative) regarding the
sustainability of alternative approaches might remain stagnant. A clear example can be found
in decentralised systems, which are generally perceived as ‘harmless’, ‘low impact’ or
‘sustainable’ when the reality is that, regardless personal intuitions, ‘their impacts upon the
environment, the economy and the society are not yet fully understood’ (Chocat et al. 2004).
In fact, many concerns have been raised toward the large-scale implementation of
decentralised systems (see Table 1.1). Most of these relate to the long-term performance
(operation and maintenance) of decentralised systems and, as explained above, question to
some extent the preconceived sustainability of such practices until more information and
research outcomes becomes available.
Indeed, recent innovative drainage practice has mainly focused on environmental needs
aiming at the mitigation of urbanisation impacts (e.g. attenuation of increased flows,
sediment exports, and chemical and bacteria fluxes), whereas ‘little is known about the
economic and social aspects’ of such interventions (e.g. SuDS) (Marsalek & Chocat 2002).
This is particularly important as less unsustainable practice usually requires a ‘move from
technical fixes to non-structural solutions (or a combination of both)’ centred around social,
economic and policy spheres (Vlachos & Braga 2001).
In order to fully understand the consequences of urban drainage decisions (whether they are
centralised, decentralised or a combination of both) from a sustainability point of view,
Integrated Urban Stormwater Management (IUSM) approaches, within which cause-effect
relationships (e.g. like those involving storm water management and impacts on the receiving
waters) in the whole system are taken into account, are needed (Rauch et al. 2005). Indeed,
the consideration of individual components of the urban drainage system (i.e. sewage
network, wastewater treatment plant and receiving water) and their particular performance in
isolation has ignored the existing interrelations and interactions between these elements and
consequently missed opportunities for improvement and better understanding of the system
as a whole (Schutze et al. 2002; Muschalla et al. 2008). As it will be explained within the
next sections, modelling developments have already benefited from integrated approaches
and realised important causality relationships in drainage systems.
Now, decentralised systems and integrated approaches… (Burn et al. 2012)
Transitioning… and interaction of decentralised stormwater systems with centralised
drainage system. … (Burn et al. 2012)
More research and attention is needed in decentralised systems rather than just focusing on
centralised systems that don’t allow for reuse (Matsui et al. 2001).
Perhaps introduce with (Lijklema et al. 1993) integrated approach.
Issues at institutional level (Brown 2005)
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LITERATURE REVIEW
This paragraph introduces the integrated approaches to SWM/ also ‘from emission-based
approaches (early-current approaches in water quality control based on concentration of
emissions and quantity) to immission-based approaches (recent developments, based on
environmental status of receiving waters/carrying capacity of receiving waters’).
Appropriate institutional structures (legislation, political systems that allow for a fair and
transparent decision-making process, trustworthy institutions, key stakeholders who are in
favour of improvements and change) are essential for the implementation of sustainability
criteria (Malmqvist et al. 2006).
Achieving these objectives altogether is constrained by traditional ‘narrow’ approaches
to stormwater drainage which have been reassessed… Alternative approaches, such as
integrated
stormwater
management
(ISWM)
and…,
that
span
the
aspects/disciplines/areas involved in stormwater management aim at facilitating the
inclusion of widely diverse objectives
‘In fact, while the design of individual measures is well covered in the literature, the difficult
part is to select the best combination of measures, which would meet the project objectives’
(Marsalek & Chocat 2002).
According to the Water Environment Research Foundation (WERF 2011), the pursuit of next
generation integrated water, sustainable systems must be characterised by solutions which
would: 1) integrate wastewater, stormwater, drinking water, and other water resources; 2)
maximize energy, materials and water recovery; 3) be safe and resilient to external impacts;
4) protect water quality for designated uses; 5) maximize triple-bottom line benefits; 6)
leverage existing and emerging models for service delivery; and 7) incorporate integrated and
comprehensive water planning and smart growth planning at the national, regional and
watershed/local level.
WFD (combines emission-based and water-quality-based approaches) (see Rauch et al. 2005)
Criteria taken into account for the evaluation of drainage systems (and tools involved), see
below.
Evaluation of system performance (flooding, water quality indicators, ecology,
energy/carbon, costs, diffuse pollution, amenity). Move from environmentally-based
criteria to multi-criteria, incorporating economic/social criteria.
1.2. Planning (and assessing) more sustainable urban drainage
SuDS planning strategies.
SuDS simulation.
Optimal selection and placement of SuDS.
Assessment and impacts of SUDS in the urban environment (work to date in terms of energy,
costs, environmental impacts, diffuse pollution, and everything that matters to the project).
