Debris slide at Kampung Sg. Chinchin, Gombak, Selangor

Abstract

On 21st September 2001, at about 6.00 pm, a landslide occurred on the hill slopes of Bukit Guling Ayam at Sg. Chinchin at the 8th milestone of Jalan Gombak. In this incident, two houses were damaged and one person was killed. Investigations carried out showed that the quartz reef along the top of the ridge at Bukit Guling Ayam intrudes into granite. The foot slopes of the hill are generally gentle to moderately steep, varying from 0° to 25°. The mid slopes are more steep with a gradient of 25° to 35° and towards the upper reaches of the slopes, the gradient is about 35° to 45°. The hill slopes are generally composed of colluvium with abundant boulders. The landslide scar measured about 15 m wide near the crown and the sides of the scar had slumped about 1 to 1.5-m. Scouring by the slide debris which was estimated to be 4,000 cu metres in volume had left behind a scar of about 120 m long. The landslide was triggered off by the heavy rainfall which had occurred a few hours earlier. The hillslopes in the vicinity of the landslide are potentially unstable as they are generally steep with gradients more than 30° and are underlain by colluvium. There are also some loose rock blocks in the quartz reef along the ridge which pose potential rockfall dangers.