SHAH ALAM, July 30 — The overall effectiveness of flood mitigation projects in Petaling Jaya, Damansara, and Shah Alam can only be properly assessed once all components have been completed and are fully operational.
State executive councillor for infrastructure and agriculture Dato' Izham Hashim said that the projects are being implemented in phases, whether short-, medium-, or long-term solutions.
Selangor also regularly evaluates the effectiveness of flood mitigation infrastructure in light of ongoing development, land-use changes, hydrological data, and rainfall patterns.
Much of the existing drainage system continues to operate according to its original design, even though climate change has brought increasingly unpredictable rainfall that exceeds its capacity.
He said that urban flooding is generally caused not by a single factor but by a combination of several, including backflow, restricted water flow, sedimentation, obstructions in drainage systems, and exceptionally heavy rainfall beyond the design capacity of existing infrastructure.
The expansion of paved surfaces, coupled with the reduction of green areas and natural water infiltration, has significantly increased surface runoff, causing water to flow more rapidly into drainage systems.
"Changes to the urban landscape, the expansion of paved areas, increasing rainfall intensity, and continued development mean that the capacity of the existing system must be upgraded progressively.
"It must be understood that flood mitigation projects are intended to reduce the risk and impact of flooding, not to eliminate flood risk entirely.
"The overall benefits of these projects can only be assessed once all project components have been completed and are operating in tandem with the drainage systems implemented or upgraded by the local authorities," Izham said.
As such, the state government will continue to make substantial investments in flood mitigation projects, river improvement works, drainage system upgrades, and related infrastructure.
"The government is also encouraging the adoption of nature-based solutions, such as the sponge city concept, in new developments to help reduce stormwater runoff into drainage systems.
"In Petaling, the Irrigation and Drainage Department (JPS) operates 19 rainfall telemetry stations, 11 river level monitoring stations, 18 IP camera units, 25 flood warning siren stations, and seven flood gauges," he said.
Izham also emphasised that efforts to reduce flood risk are not carried out solely by JPS, but involve multiple agencies, including local authorities and the Public Works Department.
