FROM THE FIELD
Geohazards in Bangladesh

Sampling on the Ganges and Brahmaputra Rivers

by |February 4, 2017
Chris smiling broadly as he and Humayun buy 11 lbs of Jordibaja, a local Kushtia snack food from the most famous bakery that makes it.

Chris smiling broadly as he and Humayun buy 11 lbs of Jordibaja, a local Kushtia snack food from the most famous bakery that makes it.

From Khulna in the SW, we are heading to Rajshahi on the Ganges River, but first we are stopping at Kushtia, Humayun’s home town. Because the road on the more direct route is supposed to have bad road conditions, we took a longer route, way longer. It wiped out any chance to get to Rajshahi in time for some fieldwork, but it did boost my districts (states) of Bangladesh visited to 40 out of 64. After many hours on the road, we reached Kushtia and out goal – jordibaja, a fried noodle snack that is only available here. Chris bought 10 500 gram bags, about 11 lbs, at the bakery that makes

Liz in Rajshahi walking back to our group protected by two policewoman that were part of our escort during a quick visit back to our van.

Liz in Rajshahi walking back to our group protected by two policewoman that were part of our escort during a quick visit back to our van.

the best, of course. We then had a late lunch and continued to Rajshahi where we were once again joined by a police escort. Different teams stayed with us until we left the area. After finding our hotel, we all had our first hot water shower since we left Dhaka. Living on boats is great, except for the complete lack of hot water. Once cleaned up, we went to Humayun’s sister for a delicious dinner. After dinner, the commissioner of police, a former student of Humayun’s stopped by. He suggested we visit some of the chars (sandy river islands) close to Rajshahi rather than the places we went

Our police escort watches Chris and Dan measuring spectra on a char (sandy river island) to compare with satellite measurements.

Our police escort watches Chris and Dan measuring spectra on a char (sandy river island) to compare with satellite measurements.

to other years, an hour or more drive away. Chris and Dan checked their satellite images and found that the nearby chars would work, probably saving 2-3 hrs of driving.

The next morning, we headed off with out new escort, that included two policewoman. However, that had to switch off when we crossed from one precinct to another. Renting a country boat we crossed the Ganges to the chars. While Dan and Chris (with Humayun) made salinity, moisture and spectroscopic measurements, Liz and I

Dan measures the water content of a small area of quicksand we found while Liz is being sucked in as she explores it.

Dan measures the water content of a small area of quicksand we found while Liz is being sucked in as she explores it.

scouted for the proper sediment samples for her OSL needs. After wandering about the island we found what she wanted and collected a sample. Until now, her studies of the delta did not have any samples from the Ganges itself. For Dan and Chris to get the observations they wanted, we visited several chars before ending up back at the first one for them to study the transition from sandy sediments to rice fields. As soon as the chars have deposits of the right kind of sediments, people start planting crops. If the char continues

Digging out our OSL dating sample of silt on the Ganges. The tape wrapped PVC pipe had been hammered entirely into the outcrop. The sample inside must not be exposed to light or it will be ruined.

Digging out our OSL dating sample of silt on the Ganges. The tape wrapped PVC pipe had been hammered entirely into the outcrop. The sample inside must not be exposed to light or it will be ruined.

to grow and stabilize, they will move there as well. They are great places to live 9 months of the year, but a struggle during the high water of the monsoon season. The islands with migrate, eroding from one side while sediment deposits on the other. The char people have to move frequently as the chars move out from under their homes. Liz and I wandered off and found another place to sample. Now she have both a sand and a silt samples from the Ganges. It only took a few hours to accomplish the more specific tasks of this field program. When we first started visiting chars 12 years ago, we explored then from the morning

Chris and Dan discussing notes on locations to visit based on recent satellite images and entering them into the GPS.

Chris and Dan discussing notes on locations to visit based on recent satellite images and entering them into the GPS.

until dusk. We needed to see and explore all aspects of this new environment for us. Now, we are building on our work with much more focused activities.

