Background

The Klang Valley is the most developed area in Malaysia, especially at the city of Kuala Lumpur. Due to the rapid development and urbanization, flooding problems in the Kuala Lumpur city center have become more frequent and severe. It has been recognized that from the flooding events happened on 26th April 2001 dan 29th October 2001, the Sungai Klang stretch between Tun Perak bridge and Dang Wangi bridge is badly flooded where the channel capacity is insufficient to cater for the flood flows. The situation is compounded by constrictions at various bridge crossings especially at the Tun Perak bridge and blockages. However, it does not mean that the other tributaries are sufficient to cater for the flood flows. It so happened that during the 26th April 2001 and 29th October 2001 flood events, both rainstorms occurred at the north-east of the catchment where flood runoff is drained by the Sungai Ampang and the upper Sungai Klang. The other tributaries that flow through the Kuala Lumpur city are also in critical conditions and required immediate flood mitigation solutions. Among the more critical ones are the Sungai Gombak and Sungai Batu, which are located on the north-west portion of the catchment. The confluence of Sungai Klang and Sungai Gombak is at the Masjid Jamek. In fact, the flood flow contribution from the Sungai Gombak catchment is higher than the upper Sungai Klang catchment due to larger catchment area if similer rainfall occurs on both catchments. In terms of degree of urbanization, both Sungai Gombak and Sungai Klang are comparable. If the same rainstorms as the 26th April 2001 and 29th October 2001 events occur at the Sungai Gombak and Sungai Batu catchment, the city area adjacent to these rivers will also encounter similar flooding situation as have happened along Sungai Klang.

1.0 : Introduction 

Flooding in general is caused by the inability of water to flow away rapidly from an area due to certain factors, causing a build-up of volume and thus creating floods. In the case of Kuala Lumpur, these contributing factors include extensive development along both sides of Kuala Lumpur river banks, the presence of ‘bottlenecks’ in the river in the form of bridges and supporting piers, and last but not least, the condition of the current drainage system which is no longer suitable in handling the advent of torrential rains.

2.0: Objective 

The objective of the project is to provide a Flood Mitigation scheme to protect the City area along Sungai Gombak and Sungai Batu in the event of 1 in 100 years return period flood. The strategy of the project is to divert flood discharges from Sungai Gombak and Sungai Keroh into the Batu Detention Ponds respectively to reduce the river flows in the City during flood. 

3.0: Scope of Work 

The scope of work consists of the construction of Batu and Jinjang Flood Detention Ponds, Flood Diversions and Associated Structures on a Design and Build basis. The details of the works are:

1) Gombak Diversion Scheme

• To construct a barrage across Sungai Gombak.
• To upgrade and enlarge the existing Gombak Diversion channel thereby increasing its discharge capacity from 60 cumec to 275 cumec.
• To enlarge Batu Detention Pond thereby increasing storage volume to 4.5 million m3.
• To construct associated structures such as trash screen, inlet and outlet gates. ogee weir, bridges, flood walls, local drainage works, control rooms, quaters, maintenance ramps, inspection chambers and etc.

   

   

2) Keroh Diversion Scheme

• To construct a barrage across Sungai Keroh.
• To bund the Sri Segambut Pond as inlet regulation pond.
• To construct diversion channel for discharge capacity of 100 cumecs.
• To enlarge Jinjang Ponds increasing storage capacity to 2.5 million m3.
• To construct associated structures such as trash screen, inlet and outlet gates. ogee weir, bridges, flood walls, local drainage works, control rooms, quaters, maintenance ramps, inspection chambers and etc.

4.0 : How the system works 

Here’s how the system works. When an impending flood is detected for the Gombak Diversion, a sequence of gate operations will be triggered to divert the Gombak river floodwater away from KL towards the Batu Pond. This is accomplished via the Gombak Diversion Channel which is 3.5 kilometers long, 26 meters wide and about 4 meters deep. The channel, which is a combination of fully-covered, partially covered and fully-opened sections, is done in that manner to comply with the requirements of the local authorities, environmental and residential conditions. The maximum conveyance capacity for Gombak Diversion Channel is 275 cubic meters per second and the enlarged Batu Pond has an active storage capacity of 4.5 million cubic meters.
The same also goes for the Keroh Diversion, where a similar system of gates will be triggered to divert the Keroh river floodwaters away from KL towards the newly built Jinjang Ponds. The Keroh Diversion Channel is 2.2 kilometers long and the maximum conveyance capacity is 100 cubic meter per second. The typical channel dimension is 12 meters wide, about 5 meters deep and like its Gombak counterpart, it is a combination of closed and open channels. Closed channels are done due to the fact that some sections run alongside as well as through Jalan Kepong. The unique alignment of the channel is to compensate for the presence of service structures, such as TNB Pylons, Maxis Fibre Optic lines and JBA Water Pipelines, while at the same time minimising land acquisition. The water diverted from Sungai Keroh into the Keroh Diversion Channel will be stored in the Jinjang Ponds, consisting of Nanyang, Wahyu and Delima Pond with a combined storage capacity of 2.5 million cubic meters. 

After the event of rain has receeded and the river flow has come under smoother control, the next phase in the system will be the process of water release. Once the water level near the PWTC area has reached an acceptable mark, the floodwaters which have filled the storage ponds will be gradually released into Batu River and Jinjang River respectively. This is done via the penstock gates which will come into operation within 48 hours after the storm had subsided.

5.0: SCADA System 

For the KLFM Project to work and function properly, an Integrated Flood Monitoring Control and Management system will be provided to manage the water flow on the diversions. Local Control Station and monitoring devices will be installed at strategic points along the river systems, along the diversion channel and at the Controlling Barrages and Gates. The SUPERVISORY CONTROL AND DATA ACQUISITION, or SCADA, comprising of control consoles equipped with strategically installed video surveillance, water-level monitoring devices and several floodgate control systems installed at the water-detour structures will ensure secure and consistent water flow management. The SCADA System will confirm that the installed floodgates work in an orderly fashion to prevent any mishap and damage to the mechanisms involved.

Finally, when all the components have been successfully setup, skilful and well traineoperators will be placed at the control centers to monitor the river flowing through the pathways during flood season and to control the opening and closing of the floodgates as necessary, using the SCADA system. Water level sensors will be placed at designated areas, in order to measure the criticality of the water levels. They will serve as an indicator to trigger the operation of the gates via the SCADA system. This will ensure that the system works perfectly and further prevent any loss of lives and/or property, should any technical errors occur.

The KLFM Project had to be implemented to rid Kuala Lumpur from the perennial headache of preventable floods. The project has begun since August 2003 and expected to be fully completed in November 2009.