Retention ponds are crucial

Selangor has been prone to flooding for a long time because of rapid development and relentless urban sprawl. Unless drastic steps are taken to address both floods and climate change, these deluges will recur.

Retention ponds play a vital role in controlling excess rainfall. Sadly, retention ponds are among the most neglected aspects of development. With properly maintained retention ponds, there will be less need for alternative, costly flood-mitigating measures.

For example, there are hardly any retention ponds along the Sungai Buloh river, where bridges were recently washed away, and banks were severely eroded near Kampung Kubu Gajah. From Bandar Sri Damansara, various large housing developments have mushroomed over the decades, draining their run-off into the river before it reaches the sea in Jeram near Kuala Selangor. Most developments along the river have no retention ponds, or their existing ponds have silted up, causing the small river to swell into a large, fast-flowing torrent during heavy downpours.

This is the same situation in many housing and industrial developments across Selangor. The Kampung Melayu Subang deluge could have been worse because of major developments around Subang, Kota Damansara, Ara Damansara, and Kwasa Damansara.

Many retention ponds silt up quickly and fill with all kinds of trash. Currently, many of these ponds sit in awkward, narrow, confined spaces, and de-silt them is difficult because even long-armed excavators cannot fully reach the centre. Poor access also prevents full de-silting, as silt cannot be loaded onto lorries for disposal.

Retention ponds need to be rectangular, deep and about 120 ft wide. This will enable present-day extra-long-arm excavators to de-silt them quickly and efficiently from both sides. When an area is developed, the layout, levelling and earthworks should ensure that rainwater run-off ends up in drains leading to the retention pond, from where the water can be drained out the next day.

Retention ponds play a big role not only in preventing floods within housing estates but also in preventing floods in downstream developed areas.

There will be no need for expensive pumps or their operation. Retention ponds are one of the few effective ways to prevent flash floods or deluges. Retention ponds can also mitigate the effects of high tides, which restrict river flow into the sea.

The Selangor government needs to establish a system to regularly inspect retention ponds and refer issues to local authorities. Retention ponds need to be given due importance in controlling water surges from heavy downpours, especially now in the face of climate change.

V. THOMAS

Selangor