Geohazards in Bangladesh
Earthquakes, floods, sea-level rise and sudden shifts in river courses threaten many of the 150 million Bangladeshis living in the low-lying Brahmaputra River delta. Scientists from Lamont-Doherty, Dhaka University and other institutions have begun a five-year project to understand the hazards and the possible hidden links among them. Lamont seismologist Michael Steckler keeps us up to date on the work.
We had a smooth trip to Kolkata with our two taxis amazingly staying together through the traffic. After checking in and freshing up, we went out for dinner and found a great Bengali Restaurant filled mostly with Bangladeshis around the corner. Our hotel turned out to be next to an area where Bangladeshis frequently stay, including Humayun previously. In the morning, he and I went for an early morning walk through the park and saw the Queen Victoria Memorial. Circling back past all the cricket players, we passed Fort William, the original British fort here, and joined Doug and Diane for breakfast. Our car arrived and before heading to the Sundarbans, we drove around to get shots of the Hooghly River. Before the 1600s, this was the main course of the Ganges, but since
then it shifted to it present course into Bangladesh. We got some shots from the new bridge before being chased off. Then we headed to the Strand to get close to the river. While we were filming, a funeral procession arrived to scatter ashes of the deceased into the river. Once the Holy Ganges, always the Holy Ganges. We couldn’t have planned it better.
Then, off to the Sundarbans. Where we were going was a lot farther than implied. This is because of a difference in naming. In Bangladesh, the Sundarbans is the National Mangrove Forest. The cultivated areas that previously were forest are not considered the Sundarbans. In India, they are. Thus we entered the Sundarbans after 2.5 hrs, but still had that long to go to meet our boat.
Admittedly, some of the cultivated areas in India still maintain mangroves outside of the embankments, which is not the case in Bangladesh. Continuing on, we reached literally the end of the road and carried our luggage (including a 50 lb. bag of rock samples) down to a ferry that took us to Gosaba. There, we first got a hand rickshaw to get the luggage across the town, then got two motorized rickshaw trucks to cross to the other side of the island. Finally, we were met by a boat that took us across the river to the eco-lodge where we would stay. After a late (4 pm) lunch we went on a sunset boat ride through some tidal channels. The saw and heard lots of bird and at times the channel became so narrow that we had to push branches away to fit through. The
trees here overhang the channels more than in Bangladesh. We would see further differences tomorrow. After finally showering off, we met other people staying at the eco-lodge, started by 4 cousins including Ajoy, who is leading our trip. The lodge is solar powered, so electricity is limited,but the water was refreshingly cool, not cold. We all heard a performance of Bengali Baul music, recognizing some songs from similar experiences across the border. After dinner, we all went for some local rice wine and then a boat ride to see bioluminescent plankton in a small channel. If you wave your hand in the water dots of light flash.
In the morning, we started at 6 am to have enough time before I had to head for the airport. We picked
up food and a cook and permits and a guide and finally were ready to enter the forest. In India, no one is allowed off the boat to step on the forest, nor to stay overnight in the forest, even on a boat. Thus many hotels and lodges have sprung up outside the forest for tourists. Many come simply to party and drink. We are very glad to be using an eco-lodge that is more respectful of the land and the local population.
At 8, we finally entered the national forest. Among the differences from the Bangladesh side we noted were the shorter height of the trees in the more saline water, the lack of sediment in the water, and the extent of bank erosion. Where the eastern Sundarbans is fresher with ample sediment carried by the tides due to its proximity to the Ganges-
Brahmaputra-Meghna River mouth, the western, Indian Sundarbans is more saline and lacks new sediment. Between subsidence and sea level, it is loosing ground. More land is being lost than gained. With the higher salinity, there is also less wildlife. However, there was a tiger sighting this morning. We sailed to the spot, but it was too late, we missed it. Still, we spent 4 hours sailing through tidal channels of different size, eating, and filming. Doug captured the beauty of the Sundarbans and I was interviewed with a great backdrop.
After completing our work, we briefly visited an observation post, we took a short cut through an interior channel in Gosaba Island, dropped off our guide, and crossed the channel to our car. Three hours later, I arrived here at the airport to start my journey home. It was an intense, yet calm 48 hours in West Bengal, the third leg of three very different pieces of this trip.
Humayun Akhter, my main collaborator in Bangladesh, joined me at the airport and we flew together to Kolkata. We spent the night at a nondescript hotel near the airport. The next morning, we met up with film makers Doug Prose and Diane LaMacchia in the airport and all flew together to Aizawl, the capital of Mizoram state in NE India. Doug and Diane have funding from NSF to expand the 5-min YouTube video they made about our project two years ago (https://www.youtube.com/watch?v=WTETuqJPygs) to a ½ hour TV special. Their previous films have been shown on PBS.
The Sumatra subduction zone, source of the 2004 earthquake and tsunami, continues to the north where it encounters the Ganges-Brahmaputra Delta. The 15-20 kilometer thick delta sediments are folded and faulted as they enter the subduction zone. Because of the huge amounts of sediments, this is the only subduction zone whose front is subaerial – entirely exposed on land. In Bangladesh we can see the beginning of this process. Here in Mizoram, farther east, the former delta sediments are folded up into a very hilly terrain. The steep slopes are subject to frequent landslides. One that started last October has moved again and blocks the main road from the airport to the city of Aizawl. As a result, we had to take a longer, slower, bumpier and dustier road to get to the city.
