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RESEARCH ARTICLE
Advanced Science Letters
Vol. 23, 1407–1411, 2017
Blocked Drains Syndrome: Physical Degradation of
the Storm Drainage System in a Compact City
Dedimuni Charmaine Nadeesha Chandrasena1∗, Khamaruzaman Bin Wan Yusof1,
Veranja Chandima Liyanapathirana2, Muhamad Raza Ul Mustafa1, and Zahiraniza Mustaffa1
1Department of Civil and Environmental Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610, Perak, Malaysia
2Department of Microbiology, University of Peradeniya, Sri Lanka
This concept paper describes the behavior of a clogged drain in an event of a heavy rainfall. Solid waste
accumulates in drainage systems, heavy rainfall, increased runoff volume and stagnation of runoff flow could
collectively lead to sudden flash floods in compact cities. Events leading up to a flash flood attack in a city show
a marked similarity to the cascade of events leading to a heart attack. Accumulation of fat in coronary arteries
restricts the blood flow to the cardiac tissue. When the arterial occlusion is beyond a critical level, myocardial
death occurs. This condition is commonly known as a “heart attack.” The clinical solution for this is known
as coronary artery bypass grafting. As such, this paper urged for a novel technical solution which, could be
introduced to reroute stagnated water flow in a clogged drain with the objective of treating the socioeconomic
impact of “Blocked Drains Syndrome.”
Keywords: Clogging, Blocked Drains, Flashflood Attack, Heart Attack, Coronary Arteries Bypass Grafting,
Smart Storm Drainage, Solid Waste.
1. INTRODUCTION
1.1. Why Drainage Fails in Compact Cities
One-fourth of the world’s urban population lives in informal
settlements.1The majority of the informal settlements spread in
hazard-prone areas in low-lying lands due to higher property
prices. As UN-Habitat estimated in the World’s Cities 2012/2013
report, this tendency is expected to grow in the next decades since
increasing migration rates of low-income immigrants into cities.
Settlers in informal habitats hit hardest from natural hazards,
especially flash floods that may attack an area without pre-
warning.2Storm water runoff control is the crucial purpose of
any urban drainage system. The inadequacy of which, is consid-
ered as the main cause of flash floods.3–6 Unplanned urbanization
and rapid development taking place in compact cities have cre-
ated complicated issues in storm water management. On the one
hand, solid waste leads to street floods and it will again generate
a massive stock of solid waste as flood debris.4
Tucci7has examined issues pertaining to the drainage system
in third world countries of the humid tropical climatic region for
decades. According to his research findings, the majority of the
urban squatter settlements scattered in low-lying areas which are
highly environmentally sensitive reservations most of the times.
These shelters made out by improvised building materials and
constructed without legality.478Hence, Municipal authorities
∗Author to whom correspondence should be addressed.
not bound to provide basic infrastructure facilities such as water
and power supply, garbage collection and storm drainage main-
tenance. Therefore, the settlers have no proper place to dis-
pose garbage instead of the nearby open of spaces and roadside
reservations.
This paper is organized as follows. In Section 2, concept of
the blocked drains syndrome thoroughly explained. In Section 3,
experimental scenario pertaining to the research is presented. The
experimental results, case study analysis and the discussion are
also presented in Section 4. Finally, our intention of this paper is
summarized in the conclusion.
2. CONCEPT OF BLOCKED
DRAIN SYNDROMME
2.1. Observed Physical Characteristics of a Low
Income Urban Settlement in a Compact City
The informal settlements in low and lower middle income coun-
tries has comprised with unique spatial features with compared
to other areas. These areas have a considerably higher building
density. Exterior building strip often faced to an access road but it
did not network throughout the area since it has been encroached
at many parts. Sideway building line usually located on a river
bank, canal bank or edges of a receiving water body. Natural and
artificial drainage paths are usually being encroached or blocked
by illegal structures. Hence, storm water did not drain away grad-
ually after a rainfall.
Adv. Sci. Lett. Vol. 23, No. 2, 2017 1936-6612/2017/23/1407/005 doi:10.1166/asl.2017.8388 1407
RESEARCH ARTICLE Adv. Sci. Lett. 23, 1407–1411, 2017
Many researchers specifically mentioned about how the urban
forms correlates with the personal behavior. As Handy9pointed
out, built environment has a significant influence on the behavior
of people. People, who live in compact and congested settle-
ments, suffer immensely from the scarcity of productive space.
