KUALA LUMPUR, May 16 — New developments should be restricted from discharging rainwater into the city’s overwhelmed drainage system, The Institution of Engineers, Malaysia (IEM) suggested today.

The group made the “zero additional discharge” suggesting after concluding that rapid development was among the possible factors for the flash flood that struck the city last Thursday.

IEM president Tan Yean Chin said it was possible to cut additional water runoff after development by providing adequate retention ponds for rainwater at the source in development areas.

“New developments should take into account best management practices such as provision of adequate drainage system designed at appropriate protection level and control of water at source principles,” Tan said in a statement today.

“IEM would like to recommend that for new development in the Klang Valley, the zero-additional discharge principle should be imposed to developers as one of the development approval conditions which means to say that new development approved must not contribute to additional surface water runoff after development.”

He said that rainfall causes silt and debris to be washed up and deposited at the outlets of drainage systems causing clogs, and stressed for ongoing developments to adopt a “professional approach” by using official hydrological data in designing temporary drainage system

Tan added there also needed to be more public awareness on dumping of rubbish in drainage systems as well as the need to uplift the maintenance culture of local governments for better drainage system.

“IEM would like to stress that in carrying out flood mitigation measures, there is a need to consider both the structural and non-structural measures that must be implemented under the short and long term development programmes,” he added.

“The non-structural measure lies in the control of land development and all the relevant authorities must be serious in tackling the root causes that leads to major siltation of the drainage system, rivers and waterways.”

Parts of Kuala Lumpur were flooded after torrential downpour last Thursday.

Business owners affected called the floods the worse in the last 30 years and images were circulating online showing Universiti Malaya students’ cars completely submerged.

Natural Resources and Environment Minister Datuk Seri Wan Junaidi Tuanku Jaafar said yesterday that the flash floods happened as the city’s drainage system was not capable of accommodating rainfall intensity of over 80mm per hour.

Last Thursday’s rainfall was recorded to be between 120mm and 140mm per hour for two straight hours.