Weak flood defences 'risking lives'

Recent flood events in Nepal, India and Bangladesh that displaced millions have stoked fears that defences along rivers in the region may not withstand climate change-induced floods, and could result in bigger catastrophes.

Experts say many infrastructures are becoming weaker while the rivers' flows are getting stronger - a classic setting for projected climate change calamities.

Most floods this year were monsoon-related and many would argue they had nothing to do with changes in the climate.

However, the Kosi disaster in eastern Nepal that left millions of Nepalese and Indians homeless was a different story altogether. The devastation was the result of human mistakes.

The embankment along the Kosi was not properly maintained, resulting in it being overrun by the meandering river even when there was no flood.

The event has forced experts to imagine what could happen if rivers like the Kosi swell as the projected impacts of climate change take hold.

"It is entirely possible that some of the existing structures could prove inadequate and possibly dangerous," said Rajendra Pachauri, head of the Intergovernmental Panel on Climate Change (IPCC).

"They might not be able to withstand higher frequency and intensity of floods in the region," he told the BBC.

Weakest link

It isn't just Kosi that has exposed the structures' vulnerability.

Crumbling embankments are being washed away by floodwater

The recent monsoon season, which ended last month, also washed away some weaker spots of the defences along other rivers in the region.

Indian media reported that water from the Bramhaputra breached embankments at many key sites in Assam state.

In neighbouring Bangladesh, the Jamuna River also burst through embankments.

"In Jamuna, the disaster was Kosi-like," said Ainun Nishat, a water resources engineering professor in the IUCN Bangladesh office.

"Just like in Kosi, the embankment of Jamuna has become weak as many of its sections are still built using sand, so it failed to withstand the pressure and there was flooding."

In western Nepal, smaller rivers - tributaries to Ganga - wreaked havoc, displacing tens of thousands as well as damaging embankments, culverts, and even highways.

By the time these swollen rivers merged into big rivers such as India's Ganga, the scale of the disaster had multiplied.

In Uttar Pradesh state, for instance, nearly three million people in 5,000 districts had been affected.

Relief officials said 7,000 houses in the state had collapsed and 350,000 had been partially damaged.

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