Most of the time, they lives on or closer to the open drainage
line. Due to the limited mobility caused by the immediate sur-
roundings, they adapted to a finite routing though it again leads
to a massive set of social and environmental issues. People often
dispose household garbage, gray water, sewerage and other throw
away materials to the nearby open drain. It has observed that the
drainage lines found under their shelters was always filled with
waste particles and gray water.
People lives in and around the tenement garden, have not pro-
vided with door to door garbage collection service. They usually
dump household waste at the nearby garbage collection points.
These points often equipped with medium size waste contain-
ers, which capacity varies from 0.25 ton to 0.5 tons. However,
in most cases, Municipal councils provide permanent collection
points constructed by cement and bricks, which not exceeds 2 m3
in capacity. Generally, this capacity not sufficient to accommo-
date whole amount of waste dumped in to a respective collection
point. Hence, haphazardly dumped waste bags make havoc around
the municipal garbage collection points located in informal set-
tlements (see Fig. 1). Provision of additional waste containers is
again not a proper solution, since the scarcity of effective roadside
space and the inefficiency of the collection services.
Municipal garbage collectors unload the waste containers and
emptying the bricked containers once a day, but it is not possible
to keep the place fully clean until their next visit. Uncollected
and dropped waste matter normally destined at nearest open drain
especially, after a mild rainfall. Generally, the municipal work-
ers not cleaning the roadside drains or clear the drainage line
blockages since their main focus only on the waste collection
service. Clogged waste particles in the micro drainage channels
flushed frontward, up to the secondary and primary drainage
channels as a result of a heavy rain. Due to this, the nearest water
body receives massive stock of uncollected municipal garbage.
This leads to decrease its effective basin capacity and become a
probable cause of a sudden flashflood attack even during a mild
rainfall.
Fig. 1. Garbage dumping point at Khira Nagar Industrial Estate, Mumbai,
India.
Source: http://www.mid-day.com/articles/mumbai-heres-how-bandra-khar-
santacruz-residents-cleaned-up-their-act/15907189 #sthash.vW7y7ZXQ.dpuf.
2.2. The Blocked Drains Syndrome
Blocked Drains Syndrome is a physical disorder creates by
blocked storm drainage system in low lying flood prone area of
a city. A group of symptoms, for instance solid waste accumu-
lated drainage, heavy rainfall event, increased runoff volume and
short flood peak times consistently occur together and lead to a
massive flood impact in the obligated area.
2.3. The Symptoms and Signs of the Syndrome
2.3.1. Arterial Blockages
Occlusion of the arteries in the heart muscles, as well as the
drainage system in a compact city, has the same causal factors
of its fatalist inefficiency. Misbehavior of humans causes dam-
ages and blockages in both vascular system and urban drainage
system.
Epidemiological studies have provided clear evidence to asso-
ciate smoking and bad food habits with almost all forms of the
arterial disease.10 Medical researchers have confirmed that dam-
age to the innermost lining of blood vessels, the endothelium,
and endothelial dysfunction is mainly due to human misbehav-
iors. Causal factors such as tobacco combustion products, high
blood cholesterol, sugar levels and high blood pressure are the
initiators for the cascade of events leading to arterial occlusion.
Endothelial damage and dysfunction lead to the accumulation
and activation of platelets and monocytes. As Powell10 men-
tioned, harmful changes occurring within these cells, possibly
leads to the accumulation of fat and further cells within a lattice-
shaped fiber network of the extra-cellular matrix. This builds up
could be equated with a collection of waste material. As the
plaque builds up, the arterial lumen slowly narrows and the wall
hardens. Moreover, it minimizes the full capacity of the blood
vessel (see Fig. 2).
Damaged arteries cannot deliver adequate blood supply to
the heart muscles or the myocardium.10 A sufficient myocardial
blood supply is crucial for the delivery of oxygen and nutrients
for the cells. Furthermore, for the removal of waste products like
lactic acid and oxygen free radicals. Partial arterial blockage and
the subsequent damages to heart muscles are known as ischemia.
When the arterial occlusion is beyond a critical level and the
blood supply to a given region ceases and myocardial death or
infection occurs, leading to the situation commonly identified as
a heart attack.
Fig. 2. Blocked coronary arter y.