We met up with Nano Seeber and Paul Betka from Lamont at breakfast. They have been doing geologic mapping the region and returned to Aizawl late the night before. We spent the day circling the city and visiting outcrops, many ones I had seen my last time here. We had several interesting discussions on differences of interpretation of the strata. I had visited most of these outcrops before, but it was the first time for Humayun. At the end of the day we were joined by
Vineet Gahalaut from the mainland, as the rest of India is considered here. The people here look Asian and the Mizo language is a tonal language in the Tibeto-Burmese family. Plus, almost all Mizo are Christian. Mizoram is part of India, but also distinct, like many of the other states in NE India. Part of the sense of separation is that the 7 NE states are only connected to the rest of India by the narrow 23 km (14 mi.) Siliguri Corridor between Bangladesh and Nepal – the chicken neck. We spent the evening talking with Vineet about future joint projects in this region.
The next day we were joined by Victor Ralte, our partner from Mizoram University, who became a proud father of a fourth daughter last week. We all headed north, visiting geological sites and filming
beautiful vistas, dropping Vineet off at the airport and continuing on to Kolasib, a small town about 70 km north as the crow flies, but probably twice that on the windy roads of Mizoram. We stayed in Hotel Cloud 9. I had been told since I was a child that I was always off on Cloud 9 and now I was actually here. However, the electricity wasn’t for the first few hours, so showers were cold, but the dinner was hot.
The next day we headed still farther north to see some complex faulting associated with the growth of the anticlines – the hills of folded strata. As we examined each outcrop, it was also clear that we were passing through several kilometers of rocks in which the environment that were deposited in shallowed from the inner continental shelf (10s of
meters water depth) to the tidal zone to estuaries like the present Sundarbans to fully fluvial (river). This represents the ancient Brahmaputra Delta passing across this area as it grew southwards. That several kilometers of sediments were deposited while the environment only shallowed by 10s of meters indicates that there was a lot of subsidence to make space for the sediments. I will have to model this when I return.
Stopping for a beautiful sunset over the hills, we finished heading back to Aizawl for a last dinner together. In my room as it turned out since the restaurant closed for some repairs. The six of us ate a mixture of American, Indian, Chinese and Mizo food with plates dishes and ourselves filling all available surfaces. Today, a quick stop at Mizoram University and then back to Kolkata for my last leg before home.
For our last morning, we did a dawn silent boat ride up a tidal channel. Since the students did one the day before, a few sat out. The ones that remained stayed silent to increase our chance of sighting animals. We saw many birds: kingfishers, kites, egrets and others. There were numerous mud skippers – fish that come out of the water to avoid predators – and a wild boar. The highlight was sets of fresh tiger tracks. The first set came down one bank and up the other. Tanjil, our guide, estimated that they were 5-6 hours old. After returning to the ship, we headed north through the Sundarbans towards Dhaka, a day and a half journey.
Along the way, we had a quick stop at a small village along the Baleshwari River. Chris Small had noticed that the width of the villages in this area had doubled between 1989 and 2010. We wanted to find out why. A small party went ashore to talk to the villagers. Unlike Polder 32, the water here is fresh and it shows. Lots of trees and a more prosperous and happier population. Boys jumping
into the creek from the top of the sluice gate. The trees included betel nut, papaya and other fruit trees and well as trees for wood. The local policy is that for every tree they cut down, they plan 4 new ones. This accounts for the increased size of the villages, a net switch from rice field to trees. After only a ½ hour, we had to return to the boat, drop off Carol and Saddam where a car would take them back to Khulna, and continue on our way.
We decided not to stop for visiting Barisal or swimming and thus were able to get to Dhaka the next afternoon rather than at night. Instead of spending the night on the Kokilmoni on the polluted, smelly, Shitalakshya River, we went into Dhaka and back to the Ambala Inn. More importantly for the students, we arrived with time to
shop. After checking in, we formed groups of 2 US and 1 Bangladeshi and sent them off by foot and rickshaw to New Market for shopping. The lack of shopping opportunities was the main complaint about the trip. They made up for it with clothes for themselves and presents for friends and family. That accomplished, we gathered for a final dinner in Bangladesh at Voot, one of our favorite restaurants. The slow service with cooking for 22 allowed plenty of time for socializing and picture taking. The students showed off their new Bangladeshi togs and a good time was had by all.
The next morning was our chance to see Dhaka. We met our counterparts the university and headed to Old Dhaka. We stopped at the 800-year old Dhaleshwari Temple where a child was getting
her first solid food in a Hindu ceremony. Then on to the Lalbag Fort built by the Mughals in 1676, or so we thought. Sunday is its day to be closed. We decided to go to the Ahsan Manzil, known as the Pink Palace. As we drove through the narrow streets, traffic got slower and slower. Finally, we stopped and decided to walk the last quarter mile. Now we all got a true taste of Old Dhaka, dodging rickshaws, hand trucks, pedestrians, and workers balancing parcels on their head. We managed to get all of us there and toured the grounds overlooking the Buriganga River then the massive palace built by the Nawab of Dhaka in 1872.
