'Overflowing water from dam made it worse'
Published on: Thursday, October 09, 2014
PENAMPANG:
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The overflowing water from the Babagon Dam was an additional cause of the very rapid rise in the flood level in Penampang on Tuesday.A member of the Institution of Engineers Sabah Branch, who was invited to the site, said it was like opening the gate of a reservoir.
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"However, there is no gate that can be opened by the operators as it is under construction.The overflow is a vertical drop like a waterfall which pushed the upper Moyog River to flow faster than normal," said the retired Civil Engineer from Kg Hubah.He said this Wednesday after observing the abnormal flood pattern that occurred in Penampang from Monday (Oct 6) to Wednesday (Oct 8) morning, which also badly flooded Donggongon town.
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The first time the flood from Moyog River reached Donggongon was during the tropical storm "Hilda" in January 1999.The retired engineer also opined that it would have been better if there was a small gate from the dam that can be opened earlier to release a small discharge so that the partially emptied reservoir can capture the intense rainfall afterwards. "However, when the reservoir is already full and the intense thunderstorm falls over the large surface of the reservoir, this is no different from the rain falling over the roofs and solid concrete pavement in town," he said."Hydrologists call this 100 per cent surface run-off and all of this volume simply falls over the vertical overflow concrete structure of the dam," he added."In comparison, any intense rain falling over the Babagon catchment area before the dam was built would have been slowed down by the sponge effect of the trees, vegetation and the rivulets. I challenge any hydrology professor to prove me wrong," he said.The flood this time was also extremely muddy and this must be contributed by the large bulldozing of land for agriculture at the Moyog catchment which the District Officer was reported earlier to have given a stop-work order."With these extreme changes in the rainfall at the catchment of Moyog, the only mitigation is better drainage system downstream but instead even natural rivulets have disappeared due to haphazard development and when complaints are submitted, we are met with denials from those in authority," he claimed.As a proof of downstream effects, the width of the river at Dambai Bridge is partially constricted due to temporary earthworks for construction access as shown in pictures taken just before the flood, he added. The flood warning siren was heard at Penampang Proper village around 9pm on Monday (Oct 6), where the usual action by the residents were to move their cars to the higher ground of the road near the bridge. "At 6.30am Tuesday, a very intense rain was observed for one hour. After the rain had stopped, the flood water suddenly rose about one foot in 10 minutes starting from 9.50am and continued to peak at 1pm, which is coincidental to SMS from contacts at Babagon that the overflow of the dam had stopped at 12.30pm. Stay up-to-date by following Daily Express’s Telegram channel.
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