Off the river by early afternoon, we drove across country to Bogra near the Jamuna River, as this part of the Brahmaputra is known. We were able to arrive around sunset, avoiding the sometimes frightening driving in the dark. For old times sake, we skipped the new hotel that was booked and stayed at the colorful Parjartan Hotel that we first used

Chris, Dan, and Bulbul, our driver, walking down the embankment at Sirajganj. During the summer, the water level will reach the top of the embankment as the river flow increases by a factor of 10 or more.

Chris, Dan, and Bulbul, our driver, walking down the embankment at Sirajganj. During the summer, the water level will reach the top of the embankment as the river flow increases by a factor of 10 or more.

in 2005. It is literally painted the colors of the rainbow, as well as having more character, even if everything is not quite working. This was the hotel where my room once had electric outlets of 4 different shapes, requiring every adapter I had to recharge my equipment. Now I always bring an outlet strip so I only need one adapter.

We had planned to go north to Gaibandha, but a new satellite overpass showed that we could get all the data we needed farther south at Sirajganj. We could cut out a day. As it turns out, this was fortuitious. I have a family

Humayun walks to the country boat we rented at Sirajganj to bring us across the river to the chars.

Humayun walks to the country boat we rented at Sirajganj to bring us across the river to the chars.

emergency and have to return to the U.S. From Sirajganj we could return to Dhaka, rather than stay at Tangail. Chris and the others can do the rest of the field work as day trips from Dhaka. It is more driving for them, but will enable be to catch the evening flight back to the U.S. We packed up and headed to the embankment at Sirajganj, which protects the city from the shifts in the Jamuna River. We walked down the embankment (the river level is about 7 m or 23 feet higher during the summer monsoon season). We headed for a large char that

Liz examines an outcrop on the large char across from Sirajganj while looking for appropriate sediments to sample. Wherever the conditions are right, the chars are planted with crops while the bare sand remains exposed in the younger parts of the char.

Liz examines an outcrop on the large char across from Sirajganj while looking for appropriate sediments to sample. Wherever the conditions are right, the chars are planted with crops while the bare sand remains exposed in the younger parts of the char.

we first visited in 2005. It has grown and become attached to other chars. It also has much more agriculture, they are growing rice, peanuts, lentils, corn and more. The complex history of changes in the char provides lots of different sediment types for Chris and Dan and plent of cut bank surfaces for Liz to get a good silt sample. A few hours of exploring, sampling, measuring and we were done. Since it is Friday, the Muslim holy day and the weekend here, traffic is light until we reach Dhaka. Near the university and our hotel, the streets are packed with people and rickshaws. Still we manage to get to the university to drop off equipment and for me to get 7

Liz measures the position of the hammered in sampling tube before we dig out and collect our last sample, a silt from the Jamuna (Brahmaputra) River.

Liz measures the position of the hammered in sampling tube before we dig out and collect our last sample, a silt from the Jamuna (Brahmaputra) River.

GPS receivers that finally have to be returned to UNAVCO after 10 years. This is the last of the 11 we were lent in 2007 by them. They provide geodetic data and services for NSF and allowed us multiple extensions that enabled us to get this much needed data for so long. It is the basis for our paper on the potential earthquake hazard in Bangladesh as we can see the slow motion of the surface (0-17 mm/y) that indicates the buildup of strain in the earth. Then back to our hotel to meet Dhiman and have a final dinner together before an Uber takes me to the airport. I am leaving to return

A local farmer shows Liz the peanuts he is growing on the char (behind them). Peanuts and lentils are common winter, or rabi, crops on the higher, drier parts of the char. The freshest peanuts we ever ate.

A local farmer shows Liz the peanuts he is growing on the char (behind them). Peanuts and lentils are common winter, or rabi, crops on the higher, drier parts of the char. The freshest peanuts we ever ate.

home, while they will carry on without me a few more days. They will visit the confluence of the Ganges and Brahmaputra Rivers, and the Padma, as the combined river is called. For me, my main goals for this trip were accomplished.

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