After the chaotic walk back to the vehicles, we spent an hour going the few kilometers back to Dhaka University. When we finally got back, we
had to abandon our plans for visiting the National Museum. We went to lunch at a very Bangladesh restaurant, picked up our luggage at our hotel and headed to Aarong. It is an upscale shop that sells all Bangladeshi clothes, crafts and products. The students got their last fill of shopping. Satisfied with their gifts, we headed to the airport. They went home, while I started my next leg in Kolkata and Aizawl, India.
We left Hiron Point with the high tide and sailed through small channels of the Sundarbans Mangrove Forest. As a tidal marsh, the Sundarbans is crisscrossed by channels with sizes that range from 10 km across to less than a foot. The tides rise and fall periodically inundating all of the land. Mangroves are trees that are adapted to living in brackish water. Different tree species are found in different parts of the Sundarbans, adapted to different levels of saltiness.
We arrived at Kotka in the afternoon. Most of the group went on a forest walk with Tanzeel, our guide. A smaller group of us split off to visit thee remains of 300-year old salt kilns. We passed Chital deer and a wild boar on the way. A stag was silhouetted at the coast before it ran off. The
people that built the kilns used to allow seawater to flow into evaporation pans at Spring high tide. Before the next Spring tide they would bake the concentrated brine in clay pots to produce salt. The kilns are surrounded by innumerable potsherds, and quite a few intact clay pots. It is thought that the operation was suddenly destroyed, abandoned and buried, perhaps by a 1699 cyclone that killed 50,000 people. Recent erosion, include the destruction by Cyclone Sidr in 2007 have unearthed them.
Since the age of the kilns is known, it is a good site for Liz to use OSL dating to determine the sedimentation rate. We drilled several auger hole to determine the stratigraphy, the deepest one was 5.8 meters. Liz drilled assisted by two crew from
the Kokilmoni while I took notes and photos. The kiln site is now in the intertidal zone – exposed at low tide and covered at high tide. This means that they have subsided since they were last used. The rate is estimated as 4.1 mm/yr by a German group that worked here. We completed 3 holes, but ran out of daylight before we could take the OSL samples. We returned to the ship, walking past buildings destroyed by Sidr with our larger group who ended their forest walk at the kiln site.
We returned at dawn the next morning – with a guard to protect against tigers – while the remainder of the group went on a silent ride up a tidal creek. We collected 3 OSL samples from different depths, the last one completed as the rising tide reached over our knees. Whenever the
sampler was removed from the hole, one of us had to keep our hand in the hole, usually Matt, so we could find it again. Happy with our successful sampling, we returned to the ship for breakfast.
Back with the others, we set out for a forest walk to Kotka Beach. Climbing an observation tower, we got an overview of the region. There are old shoreline deposits here that are above the high water level. These sediments provide evidence of the seaward progradation of delta. As a result there is a meadow and many non-mangrove species as the area doesn’t regularly flood. This attracts a lot of deer and, as a result, tigers. However, we only deer. We also walked through the muddy mangrove forest and finally emerged at Kotka Beach where we went swimming in the Bay
of Bengal. We continued along the beach for a few kilometers passing hordes of scurrying crabs. Finally, we rejoined the Kokilmoni for a late lunch.
In this area, plans always have to be adjusted according to the tides and weather. As a result, we switched our visit to Bird and Egg Islands to later in the afternoon instead of the following morning. These two islands emerged from the sea about 20-25 years ago and have grown and merged. In answer to the age old question, the Egg came first. While a few people skipped the walk after the morning’s trek, most of us went along. It is a great place to see the biological succession that develops on a new island. The coast is bare sand with the high water mark littered with plant debris. Beyond the wind-blown coastal dunes, grasses
have taken hold. Then tall grasses and a scattering of shrubs and then trees in a muddy salt marsh. Finally in the distance is a full-fledged mangrove forest. We saw tracks and spoor of deer and monkeys, but as of yet there are no tigers on the island.
An unsuspected bonus was a tidal channel near the beach. Here at small scale, we could see all the features of river systems that we discussed in class: cut banks and point bars, meanders and avulsions, small deltas and chars. All at a scale that brought the geology to life for the students far better than any lecture or photos. It was a long and very successful day in the Sundarbans.
We sailed downstream to join the M/V Bawali with the Vanderbilt-Dhaka-Khulna group working on Bangladesh late at night and awoke to greet old friend and meet new ones. After breakfast, we all headed to Polder 32. Polder 32 is one of the islands that had embankments constructed around them to prevent flooding and improve agriculture. They use the Dutch term polder for the embankments. Polder 32 was one in which the polders failed during Cyclone Aila in 2009. As it turned out, while the polders improved agriculture as planned, it also led to subsidence of the island. It is now over 4 feet lower than land outside the island. This led to widespread flooding of the island after the cyclone that lasted for almost 2 years. We have been studying the causes and impact for the last few years. The subsidence inside the polders put everyone at risk as an unintended consequence of keeping out the natural flooding and sedimentation to improve agriculture. How to manage this system now is a difficult problem.