Source: http://www.kumed.com/heart-care/diseases-and-treatments/coro-
nary-artery-disease.
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RESEARCH ARTICLEAdv. Sci. Lett. 23, 1407–1411, 2017
2.3.2. Drainage Line Blockage
Events leading up to a flash flood attack show a marked similar-
ity to the cascade of events leading to a heart attack. Haphazard
dumping of solid waste makes drainage an extremely complicated
issue for compact cities. Urban drainage systems in these cities
are often filled with garbage and sediments (see Fig. 3). Settlers
tend to dump their solid waste into the nearest drain.511 This in
turn decreases its effective drainage capacity.12 Blocked drainage
causes overflowing of runoff water and stagnation in low-lying
areas of the cities. At a heavy rainfall event, it cannot discharge
runoff water to the receiving water bodies on time. Breaking the
smooth flow of discharging runoff water will happen throughout
the system. This situation increases water stagnation, peak flow
disorders and decreases the flood peak attaining time of the runoff
flow. This is when a sudden flash flood attack occurs.
In medicine, Coronary artery bypass grafting is used to restore,
blood flow to the heart muscle by diverting the flow of blood
around the blocked section of an artery. With Smart Storm
Drainage concept, it designed a second channel to divert runoff
water to make an uninterrupted flow. Installation of smart storm
drainage unit to a selected point of a clogged drainage system is
very similar in principle to re-routes the blood flow of the heart
by bypassing the blocked regions.
2.4. Economy of Blocked Drain Syndrome
Storm water runoff control is the key purpose of any urban
drainage system. The Inadequacy of which is considered as one
of the main causes of street floods which leads to flash flood.2313
The costs of street floods are high. It adversely impacts on peo-
ple’s lives, assets and the economic productivity. As City of Texas
Austin Urban Drainage manual stated14 tangible costs such as,
destruction of buildings and physical infrastructure, mechanical
failures of vehicles, and the cost of health care are considered as
crucial facts which causes most economic losses. It also involved
a considerable amount of intangible damages, for instance, aes-
thetically unpleasant environments, spreading of vector-borne
diseases, congestion and traffic flow diversion. These symptoms
are considered as the consequences of doing nothing and will
expose an unprepared city into long-term risks of floods.
Fig. 3. Clogged micro drainage at Dhaka, Bangladesh.
Source: http://globalchallenge.mit.edu/problems/view/69.
3. METHODOLOGY OF THE RESEARCH
Three experimental scenarios were created which replicates the
present situation of the micro drainage system described in the
literature. Roughness coefficient values pertaining to the each
case were obtained from the Manning’s “n” values suggested
by Chow15 for different drainage conditions which stated in the
Table III.
The total litter load in a clogged drainage channel was cal-
culated and the effective drainage capacity pertaining to the
case study area was determined accordingly. Then, the effective
drainage discharge rates Qcof each experimental scenario were
calculated and the peak runoff rate Qrof the given sub catch-
ment was computed. All the values (Qcand Qrwere compared
in order to find the magnitude of the clogging effect and the
effective drainage capacity in an event of a moderate rainfall.
3.1. Calculate the Clogging Percentage of the
Micro Drainage Line
The total litter load clogged in micro drainage channels is given
as Ref. [16]
T=fscivi+Bi·Ai(1)
where Tis the yotal litter loads clogged in micro drainage chan-
nels (m3/yr), fsci is the street cleaning factor each land use (this
number varies from 1.0 for regular street cleaning to about 6.0 for
non-existent/complete collapse of service), Viis the vegetation
load for each land use (varies from 0.0 m3·ha ·yr to poorly veg-
etated areas to about 0.5 m3·ha ·yr for densely vegetated areas),
Biis the basic litter load for each land use and Aiis the area of
the each land use (ha).
However, the constant values assigned in the original formula
were slightly modified to fit with the objectives of this study.
The original formula developed by Armitage and Rooseboom16
put more weightage on commercial and industrial waste circulat-
ing in the area but the present study thoroughly focused on the
residential waste that circulate in the settlements of the compact
cities. Hence, the value of Bi, basic litter load for each land use
was reweighted as follows taking into consideration the average
Municipal solid waste generation rate and the basic litter load
left uncollected in the different settlement areas. These values
extracted from the literature pertaining to this study.517
3.2. Calculate the Effective Drainage Discharge Rates
Effective discharge rate of the micro drainage line which serves
the study area is given as;
QC=1
nAR2/3S1/2(2)
Qc=effective discharge capacity of the drain m3/s
n=Roughness coefficient pertains to the micro drain
A=effective unit area of the flow (m2)
Table I. Values assigned for basic litter load uncollected for each set-
tlement (Bi).
