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CHAPTER 4
BACKGROUND TO THE STUDIES
4.1
Introduction
In the past two years, occurrences of flash floods on a serious level occurred three
times i.e. on 26th April 2001, 29th October 2001and 11th June 2002. On 10th June 2003,
the Kuala Lumpur city centre was again subjected to another serious flash flood
occurrence.
As a result of current constrictions, any work proposal to widen thus increase the
capacity of the Klang river in the city centre would require high-valued buildings to be
demolished, apart from the element of tremendous amount of money would be involved
in terms of land acquisition. Therefore, the proposal to build a Flood Bypass to alleviate
excess flood waters originating from upstream thus preventing floods from occurring in
the city centre was given consideration by the Government.
The Proposal for the Stormwater Management and Road Tunnel (SMART)
Project was identified as the most suitable alternative and the Government has decided
for it to be implemented as soon as possible. The Government has issued a Letter of
Intent appointing the MMC Engineering Group Berhad - Gamuda Berhad JV Consortium
to implement this project. For the current situation, the project already started with
MMC-Gamuda implementing this project.
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The Smart Project involves the diversion of flood runoff from the catchment area
(near the confluence of the Klang River and the Ampang River) through a bypass tunnel
before it is being directed back to the Klang River downstream. The Tunnel also provides
an alternative traffic route to lessen traffic congestion at one of Kuala Lumpur's southern
gateway near the Sungai Besi Airfield.
4.2
Scope Of Work Of SMART Project
The scope of work involved in the SMART Project consists of these main components:
The Bypass Tunnel is 9.7 km in length originating from upstream of the Klang
River in Kampung Berembang, Ampang reaching southward and ended in an exmining pond in Taman Desa, Sungai Besi. It has an internal diameter of 11.8 m.
Apart from the construction of the tunnel, the stormwater management components
consist of:
1. The construction of a holding basin in Kg. Berembang, in the Gombak district Kg.
Berembang, Gombak district
2. The upgrading of an ex-mining pond in Taman Desa as a pond the construction of
a twin box culvert outlet structure (about 500 m in length) from the Taman Desa
pond to the Kerayong river;
3. The upgrading works of the Kerayong river (about 1.8 km in length)
4. The construction of related control structures
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Upon completion, the ponds and the bypass tunnel will have the capacity to store
3.0 million cubic metres of floodwater. A portion of the tunnel (about 3 km in length)
will integrate both flood mitigation management and roadway purpose. This dual-usage
portion begins from the Kg. Pandan Roundabout and ended at the KL-Seremban
Highway near the Jalan Istana junction.
The roadway component in the SMART Project comprises of a double-decked
carriageway in the tunnel (refer 'Figure 4.2' below). The Ingress and egress to the existing
roadway system are connected to Jalan Tun Razak (1.4 km) and to the KL-Seremban
Highway (1.6 km). A flood detection system will be integrated in the SMART system to
manage traffic control operation and flood forecasting.
Figure 4.2: Typical Cross Section of SMART
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The SMART Project is scheduled to be complete in four years time; construction
work has begun since November 2002 and expected to be completed in the end of 2006.
4.3
The Klang River System
Kuala Lumpur is situated in the mid upper reaches of the Klang River. The river
drains catchment of approximately 1,288 sq km. It originates from the Main Range at an
elevation of 1,330 meters above mean sea level and traverses a distance of nearly 120km
through the two States, Selangor and Wilayah Persekutuan, before discharging into the
Straits of Malacca.
The river’s headwaters comprise mountainous and steep terrain that for the most
parts is covered by a thick canopy of tropical jungle. At the mid upper reaches where KL
is situated are lands generally less steeper and between 30 and 60 meters above mean sea
level. The area is mostly built-up land of township, residential estates and industrial
parks. It is by far the most heavily populated part of the basin. The principal tributaries of
the Klang River System namely the Batu, the Gombak and the Ampang Rivers join the
main river at this stretch.
