In Silt, Bangladesh Sees Potential Shield Against Sea Level Rise

The rivers that course down from the Himalayas and into this crowded delta bring an annual tide of gift and curse. They flood low-lying paddies for several months, sometimes years, at a time. And they ferry mountains of silt and sand from far away upstream.

Most of that sediment washes out into the roiling Bay of Bengal. But an accidental discovery by desperate delta folk here may hold clues to how Bangladesh, one of the world’s most vulnerable countries to climate change, could harness some of that dark, rich Himalayan muck to protect itself against sea level rise.

Instead of allowing the silt to settle where it wants, Bangladesh has begun to channel it to where it is needed — to fill in shallow soup bowls of land prone to flooding, or to create new land off its long, exposed coast.

The efforts have been limited to small experimental patches, not uniformly promising, and there is still ample concern that a swelling sea could one day soon swallow parts of Bangladesh. But the emerging evidence suggests that a nation that many see as indefensible to the ravages of human-induced climate change could literally raise itself up and save its people — and do so cheaply and simply, using what the mountains and tides bring.

“You can do a lot with the silt that these rivers bring,” said Bea M. ten Tusscher, the Dutch ambassador to Bangladesh. The Netherlands, itself accustomed to engineering its vulnerable low-lands, helps Bangladesh with water management projects. “Those are like little diamonds,” Ms. ten Tusscher said. “You have to use it.”

Satellite images show that in the natural process of erosion and accretion — in some places speeded up by a series of man-made dams and channels — Bangladesh has actually gained land over the last 35 years.

Skeptics say it is folly to expect silt accretion to save the country. Accretion happens slowly, over centuries, they argue, while human-induced climate change is hurtling fast toward Bangladesh. The new land is too muddy and slushy for people to safely live on, and the force of the Himalayan rivers is so powerful that it can wash away newly gained land in one fluke season.

“If you have time to wait, it will happen,” said Atiq Rahman of the Bangladesh Center for Advanced Studies. His country, he added, does not have time to wait.

The silt-trapping experiment has yielded tentative but visible gains here in Beel Bhaina, a low-lying 600-acre soup bowl of land on the banks of the Hari River, a tributary of the Ganges, about 55 miles upstream from the Bay of Bengal. Even at this distance from the coast, it is among the country’s most susceptible to sea rise. The river swells each day with the tides. Creeping salinity in the water table is a harbinger of future danger.

Here, misery made way for a discovery. A devastating flood 10 years ago left this soup bowl — a “beel” in Bengali — inundated with water that reached above Abdul Lateef’s head. No paddy could grow, recalled Mr. Lateef, now 56. Houses went under. The river was so heavily silted it hardly moved. Many families were reduced to penury.

One night, desperate to drain the water, Mr. Lateef and his neighbors punched a hole through the mud embankment that encircled the soup bowl. They watched as the water rushed out. Then the high tide began to haul in sediment, and the soup bowl swiftly filled with silt.

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