Low income informal settlements 05
Middle income condominium settlements (high-rises) 03
Middle income condominium settlements 03
(single units-attached)
Common settlement area located in the urban rural fringe 02
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RESEARCH ARTICLE Adv. Sci. Lett. 23, 1407–1411, 2017
Table II. Total litter load in the drain.
Total litter load in 502+0516539 =579 m3
the drain
Total drainage capacity 151.52 m ×0.45 m ×0.3 m =2045 m3
% clogged 27%–30%
P=effective wetted perimeter (m)
R=effective hydraulic radius (m)
S=bed gradient of the drainage.
3.3. Calculate the Peak Runoff Pertaining to a
Given Area
The Rational formula is used to compute the peak runoff rate at
the point of design.
Qr=1
360 CiA (3)
where,
Qr=peak runoff at the point of the design (m3/s)
C=runoff coefficient
I=average rainfall intensity (mm/hr)
A=catchment area (ha).
3.4. Description of the Case Study Area
The selected sub catchment is located in Madampitiya GN divi-
sion of Colombo 15, Sri Lanka. This is an informal settlement
area with 1.6539 ha land parcel where nearly 75% of the land is
occupied by low income housing units. The micro drainage chan-
nel of this area is 151.52 m long, 0.45 m deep and 0.3 m wide
and is present uniformly along the channel. The area receives
average rainfall intensity of 20 mm/hr.
4. RESULTS AND DISCUSSION
According to the total litter load computation mentioned in
Table II, the micro drainage channels located in the sub catch-
ment area are clogged with solid waste and sediment for about
30% of its capacity throughout the year. Hence the effective
drainage capacity is computed as 70% of the total drainage
capacity. Effective drainage discharge rates pertaining to the each
case are figured in Table III. If the drainage channel is clogged
about 30% of its total capacity, its discharge rate decreased into
a very low level (0.01 m3/s) due to the reduction of the effective
drainage capacity and the increase of the resistance to the flow
(Manning’s n). Perfect drainage scenario or the control case was
mentioned in case 3, which was able to convey a flow rate fif-
teen times greater than the clogged drainage scenario. However,
this cannot be achieved in a practical state since the unavoidable
sedimentation and the clogging effects.
Table IV represents the changes of the peak runoff rates with
the average rainfall intensity values recorded throughout the year.
Table III. Effective drainage discharge rates Qcpertaining to th e each case.
Experimental Effective Effective Effective Qc
scenario Description Manning’s nA(m
2P(m) A/P=R(m) (m
3/s)
Case 01 30% clogged, no trap 0132 009 0901001
Case 02 0% clogged, with a trap 0046 0135 1201125 004
Case 03 Control case 0014 0135 1201125 015
Table IV. Peak runoff rate pertaining to different rainfall intensities.
Rainfall intensity (mm/hr) Qr (m3/s)
20 007
19 007
18 006
17 006
16 006
15 005
14 005
13 004
12 004
11 004
10 003
9003
8003
7002
6002
5002
4001
3001
2001
1000
Calculated results pertaining to the equation 01, has showed
the drainage channels situated in the case study area carried
about 30% litter capacity throughout the year. It is clear that the
drainage channel situated in the case study area cannot handle
the overland flow generated by rainfall intensities greater than
5 mm/hr since it exceeds the present carrying capacity of the
drainage channel (see case 01, Table III).
In this situation, micro drainage channels tend to overflow eas-
ily even after a mild rainfall which brings 5 mm/hr rain. If the
case study area receives a rainfall greater than this intensity
(5 mm/hr), it may results an intense flash flood attack followed
by blocked drainage channels.
5. DISCUSSION
Blocked Drain Syndrome can socially and economically paralyze
an unprepared city at any moment. These types of socio-
economic losses cannot easily bear by the vast majority of com-
pact cities. Therefore, compact cities with inefficient drainage
infrastructure should have to prepare to handle upcoming natural
disaster risks.
Dredging and cleaning are a conventional method which
used to clear a clogged storm drainage channel. It involves
heavy machinery, for example, hydro-pneumatic flow jets, metal-
lic strings, rollers and vacuum tankers.18 Since this process is
manually operated, it also involves much manpower and time.