We also learned about the water problems at Polder 32. The groundwater is saline and not usable for either drinking or irrigation. They can only grow one crop a year, so the fields are all fallow except for some vegetable gardens by the homes. In other parts of Bangladesh 2 and even 3 crops a year are possible. We saw the abandoned tube wells installed by a wealthy donor after Cyclone Aila. They are all saline. Kazi Matin showed us his MAR site – managed aquifer recharge. They are attempting to create a pool of fresh groundwater over the heavier salt water providing a source of sweet water. Nearby, the Vanderbilt team is
installing equipment to measure water levels and flow at different depths, trying to better understand the groundwater system.
While the students fanned out to discuss agriculture with the farmers and test what few tube wells they could find, a small group of us took a speed boat to a large industrial shrimp farm on Polder 33. We found the site to be surrounded by a barbed wire fence. We found out later that it is to protect the site from tigers as it is on a peninsula surrounded on 3 sides by the Sundarbans. There was a rumor that the shrimp farm had closed and could be used to calibrate remote sensing data, but it was fully running. They grow 2 crops of jumbo shrimp a year over 9 months and spend the
remaining 3 months cleaning the ponds and preparing for the next season’s crop. They were one of the first large-scale shrimp operations in Bangladesh.
We sped back to the ship to find that the others had all returned and were having a swim break. I barely managed to change into my swimsuit and jump in before we all had to return to the ship to sail to Hiron Point. The strong tides in southern Bangladesh set our schedule as we try to catch tides going our way and avoid sailing against the tide. We sailed down channel between Polder 32 and the Sundarbans to the Shibsa River. At the end we passed Kalibogi. It is a peninsula at the end of Polder 32 that has had about a kilometer of erosion. It is now very narrow and the
embankment has been moved north of the peninsula, abandoning it. The shrimp farms that were once here are gone. There are only homes poorly protected from the elements and fishing is their only livelihood.
We sailed down the Shibsa to the Pusur River and overnighted in a narrow channel across from Hiron Point. In the morning we crossed. This stop is manly for me to service our GPS installation. We are using the precise measurements to determine the subsidence rate of this part of the delta. There is a tide gauge here that monitors the relative level between the sea and the land. While intended for navigation, over time it records the combined effect of land subsidence and sea level rise. With the GPS, we will be able to separate the two rates.
We all took the small wooden launch into the channel to the Forest Station. The Kokilmoni stayed outside lest it get trapped behind the mouth bar when the tide goes out. Hasnat and I, with Sabrina filming went to service the GPS while Liz demonstrated how to auger to get stratigraphy and sample for OSL dating. Small groups also took turns going up the observation tower. I discovered that I did not have my internet adapter – Apple have eliminated them from the newest Mac. I was stuck. Hasnat rushed back to the ship with the launch to get his computer. I could only wander around. I was shown the small spring with natural gas bubbling up. It could even be lit on fire. Finally Hasnat returned and we were able to download all the data since my last visit and upgrade the firmware of the receiver. We finished right at high time and rushed back to the ship to sail to our next stop. Thanks to Hasnat, we were able to accomplish our goals here.
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.
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.
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.
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.
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.
I am once again teaching a Sustainable Development course on hazard in Bangladesh. The highlight of the course is that the 10 students, the teaching assistant and I are all traveling to Bangladesh over Spring Break. However, our plans have been disrupted by the continuing political unrest in Bangladesh. The opposition BNP party is calling for new fair elections by calling for a continuous blockade of travel and periodic hartals – general transportation strikes. They have been trying to enforce it by tossing Molotov cocktails at vehicles that defy it. Over 120 people have been killed so far. The ruling Awami League refuses to give into violence and neither the UN, EU or US
have been able to make a dent in the situation. The two parties and their women leaders hate each other. Neither side will back down on the unrest that started with the Jan 5 anniversary of the election. While more and more people are defying the blockade, after 2 months people have to make a living, the risk is too high to take a bus load of undergraduate students around the country.
Our solution, Plan B, is to stay off the roads and travel the country by boat. Dhaka, the capital is quiet, so we are visiting there at the beginning and end of the trip. The boat we were planning to use to visit the Sundarbans Mangrove Forest came up to Dhaka to meet us after we had a difficult trip. The 14 of us (Chris Small of Lamont and Liz Chamberlain of Tulane University are also joining us) made it to JFK skirting traffic
only to find a 4-hour delay on our flight. The airline nicely rebooted us for the next connection to Dhaka and escorted us through the airport to catch it. However 4 bags missed the connection. By the time we got to our hotel it was midnight and we still hadn’t had dinner. It was two AM by the time we go to bed. My TA, Matt, had to go back to the airport in the morning with Sukhen, but only 3 of the bags arrived. The missing one was Matt’s, but having lived in Dhaka, he had clothes in storage there.
The rest of us went to Dhaka University to meet our Bangladeshi counterparts, 8 students and 2 professors that are traveling with us. After a quick tour of a few spots around Dhaka, we headed to meet the Kokilmoni. I have sailed on her twice before. With Plan B, we will have to skip some areas, like the Brahmaputra River, that we cannot get to by boat in our limited time. However, we will get more time at other spots of interest and see what will be new parts of the country for me from a different vantage point. We started on a the Shitalakhya River east of Dhaka and sailed south in larger rivers finally passing the confluence of the Padma (combined Ganges and Brahmaputra) with the Meghna River before tying up at Chandpur for the night.
