geohazards_main FROM THE FIELD
Geohazards in Bangladesh

Working in the Bangladeshi Countryside

by |March 20, 2015
Sailing through the Sundarban Mangrove Forest

Sailing through the Sundarban Mangrove Forest

The shortest route to where we are headed has silted up and is no longer passable. Farmers have moved in and started shrimp farming there. As a result, we and others have to take a longer route through the Sundarbans Mangrove Forest. Our first tantalizing sight of the forest we will return to later. Will lots of ship traffic on this route, the inevitable happened. Last December a ship collision resulted in an oil spill. With initial inaction by the government not wanting to face it, the local people went in and cleaned up the oil themselves by hand. Without any protective gear from the toxic oil, they saved the situation. Now only a slight oily film is visible at low tide. We started at 2 am to travel through the passage with the rising tide.

The team studying agriculture changes in Bangladesh meet with Chris Small to plan for interviewing farmers

The team studying agriculture changes in Bangladesh meet with Chris Small to plan for interviewing farmers

By 10 am we had passed through the Sundarbans to the Pusur River and stopped to pick up Carol Wilson and Saddam Hosain. They will join us for a few days from another boat that a Vanderbilt-Dhaka University team is using for research work at Polder 32. We continued up to Khulna ghat (dock). We had lunch and transferred to land by launch. In three vans we drove for and hour to asite where we installed instruments to measure the compaction and subsidence of the sediments. In 2011 we drilled 6 wells with depths from 20 to 300 meters installed optical fiber strainmeters. The fibers are stretched like a rubber band and every week one of the sons from the Islam family uses a device to measure its length, watching to see the change as the sediments compact.

Tanner and Yassamin in a discussion at sunset.

Tanzir and Yassamin in a discussion at sunset.

While I service the equipment, my students spread out in several groups. Four of my students, each with a Bangladeshi partner spread out over the area with Chris Small to interview farmers about their farming practices, what crops they grow and changes through time. The information the agriculture team collects will help calibrate remote sensing observations. The other 6 students work with Kazi Matin Ahmed of Dhaka University form 5 teams to measure arsenic levels in the wells that provide drinking water. Finally, Liz Chamberlain and Carol use an augur to drill into the sediments. They will look at the stratigraphy and collect a sample for dating. The river that flows through the area used to me 300 meters (1000 ft) wide, now it is only a few meters. The silting in banks have been occupied by squatters using the new land for shrimp farming. The Islam family moved here in 2002.

Fisherman on the Pusur River using the incoming tide to sweep fish into their nets

Fisherman on the Pusur River using the incoming tide to sweep fish into their nets

When we arrive, it is hard to recognize the site. The government is excavating the river, widening it so boats can use it again. There are large piles of mud everywhere. Finally we find the right place and are relieved to find that they went around our instruments. In the afternoon, I met the engineer doing the work and he reassured us that our instruments will be untouched. Only time will tell if the measurements will be affected.

I was the least successful of the groups. We collected the data from the 6 compaction meters and surveyed between the GPS and wells to look at changes in the surface elevation. However, the cap of the well collecting water level data was rusted shut. When we really tugged on it, the pipe started to bend. We will have to return with WD-40.

We arrived to find that 2 weeks earlier excavations had started to widen the river. It has shrunk from 300 to 3 meters wide.  Gratefully, they left our instruments intact.

We arrived to find that 2 weeks earlier excavations had started to widen the river. It has shrunk from 300 to 3 meters wide. Gratefully, they left our instruments intact.

Even worse the GPS was dead. Some problem with the solar panel system, but with the tool kit back in the states, I couldn’t diagnose it. I will take the receiver back to Dhaka to download the data, but Humayun will have to come to repair the power system. At least the students had a more successful time talking to farmers and measuring arsenic. It was their first time talking to rural Bangladeshis and spending time in the countryside. They thoroughly enjoyed it.

Collecting a water sample for testing arsenic levels at the well of the Islam family, host of the compaction meter.  It came out clean.

Collecting a water sample for testing arsenic levels at the well of the Islam family, host of the compaction meter. It came out clean.

Liz augurs through the sediments on the riverbank  to get a sample for OSL dating, attracting a crowd

Liz augers through the sediments on the riverbank to get a sample for OSL dating, attracting a crowd


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