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Remember that viral video of Hub river bridge collapse? It’s famous again

An engineer explains why history is on repeat in Balochistan, as least structurally
Published 28 Jul, 2022 08:09am
<p>A portion of Hub River bridge was swept away this week during the monsoon rains. Photo: APP</p>

A portion of Hub River bridge was swept away this week during the monsoon rains. Photo: APP

Almost two years ago, on Sept 6, 2020, we reported the deterioration of a National Highway bridge between Sindh and Balochistan at Hub River. The video had been captured earlier by some traveler, and it went viral on social media.

So severe was the damage to the bridge that not only could we see its foundation piles (or supporting columns sunk into the ground) but the rest of the structure also showed clear signs of crumble. And since viral images are Pakistan’s cyber version of the National Accountability Bureau, the political governments were forced to respond. The panic subsided after the blame was assigned to the National Highway Authority and sufficient noise was that work was being done to gauge the damage and assure it was a durable bridge.

Then two years later, another image surfaced. Of. The. Same. Bridge.

The media may not have done justice to its paychecks reporting on Balochistan but the reality is that this year’s off-the-charts monsoon rains have ravaged the province. One spectacular visual example and, indeed, symbol of deep systemic rot, is this Hub River Road bridge. Fresh images show that it just gave in to the torrents of water and was washed away this year. Fresh footage shows that the centre spans of the bridge were swept away, and are probably now floating around somewhere in the Arabian Sea on their way to Oman.

This was going to happen. We can thank God that no one has been reported dead and if the NHA is to be believed, traffic was not affected too badly as people switched to using the bypass at Hub city as an alternate.

The question is: why did this happen? There are several explanations. One main reason for the bridge collapse seems to be the absence of proper hydraulic engineering when it was planned in the first place.

The second explanation can be found in questions surrounding regulations. For example, what load (or weight) was it designed to take? How much load could safely pass on the bridge and what was the actual load that it bore?

Satllite imagery of the Hub River Bridge
Satllite imagery of the Hub River Bridge

In Pakistan’s socio-engineering culture, project managers are fans of pouring concrete on steel rods. For every problem, they have only one solution: pour more and more concrete with steel reinforcement. Our policy makers are no better, as they hide behind Mother Nature (natural calamities) to explain their failures.

But in the case of the Hub River Bridge, there is one more reason for the collapse: uncontrolled sand mining. This was why its pillars and foundation piles were exposed. The sand (for construction) was not excavated around the bridge as such, but upstream or downstream. When you suck sand out like this sand pits form. They have hydraulic significance on the flow of water and can make it more lethal for any structure like a bridge over a river. The velocity of flow can change direction because the prism of the channel has been changed. (Prism is a technical word that describes the V shape of the ground the river flows in). When the prism of the channel changes, the river’s water can actually flush away structures.

All this engineering and talk of hydrology aside, think of the money that will have to be spent to fix the bridge. And think of how we live in an age of a certain trauma – instead of happy photos going viral, Pakistanis are constantly bombarded by images of devastation and destruction.

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Balochistan

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Balochistan flood

Hub river

monsoon 2022

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