A boat is a much more pleasant way to travel than a bus with more places to hang out and rest from jet lag. The food is good and plentiful. The cabins are tiny and hot, while the showers are cold. The main thing the students missed is any opportunity to buy Bangladeshi clothes. Along the way we made two quick stops, one above and one below the confluence, for Liz to take samples for OSL analysis, a dating technique that uses electrons trapping in quartz to determine the last time the sediments were exposed to sunlight. The samples, collected by hammering a tube into the outcrop, must not be exposed to sunlight. Otherwise, these first days are quiet as it will take us until tomorrow afternoon to reach our first extended field stop. Boats are a comfortable, but slow way to travel.
It was time to pack up and leave. Shofiq, who is from Sylhet, was dropped off near his home and the fellowship of the rocks was broken. We settled in for another long drive. We made an impromptu stop at one of the numerous brick factories scattered across Bangladesh. Here, the workers immediately started snapping pictures of us with their phones. We walked past the rows of drying unfired bricks to the massive kiln built from the bricks themselves. We saw them feeding coal into the hot, actively firing part and unloading bricks from the completed quadrant. This would be followed by loading of raw bricks for the 12-hour firing. This factory makes around 9,000,000 bricks in the six-month season. Although it was their lunch break, they demonstrated the mixing of the mud with a little sand and let me carry a half-full wheelbarrow load to where the bricks were
shaped. I spilled a full load when I tried to move it. The experienced brickmakers took about 30-seconds per brick.
We stopped for lunch at the same roadside restaurant, then went to find Wari-Betashwar. Getting to the archeological site was not easy, but a mixture of my hand-held GPS with a Landsat image and a Bangladeshi phone with completely inaccurate Google maps eventually got us there a little after 4 p.m. We toured the site with the chief archeologist, but all the excavations had been filled in to protect them during the off-season. As we walked around the 600m by 600m protective wall, Prof. Rahman explained the history of the site. This urban
center was founded around 500 BC on land slightly uplifted by one of the anticlines. The slight extra elevation protected the land from flooding. The site was by the side of an old path of the Brahmaputra River and was thus a major trading center. Artifacts from as far as Greece and Rome were found here. After a gap in the record, the city flourished again in the 7th century AD, before being abandoned. The rise and fall of the center may be tied to avulsions, or switches in position of the Brahmaputra, making the site an interesting confluence of tectonics, rivers and people.
Continuing on, the students got a taste of Dhaka traffic as we approached our hotel near the airport. Now came the real
splitting up of the group. The foreigners would stay overnight to begin our return home, while the Bangladeshis would fight the traffic to return to Dhaka University and their homes. Many of us spent most of the time until our 2:30 a.m. departure talking. Twenty-three of us and our luggage and equipment managed to squeeze into a 21-seat bus and made it to the airport. Now, once again problems with our tickets arose. While most of us were fine, almost half only got boarding passes as far as Abu Dhabi, or none at all. Eventually they fixed the problem for most of them, and all of us were able to board the delayed aircraft. The delays here and in the flight to New York and Chicago will mean that the vast majority will miss connections. At least my nightmare scenario of missed flights and connections was happening on the way back. Not the smoothest ending, but it has been a great trip and a very successful field school. Several of the students are trying to figure out how to get back to Bangladesh, and a lot of lasting friendships and connections have been made.
The drive from Tangail to Sylhet turned out to be grueling. We took a longer route that skirted Dhaka to avoid the traffic jams that people hit earlier in the week. Unfortunately, with the slower buses that route took 13 hours. We didn’t hit our lunch stop until 4:30 p.m., where Badrul and Ashraf had been waiting to join us for five hours. It was dark by the time we drove past the first anticlines, and we didn’t get to the resort until 11 p.m. We picked our roommates, got our rooms and had a very late dinner. Most field trips have a “death march” hiking a long way through forest, swamps, hills or deserts to get to a remote outcrop. We have a “death bus ride” instead.
The new resort where we were staying was tucked away in a corner of Bangladesh along the Shari River about a kilometer from the Indian border. With a cold pool and only slightly warmer not-hot tub, views of the woods and hills, this is by far the nicest place I’ve stayed in Bangladesh. Given the late arrival, we delayed the start of the classroom day by an hour. The classroom was in a separate building closer to the river The first classroom day covered the stratigraphy and structure of the sediments and rocks we would see the next day. With lots of questions, the day ran late.
We started early and argued over an outcrop on the driveway of the resort. We continued down to the Shari River, where I had previously visited the geology by boat. Numerous
country boats were mining and transporting sand from the river. We worked along the shore, climbing over and visiting outcrops. The beds dipped steeply into the ground, folded by the tectonics, but also provided evidence that a large braided river used to flow here. One possibility is that it was the Brahmaputra from a time before the uplift of the 2 km-high Shillong block pushed it 200 miles to the west. Eventually, we could not go farther along the river. We took an inland path farther north, but when we rejoined the shore, we were blocked again. A short time later, after a conversation with the Bangladeshi border guards stationed here, they flagged us a passing boat. It ferried us across the river, but not before
several on our party practiced their cliff jumping technique.