As Parkinson18 mentioned, the manual cleaning efficiency of a
clogged drainage channel is about 15 km/per month.
New urbanists believe that they can change the human behav-
ior through design. The situation discussed above, pertains to
the informal settlements, have explored some crucial facts to be
addressed in new a drainage design initiative. As a minimum, even
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RESEARCH ARTICLEAdv. Sci. Lett. 23, 1407–1411, 2017
the outskirt of the informal settlements needs an extended waste
trapping mechanism throughout the existing micro drainage line
to prevent clogging. There’s an urgent need of maintaining a clear
channel to facilitate fast conveyance of storm water which prevent
unnecessary stagnation. In a situation of a clogged drainage chan-
nel, it is advisable to re-route the water cause even with a tem-
porary external channel. There needs to be a mechanism which
facilitates municipal garbage workers for easy removal of flushed
and fallen garbage from the drainage line. Since, dredging and
cleaning of the drainage canal is not under the duty of municipal
garbage collectors.
6. CONCLUSION
Drainage network is a key element that manages the storm water
circulation of a city. The inefficiency of which will cause severe
system breakdowns that lead to harmful socioeconomic and spa-
tial impacts. Blocked drains physically degrade the drainage
infrastructure and put the compact city into an unprecedented
danger. Uncontrolled forces like heavy rainfalls can trigger the
harmfulness of this situation. The risks of natural disasters are
expected to be increased over the next few years. Therefore, com-
pact cities should have a proper preparedness plan over upcoming
threats. Whenever a drainage channel appears to be clogged it is
advised to clear a channel or re-route the flow to allocate a path
for the runoff. This is what the coronary artery bypass grafting
does, when the arterial blockage occurs.
Acknowledgments: The authors wish to thank Dr. Janaka
Kumara (Post-Doctoral fellow at Meijo University Japan),
Dr. Lakshan Abeynaike (MD), Dr. Gayan Abeygunawardhena
(MD) for reviews of drafts.
References and Notes
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ledge (2013).
2. A. K. Jha, et al., Cities and Flooding a Guide to Integrated Urban Flood Risk
Management for the 21st Century (2012).
3. A. K. Gupta and S. S. Nair, Current Science (Bangalore) 100, 1638 (2011).
4. C. E. Tucci, Urban Drainage in Humid Tropics 23 (2001).
5. J. Lamond, et al., The Role of Solid Waste Management as a Response to
Urban Flood Risk in Developing Countries, A Case Study Analysis (2012).
6. S. Cairncross, et al., Poor die young, Housing and Health in Third World
Cities, Earthscan (1990).
7. C. Tucci, Urban drainage in humid tropics, Volume I in Maksimovic, C, Urban
Drainage in Specific Climates (2001).
8. D. C. N. Chandraseana, et al., Jurnal Teknologi 78 (2016).
9. S. L. Handy, et al., American Journal of Preventive Medicine 23, 64 (2002).
10. J. T. Powell, Vascular Medicine 3, 21 (1998).
11. S. Gupta, et al., Resources, Conservation and Recycling 24, 137 (1998).
12. C. Zurbrugg, Urban solid waste management in low-income countries of Asia
how to cope with the garbage crisis, Presented for Scientific Committee
on Problems of the Environment (SCOPE) Urban Solid Waste Management
Review Session, Durban, South Africa (2002), pp. 1–13.
13. M. A. Taleb, Global Journal of Human Social Science, Geography and Envi-
ronmental GeoSciences 12, 37 (2012).
14. C. O. A. Watershed Engineering Division, Meredith Street Storm drain
Improvement Project Preliminary Engineering Report, Government of Texas
(2013).
15. V. Te Chow, Open Channel Hydraulics (1959).
16. N. Armitage and A. Rooseboom, The removal of urban litter from stormwater
conduits and streams, Paper 1—The Quantities Involved and Catchment Litter
Management Options, edited by S. A. Water (2000), Vol. 26, pp. 181–188.
17. A. M. Troschinetz and J. R. Mihelcic, Waste Management 29, 915 (2009).
18. J. Parkinson and O. Mark, Urban Stormwater Management in Developing
Countries, IWA Publishing (2005).
Received: 3 June 2016. Accepted. 31 July 2016.
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