The river downstream of KL flows through gently rolling lands and a flat coastal
plain before discharging into the sea. The rolling grounds have mostly been converted to
agriculture lands for estate type planting of commercial crops such as rubber and oil
palm. The flat grounds fronting the coast, which have significant parts below high tide
levels, are dyed at many such locations and provided with improved drainage to enable
the cultivation of crops such as rubbers, oil palm and coffee. In recent times there is
observed a movement to buy over the estate lands and have them developed into new
townships and residential areas.
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This process of land use conversion is expected to be a feature for some time in
the foreseeable future. For all intends and purposes therefore the Klang River catchments
is in a dynamic state of constant change through development activities that would keep
altering its hydrological and geomorphologic feature for some time yet to come. About
3.75 million people presently populate the river basin.
4.4
Flood Trends Observed in KL City
KL, as was stated earlier, straddles the confluence of the Gombak Rivers. The
area is known as the Upper Klang Valley and is the most heavily urbanized and densely
populated part of the country. By virtue of its central location and stature of being the
nation’s capital city, KL’s already robust commerce and business activities are under
constant pressure for further expansion. To meet these expectations, developers are
drawn in to provide more and more office spaces and housing into what is already a
congested space. In response to this, City Hall has had to have its public services and
amenities periodically upgraded to keep abreast of developments.
This constant action and reaction has resulted in the roofed area over and near KL
being significantly increased. It has also led to the emergence of extensive and new
network of road systems and new forms of public transportation (the LRT and the
Monorail) systems being introduced. The net impact from all of the above was to turn
greens into paved areas and to overtax the already stressed out city reserves that were
originally placed for infrastructure. In the wake of this activity, a number of drainage
reserves at key locations have been encroached by the expanding building and other
infrastructure fronts.
KL has experienced fourteen major flood incidences in its history (Table 4.4). Of
those major floods, seven have occurred in the past 8 years. The earliest recorded incident
was the flood in 1926.
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Table 4.4: Flooding Incidences in KL City
PERIOD
NUMBER OF TIMES
DATES
Before 1950
1
1926
1950 to 1975
1
1971
1976 to 1985
1
1982
1986 to 1995
4
1986, 1988, 1993, 1995
7
1996, 1997, 2000, Apr
1996 and now
2001, Oct 2001, Jun 2002,
Jun 2004
Whilst from the foregoing it can be observed that KL has indeed a long history of
flooding, what is alarming is that the incidences of these flooding have been of late more
frequent, especially so in the last decade.
4.5
The Government’s Master Plan for Flood Control in Klang River Basin
In 1978, the Malaysian Government engaged a study to understand the flood
problem in the Klang River Basin and how to respond to it.
4.6
Forms of Flooding in Klang River Basin
The Study identified two forms of flooding that affected the Klang River Basin.
The first was monsoonal type flooding caused by long duration (3 to 10 days) of low
intensity rainfall (20mm/hr or so), precipitating over a large area. It was observed that
such weather condition usually is the basis for flooding in the bigger tributaries and the
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main river channels where the size of the contributing catchments is substantial. Floods
arising from this form of rainfall can be quite serious as it is not only widespread but it
also long lasting (usually a few days at least). The impact of monsoon type storms is
smaller tributaries and the storm water drainage network however is not particularly
significant, as storm volumes produced by the smaller catchments in these locations are
not sizeable enough. The 1971 flooding was a monsoon type flooding.
Flooding of the second type is caused by thunderstorms which are localized
rainfall of very high intensities (>180mm/hr) and short durations (2 to 5 hours). The
intense level of precipitation during such storms usually causes large volumes of storm
run-off even from small catchments, which often leads to drainage and river systems in
the localized areas being completely overloaded. This causes what is termed as flash
flooding. As the name would suggest flash floods are quick to manifest after a storm and
equally swift thereafter to subside. The flooding rather than being spread is confined to
specific locations and is gone within a few hours.
The Study identified that flash flood is the form of flooding frequently
experienced in KL and can happen several times each year.