After spending some time on an outcrop where we were filmed last year, we took an inland path. Along the way we met Johnny the elephant, and a few groups of students got elephant rides. We continued past tea gardens and rice paddies and finally emerged to a large outcrop of shallow marine sediments along the river. At this earlier time, the coastline was north of us, and the delta was prograding to the south as a result of all the sediments eroding from the Himalayas. The younger river sediments we had seen earlier had been deposited after the coast had pushed past here. We stopped for lunch, looking across the river at the India-Bangladesh border and a pile of watermelons waiting for a
boat to take them downstream. Two students swam across and purchased two for dessert. Then Badrul flagged down a large boat to taxi us downstream back to where we started.
After a few geology stops along the way, we reached Jaflong. At this site, there is a mixture of mining of sands and gravels from the river, and tourists looking to view the massive Shillong uplift in India. We stopped at an overlook near our GPS and seismology stations. Then a group of us descended to some outcrops and the chance to join the tourists at the international border. The river had shifted a little since I last was here, and now the best viewing site was officially in India. The Indian and Bangladeshi border guard let us and everyone else cross the
border to the little spit of land for a better view. Many photos later, we walked back to the buses and returned to the resort. Dinner was delayed and about half of us took the opportunity for a dip in the freezing pool to rinse off the sweat and grime.
Our final classroom day conversation included multiple aspects of the interaction of the rivers and the tectonics that our project focuses on. We ended with several students presenting their research from places across the globe. The last item was a group photo close to the Shari River. The last field day took us farther southwest to Sylhet City itself. The Cricket Stadium is surrounded by outcrops that we walked around, passing a pet monkey as well. After lunch at the stadium and a peek inside, we had to make a decision. There was not enough time for
both the outcrops at the airport and shopping in Sylhet. The group split, and each bus went to one of the sites. I chose the outcrop. The river sediments at the airport were clearly different from the stadium and showed that the sediments were deposited while the 80m-high Sylhet anticline was growing. They were muddier where the anticline was tilting the land northwards, and sandier with gravels on the other side of the anticline where the southward tilting had steepened the river. We headed back, stopping to at least buy some tea from the region. However, we got back too late to hold the bus vs. bus cricket match. Just some practice would have to do, until the BBQ that evening.
It has been an incredibly busy week. We have had between 42 and 48 people here for the field school, including 35 students and 12 instructors (seven to 10 at a time). The first day was very light for the jet-lagged students, just a short introduction to the field school and some background, and then introductions all around as we started to get to know each other. The final group of nine students finally arrived around 9 p.m. They were the most worn-out, bedraggled bunch of travelers I have ever seen.
After a good night’s sleep we started on the first classroom day. Our full five days near the Brahmaputra River would focus on the river processes and the stratigraphy they produce. We stopped the lectures at 4 and all piled into the bus
to see the embankment built to protect the city of Sirajganj from the westward migrating river. As is often the case in the dry season, they were repairing the embankments from last summer’s collapses. We rented two country boats and sailed along the embankment and walked back to the buses on the top of it. It is an impressive structure, but in need of continual repair to keep up with the river.
The next two days were spent on the river and its mobile islands, called chars. Setting up the equipment for the river surveying was hampered by a lack of power for drilling holes. A Bangladeshi drill and bow solved the problem, but not before rearranging the schedule. On the first day we all visited the char near the 5 km
Bangabandu Bridge over the river. We spent the day viewing sedimentary structures and seeing the villages on this island that is almost entirely underwater during the monsoon. For the second day, we had to split the group. One contingent joined Jim Best as we surveyed the river with an ADCP, which measures water velocities from the top to the bottom of the river, and a sidescan that provides images of the bottom on either side of the boat using sound. The other, yielding to student requests, went to Tangail, the nearest city, for shopping. When everyone returned, we held a cricket match, with most Americans learning the rules on the fly. We finished the five overs per side as darkness fell.
We went back to the classroom the next day for more lectures on remote sensing of changes on the delta, stratigraphy,
subsidence and arsenic contamination. The hands-on experience was analysis of two sets of well samples that had been drilled the days before. Everyone had a chance to describe the samples, measure magnetic susceptibility and use a portable XRF machine to measure chemistry. We have found that magnetic susceptibility and strontium content are a good way to characterize whether sediments have come from the Brahmaputra River or not.
Finally, our last field day here was doing a resistivity imaging survey over the two bore holes and across the boundary between the Brahmaputra floodplain and the upland strata of the Madhupur tract. Generations have debated whether the transition is a fault contact or not. We would collect some data to try to answer the question. The students also got
to visit another tube well being drilled. Tube wells, drilled primarily for drinking water, is a local drilling method whereby a team of a handful of people can drill a 100m well in a day by hand. After everyone helped set up the 750m long resistivity line, most of the American students went to see the tube well drilling. The Bangladeshis, who have all seen tube well drilling, stayed with me to help run the resistivity line. As it turns out, Liz Chamberlain was pulled into a local villager’s home to have her hands tattooed with henna by a woman and her daughters. She missed the tube well drilling, but gained an exciting personal experience. It was also the first time the students were in a Bangladeshi village. We were the center of attention and many photos were snapped by both sides. We gathered up the resistivity equipment and then had informal student
presentations before the final night barbeque. We had successfully completed the first half of the course, and all the students (and instructors) were bonding.
