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LETTER | Maximise use of retention ponds to stop flooding in urban areas

LETTER | Climate change is going to wreak havoc worldwide in the future as global damage has already been done to the earth's fragile ecosystem. It will take decades to reduce its negative impact, if at all.

Malaysia with its equatorial climate will be one of the worst-affected in the future. There is no way to stop overflowing large rivers in Pahang, Kelantan, Perak or Johor, whose volumes swell after very torrential seasonal rains.

People have learnt to live with the yearly floods in these states. However, in the last few decades, logging and the clearing of large areas of forest in various parts of the country have led to a paradigm shift in the occurrence of floods and the damage they cause.

The only ways to overcome floods will be to drastically reduce logging activities and also relocate people to higher ground in new settlements in some of these states. Both steps are within the capabilities of both state and federal governments.

Retention ponds should also be built in logging areas to reduce the run-off and silting of streams and rivers. Since the excavators are already operating in the logging areas, it will be easy to dig retention ponds in low-lying areas depending on the configuration of the land.

Speedy rehabilitation and re-afforestation of logged areas must be done. Fast-growing creepers, weeds, saplings and other plants can be introduced in the logged areas to prevent erosion. Part of the timber concession fee should be for rehabilitation of the logged areas.

The government should also look into the possibility of building barges across rivers that can hold back water and silt. Small retention dams whose only purpose is to hold back water can be built across the higher reaches of various rivers. The dams can be emptied when necessary during and after the rainy season.

These are just some common-sense measures to stop the incessant annual flooding that causes much hardship to the riverine folks and others, as well as causing massive damage to infrastructure.

In highly urbanised areas such as Selangor or Kuala Lumpur, the most effective way is to ensure that every housing or industrial estate has retention ponds to contain the run-off and not contribute to flooding lower down the river.

Retention ponds must be compulsory and not left to the discretion of the developers. The terrain of the Klang Valley is generally flat and rivers will overflow when the volume of water increases with heavy downpours. The only logical way is to reduce the run-off leading to the rivers and swelling it.

Better still, large housing areas can have recreational lakes to contain the heavy downpours. This can be done through necessary earthworks and landscaping. Residences around these lakes can fetch a high price, which can be an incentive to the developers to excavate large lakes to hold the run-off.

The retention ponds must also be properly maintained. I have seen some retention ponds where large trees have grown over the years and were clogged up with garbage of all kinds.

These retention ponds will serve no purpose. They need to be dredged and cleared of garbage when necessary. Every local authority in Selangor must see to it that retention ponds are well maintained.

Since rain harvesting is not gaining ground among the developers as well as residents then the best alternative is retention ponds. In every local authority in Selangor there must be a small team in charge of the retention ponds to ensure that the system is functioning well.

Every residential area, whether on higher ground or otherwise, must have retention ponds to ensure that the streams and rivers do not flood housing areas and industries lower down the river.

In Selangor, which has become one huge concrete jungle and the urban sprawl not showing any sign of letting up, the only way to avert both flash floods and floods is to opt for retention ponds which can be invaluable in averting floods if well planned and maintained.

The Taman Sri Muda residential area would not have been flooded so severely if the nearby housing estates, some of which are upscale affluent residential enclaves, had retention ponds and lakes of their own, which should have been compulsory.

The run-off from the housing areas nearby ended up in Sri Muda, which then created an unprecedented deluge that caused widespread suffering and hardship, not to mention the loss of lives and damage to property, which has been estimated to exceed RM1 billion.

The views expressed here are those of the author/contributor and do not necessarily represent the views of Malaysiakini.

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