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LITERATURE REVIEW
1.3. Modelling the integrated urban drainage system
Approaches to the development of integrated models of urban water systems, comprising
potable and sewer networks, land surface runoff and river waters for water quality control
were proposed as early as the late 1970s (Beck 1976); however, such approaches were largely
constrained by technological limitations (i.e. computer model capabilities), and it was not
until the early 1990s that
Lijklema 1993 (INTERURBA)
Hydroinformatics references? (Abbot)
Review of integrated models (WEST, SIMBA, ICM?, Open-MI, etc.)
Review of applications (sewer system performance, WWTP, river water quality assessment,
RTC, optimisation of drainage objectives, etc.)
Issues and limitations.
Multi-objective optimisation techniques (not need for another section) in integrated model
examples…
In urban water/wastewater systems.
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LIST OF REFERENCES
2. LIST OF REFERENCES
Ashley, R. et al., 2008. Making asset investment decisions for wastewater systems that
include sustainability. Journal of Environmental Engineering, 134(3), pp.200-209.
Ashley, R. et al., 2004. Sustainable Water services: A procedural guide, IWA Publishing.
Balkema, A.J. et al., 2002. Indicators for the sustainability assessment of wastewater
treatment systems. Urban Water, 4, pp.153-161.
Beck, M.B., 1976. Dynamic modelling and control applications in water quality maintenance.
Water Research, 10, pp.575-595.
Brown, R., 2005. Impediments to integrated urban stormwater management: the need for
institutional reform. Environmental management, 36(3), pp.455-68. Available at:
http://www.ncbi.nlm.nih.gov/pubmed/16132444 [Accessed March 28, 2012].
Butler, D. et al., 2003. SWARD: decision support processes for the UK water industry.
Management of Environmental Quality: An International Journal, 14(4), pp.444-459.
Butler, D. & Davies, J.W., 2011. Urban Drainage 3rd ed., London: Spon Text.
Butler, D. & Parkinson, J., 1997. Towards sustainable urban drainage. Water Science and
Technology, 35(9), pp.53-63.
Chocat, B. et al., 2004. Urban Drainage - Out-of-sight-out-of-mind ? Position paper of the
IAHR/IWA Joint Commitee on Urban Drainage, NOVATECH 2004, GRAIE, pp.16591690.
Chocat, B. et al., 2001. Urban drainage redefined: from stormwater removal to integrated
management. Water Science and Technology, 43(5), pp.61-8.
Harremoes, P., 1997. Integrated water and waste management. Water Science and
Technology, 35(9), pp.11-20.
Henze, M. et al., 1997. Sustainable Sanitation. Water Science and Technology, 35(9).
Ho, G., 2003. Small water and wastewater systems: pathways to sustainable development?
Water Science and Technology, 48(11-12), pp.7-14.
Krebs, P. & Larsen, T.A., 1997. Guiding the development of urban drainage systems by
sustainability criteria. Water Science and Technology, 35(9), pp.89-98.
Larsen, T.A. & Gujer, W., 1997. The concept of sustainable urban water management. Water
Science and Technology, 35(9), pp.3-10.
Lijklema, L., Tyson, J.M. & Le Souef, A., 1993. Proceedings of INTERURBA ’92, the
IAWPRC workshop on Interactions between sewers, treatment plants and receiving
waters on urban areas. Water Science and Technology, 27(12).
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LIST OF REFERENCES
Malmqvist, P.-A. et al., 2006. Strategic Planning of Sustainable Urban Water Management
P.-A. Malmqvist et al., eds., IWA Publishing.
Marsalek, J. et al., 2006. Urban water cycle processes and interactions, Paris: International
Hydrological Programme (IHP) of the United Nations Educational, Scientific and
Cultural Organisation (UNESCO).
Marsalek, J. & Chocat, B., 2002. International report: Stormwater management. Water
Science and Technology, 46(6-7), pp.1-17.
Matsui, S. et al., 2001. Emerging paradigms in water supply and sanitation. In C.
Maksimovic & J. A. Tejada-Guibert, eds. Frontiers in Urban Water Management:
Deadlock or Hope. IWA Publishing, pp. 229-263.
Muschalla, D. et al., 2008. The HSG Guideline Document for Modelling Integrated Urban
Wastewater Systems. 11th International Conference on urban Drainage, Edinburgh,
Scotland, 2008, pp.1-10.
Rauch, W. et al., 2005. Integrated approaches in urban storm drainage: where do we stand?
Environmental management, 35(4), pp.396-409.
Schutze, M., Butler, D. & Beck, M.B., 2002. Modelling, Simulation and Control of Urban
Wastewater Systems, London: Springer.
Vlachos, E. & Braga, B., 2001. The challenge of urban water management. In C. Maksimovic
& J. A. Tejada-Guibert, eds. Frontiers in Urban Water Management: Deadlock or
Hope. IWA Publishing, pp. 1-36.
Wong, T. & Eadie, M.L., 2000. Water sensitive urban design - A paradigm shift in urban
design. In Proceedings of the Xth World Water Congress, 12-16 March 2000.
Melbourne.
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