4.7
Flood Mitigation Program for Klang River Basin
The Government’s action for immediate control was the implementation of the
Klang River Basin Flood Mitigation Project (KRBFMP). It was designed to provide flood
protection of up to the 1 in a 100-year event to the lands in the Klang River System. To
achieve the objective the following strategy was adopted:
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4.8
Flood Mitigation Strategy for Klang River Basin
i.
Provide upstream flood detention where feasible
ii.
Undertake channel improvement works at flood prone locations
iii.
Dyke up low grounds with the provision of pumping facilities for their
hinterland drainage
iv.
4.9
Implement inter-basin transfer of flood waters if this is feasible
Klang River Basin Flood Mitigation Project (KRBFMP)
Government chooses to implement the KRBFMP in two phases:
In the first phase:
i.
The Klang Gates dam would be raised by 3.05m for flood storage
and attenuation purposes
ii.
The Batu dam (4.8million cubic meter storage) would be
constructed at the headwaters of the Batu River to regulate flood
discharges emitting from this catchments
iii.
Selected river improvement works at priority locations (Refer
Table 4.9a) would be carried out to upgrade channel capacities at these
locations.
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Table 4.9a: Phase 1 River Improvement Works
River
Length
Klang
33.7
Location
Ulu Klang Bridge to Puchong Drop
Gombak 8.1
Kampung Tangut to Klang River confluence
Batu
Ipoh Road Bridge to Gombak confluence
5.5
The objective behind carrying out the above works was to bring relief to the mid
Klang River Basin, the area considered as requiring immediate attention. This phase of
the KRBFMP is now fully implemented.
Phase II of the KRBFMP comprised the following works:
i.
Construction of the Batu Detention Pond
ii.
Construction of the Gombak Diversion Channel
iii.
Conversion of swamps as Flood Retarding Basins
iv.
Removal of the Puchong Drop
v.
Channel improvement works at Klang, Gombak and Batu Rivers
(94.7km)
vi.
Rehabilitating 10 numbers bridges to increase theirs flood handling
capacities (Table 4.9b)
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Table 4.9b: Phase II Bridge Rehabilitation List
River
No
Bridge Location
Klang River
1
Jalan Tun Perak Bridge
2
Jalan Damai Bridge
Gombak
1
Near Sentul Flats off Jalan Pahang
River
2
Jalan Kampong Puah Sabarang Bridge
3
Jalan Chubadak Dalam Bridge
1
2.5mile Jalan Ipoh Railway
2
Jalan Selvadurai
3
Jalan Segambut
4
Jalan Cenderuh
5
4.25 Mile off Jalan Ipoh
Batu River
The primary target of the Phase II works is the flood prone areas in the lower
Klang River Basin particularly so that these locations do not have their problems
aggravated as a results of Phase I works. Phase II is presently under implementation and
should be fully implemented by 2005.
4.10
Midcourse Appraisal of the KRBFMP
During implementation of the KRBFMP, a series of flood events affecting KL
city center between 1996 and 2000 called to attention a need for an urgent review of the
whole Project. Its effectiveness had to be reappraised, particularly since Phase I works for
flood relief to KL had already been completed and yet the flooding in the city center
seemed unabated.
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The review showed up that:
i. Flood magnitudes in the city had further escalated due to the intensity of land
development. The computed 100-year flood peak at Tun Perak Bridge is
now 460 cumec instead of the original 353 cumec on which the KRBFMP
design had been based.
ii. New constraints had emerged in the river particularly along the stretch
upstream of Masjid Jamek as a result works related to infrastructure
development.
Model analysis of the constraints showed that the 100-year flood level at Tun Perak
Bridge would be 1.76m higher than its original design level of 29.34m LSD bringing it at
this region to be above the general level.
The principal cause for the rise in level was found to be in the conditions where
each bridges capable to handle the floods of their catchments either too low, narrow or
both. These review findings formed the basis that leads to the formulation of SMART.