The Omchhu Bridge which was inaugurated and opened for traffic earlier this year is so far safe despite water level reaching its deck level. The rise in water level thus touching the deck had raised concern among the people who feared the bridge would be damaged.
However, though the sedimentation of debris caused by continuous rainfall has caused the river bed to rise causing the water to reach the deck, Thromde officials have clarified that there is minimal risk of damage to the bridge.
Earlier, the Amochhu River which flows near the riverused to wash away whatever debris Omchhu brought but now as the Amochhu has been diverted to the right, debris settles near the new bridge due to the slow river current in the plain.
The new bridge is 194.5m tall-the highest flood level from the river bed, which means the river would not reach the deck irrespective of the volume of water even during peak monsoon. It is assumed that the river at the highest would reach up to 2.5m. Moreover, the bridge has two meters vertical clearance which adds space for the river to flow through the bridge. But this year, the sedimentation below the bridge stopped the smooth flow of water through the bridge, said a Thromde official.
The river has also washed away the staging formworks of new curvilinear bridge which is being constructed. The debris are washed away and deposited below the Omchhu bridge.
With multiple tributaries and surface run off, Omchhu has swollen with the recent continuous rainfall.
The bridge has also been designed based on scouring to preventflooding. The bridge has an eight meter deep foundation which has become stronger with the sedimentation.
The bridge was earlier designed with pier foundation which failed during test. Later, the bridge was newly designed after consulting with the experts. The bridge design had three piers which could have blocked the debris to flow down. “We did away with the old design after consultation with the works and human settlement ministry and the consultants,” said the Thromde official.
Since Thursday, the Thromde has deployed excavators from a private contractor to clear the debris to prevent river overflowing the bridge
It is assured that the bridge and its foundations are intact and safe. If the rainfall continues, the Thromde feels that the river may overflow and girder could shift. But the girder is also secured with seismic arrester which will keep the bridge intact and prevent damage. “There is no chance of the bridge to collapse,” said the Thromde official.
Krishna Ghalley from Phuentsholing