Feb. 21 is Language Day in Bangladesh. It is a holiday, now adopted by the UN as International Mother Language Day. It commemorates a day in 1952 when a crowd of Bengali students protesting Pakistan’s adoption of “Urdu and only Urdu as the official language of Pakistan” were fired upon by the police. It marks the beginning of the move towards the independence of East Pakistan, the future Bangladesh, from Pakistan. It is a time of plays, book fairs and poetry reading celebrating the Bengali/Bangla language. There are also laying of flower wreaths at the Shahid Minar, the monument where the killings occurred near Dhaka University, and many smaller copies throughout the country.
For us, it was a travel day. A long eight-hour drive from Khulna in SW Bangladesh across the Ganges River and the Jamuna River, as this section of the Brahmaputra is known, to our home for the next week. The eight of us in our
party left the Bawali in two vans, stopped to pickup equipment, and settled in for a long uneventful drive, or as uneventful as driving in Bangladesh can be.
The next day my group went to Mawlana Bhashani Science and Technology University to try to install a new GPS. After various meetings and cups of tea, we explored the rooftops looking for the perfect site for the antenna. Unfortunately, the building we were in was not quite finished. It was a good site, except the columns on the roof were still a mass of rebar and the concrete was yet to be poured. More meetings, coffee, sweet desserts, and we checked out other roofs. Many buildings at the relatively new university are unfinished. The older finished ones are lower and the clear view of the sky we need is blocked by trees. The
first roof was the best choice, but would not be ready for three months. The best we could do was to set up the GPS box and leave all the equipment there. Humayun will come and finish the job in May. Without the installation work, we continued to meet people and have tea, lunch and more tea. We finally left around 4. Time to go back to the Elenga Resort, where we were staying, and prepare for the arrival of students for the Field School.
Our NSF grant from the PIRE (Partnerships for International Research and Education) has a large emphasis on providing American students with international research experience. One of the things we proposed was a two-week Field School in Bangladesh. We have 15 U.S. students, 15
Bangladeshi, a few other invitees (France, Singapore, India) plus the scientists and students from our project and our advisory board. Most were scheduled to arrive on Sunday. During the day, I started receiving messages about delayed and cancelled flights. My nightmare scenario was arrivals scattered over several days with no way to know where or when. Most of the delays were absorbed by the long layovers at JFK and O’Hare, where experienced Bangladesh hands would lead them to the promised Field School. Our travel agent shifted one of the cancellations to another flight.Then I learned that Steve Goodbred, leader of the JFK troop, had his flight cancelled and would fly a day later. Mike Howe, a grad student with one trip to Bangladesh, was in charge. Worse, the flight was delayed and could miss its connection in
Abu Dhabi. One student was MIA. I stayed up late to follow the flight and, yes, it missed the connection. I went to bed thinking that most of the U.S. students would be a day late.
I awoke early to find that they had been rebooked through Delhi and would arrive late afternoon. Better still, I learned that the missing student had been rebooked to the Chicago route. Then Humayun called and asked if I was meeting the on-time group for breakfast. I rushed out and Babu drove Chris and myself to the Parjatan restaurant across from the Martyr’s memorial. We got there just after they did. We had breakfast and then dodged traffic to cross the street to the memorial. While there, the Dhaka University contingent arrived for breakfast and we joined them. The Field School was on. Three-quarters of the people had arrived; most of the rest would be here by dinner. Only Steve and Ryan would be a day late.
When we got cell phone signal back, we found things did not go according to plan. Scott’s flight had a medical emergency that required a stop in London, so he missed his connection. So did the GPS box, so they both arrived the morning of the 18th. He was not in Khulna already working. He wasn’t working on the compaction site. Between the flight delays and the ship delays, we had lost a day.
Since I couldn’t meet Scott, it was best for me to go to Polder 32 to check on the GPS there. However, not knowing the situation, we had sailed up the wrong channel. We wouldn’t get to the Polder 32 site until the afternoon. Polder is a Dutch term for an embankment. They have been built around much of the land in coastal Bangladesh to protect it from flooding from the brackish water and
improve farming. An unexpected side effect is that the protected land inside the polder, with no flooding or sediments, has sunk by over a meter. It is lower than the land outside the wall and lower than high tide. When Cyclone Aila hit the area in 2009, it breached the polder and the island was flooded for almost two years. We are studying both the physical environment and the human impact. My part is measuring the subsidence with GPS. The receiver here has a modem so the data can be collected by phone, but it hasn’t worked since Jan. 1. We went to the school that houses it, and I managed to correct the problem.
Now it was time to join Scott. I left the boat for a bumpy 2.5-hour drive to Khulna and the hotel. We had allotted two days for servicing and installing GPS in Khulna, but we also wanted to visit a 400-year-old temple in the Sundarbans. It is being looked at to measure subsidence since it was built. We could only visit the temple if we could do the GPS work in one day. We started a 7 a.m., picking up Hafizur and heading to his family’s house, where the compaction meter is. We hoped to finish it quickly, but there were problems with the GPS. The solar panel controller was bad and had to be replaced. Then I found the settings of the GPS were bad; I couldn’t communicate with it. After a struggle, I managed. The system went bad last June and had recorded no data since then. Scott collected data from the compaction meter and surveyed the monuments, while
I got the GPS going again. When it was time to leave, we found that the Islamic family had prepared a huge lunch for us, and we had to stay and eat: sweet rice appetizer, two kinds of fish, chicken, vegetable, rice and a rice pastry in palm juice for dessert.
When we left to go to Khulna University (KU), our chance for the temple looked bleak. We met Professor Rakib Uddin, who did not get our sense of urgency. The GPS at KU hadn’t been working for years. Set up in the Urban Planning Department, the 20-year-old receiver needed constant care to keep going. We had installed these obsolete instruments when we first started working in Bangladesh and had almost no funding. We would be reestablishing the site, replacing everything.
Then we would install a new receiver in Rakib’s office in Environmental Sciences. As long as we had some overlap of the two receivers, we could combine the measurements for a longer record. After various formalities, we went to the office. We would need to buy some extra equipment, but the professor had to leave. We called everyone to say we could not do the temple. Then Rakib got the professor to leave the key so we could keep working. It was now a maybe. We arranged for the forest permits not knowing if we could use them. Allan and Towfique went shopping while Scott and I did what we could. By the time they got back and we finished, with multiple time-stealing problems along the way, it was dark. Rakib stayed late and Scott and I rushed to install the new GPS. The new ones are easier to work with, but
everything takes time. By the time we finished it was almost 9 p.m.
We rushed to the hotel and packed overnight bags. Bachchu’s other boat, the Mowali, would take us to the Bawali. We left at 10 p.m. after less than 24 hours in Khulna. It took 4 hours to reach the Bawali west of Polder 32. It was 2 a.m., but we made it. No dinner, but a chance to see the only Hindu Temple in the Sundarban. With two armed guards for tigers and a local guide, we sailed to a small channel south of the temple and took the launch to go into the forest. The channel got smaller, with branches occasionally sweeping across the boat. We got stuck, but the tide was rising. Then we had a long hike through the muddy forest, across a log bridge and more mud.
Finally we got there. After examining the temple, we decided more work was needed before we accepted the low subsidence rate estimated for the site. We also visited the rubble of the home for the local community and their protective wall. They were sent here to protect the region from Arakan and Portuguese pirates. They were the ones who built the Shakher temple. We could head back down the channel and return to Khulna on the Bawali. Despite all the problems, we had accomplished all of our goals for this part of the trip.
In Bangladesh we find that nothing ever goes according to plan, but we have always been able to accomplish our goals. So far on this trip, we have had to adjust from before we even got on the plane. The snowstorm on Feb. 13 cancelled Scott and his student Allan’s flights to New York from Wilmington, N.C. It looked like they would be delayed by a day, but then it worked out for them to drive to South Carolina to catch a flight. I was then able to pick them up on my way to take them to the airport for our flights to Bangladesh. There were seven of us going there together, but only six made it onto the plane. There were problems with his ticket, probably from the attempts to get to New York, and he couldn’t get it fixed in time to make the flight. Allan’s ticket was OK, though.
Not having Scott meant rearranging our plans. Plan B. We switched the order of things. Allan and I would go to Hiron Point in the Sundarbans mangrove forest first, since I could service the GPS there alone, but needed him for most of the other work. The silver lining was one of my equipment boxes didn’t arrive. It would not arrive until the next day when Scott could pick it up. I didn’t have to delay leaving Dhaka. After stopping by Dhaka University, I headed to Khulna to join Chris Small and others on the M/V Bawali. Chris was able to rearrange his work so we could sail to Hiron Point first. We got to the ship around 4 p.m. after a day of driving and a two-hour ferry ride across the Padma River, as the combined Ganges and Brahmaputra Rivers is known. We waited for Kushal and his students from Khulna University to arrive, then started the trip to Hiron Point near the coast.
We made good time and got to Hiron Point in the morning. We installed a GPS at the forest ranger station near a tide gauge. The tide gauge measures the water level relative to land, a mixture of sea level rise and subsiding of the land. Our GPS measures just the subsidence of the land, accurate to 8 mm each day. The combination of rising sea level and sinking land puts Bangladesh at greater risk of inundation. Thus the sediment deposited by the rivers is critical for maintaining the land and the mangrove forest. So far, it looks like sediment is keeping pace in the natural environment, but there are problems where man has made changes. We installed the GPS in October 2012. While we put in communication equipment, the site is so remote that there was no cell phone signal to download the data. Hence, our visit to collect it manually.
Everything looked fine, but when I tried to connect to the GPS, I couldn’t. The set-up for the communication equipment meant the settings were different and locked. After a frustrating hour of attempts, including a hard boot to reset the system, I finally found the right settings to talk to the device. The trip wasn’t in vain. Downloading the data, I found something had gone wrong last July. We had good data until July 19, then one giant file with a date in 2025. I hope that it actually contains good data, but I won’t know until I get back and can get it to someone to look at it. Even better, my hard reboot cleared out the problem, and the GPS started recording data properly again. Even if we have a data gap, we will still be able to see the data trend for the subsidence rate. Taking two days to come down here was worthwhile.
The next problem was that the Bawali couldn’t get out of the small channel by the ranger station until the next high tide. We were stuck for eight hours. We used the time to explore the channels, but we would not be able to get to our next stop on schedule. Time for another change in plans. We are up to Plan C. We decided to go back so I could get off the boat and join Scott, who has hopefully arrived. We will do our on-land work and then rejoin the Bawali in a day and a half, if all goes according to plan. Not a sure bet on this trip.