Life on a tectonically active delta; Convergence of Earth Science and Geohazard Research

This PIRE project brings together an international team of U.S., Bangladeshi, Indian, German, and Italian scientists to further our understanding of the dynamics of the world's largest delta, the Ganges-Brahmaputra-Meghna Delta (GBMD). This delta, named for the three large rivers that flow into it from the Himalayan and Burmese Ranges, encompasses most of Bangladesh. In addition to its size, this delta is notable because it is at the active juncture of three tectonic plates, and receives over one gigaton of sediment annually from the three large rivers. About 1/3 of this sediment remains in the delta because it is rapidly sinking. This combination preserves a tremendous stratigraphic archive of erosional processes in the Himalaya, the river-based processes that are building the GBMD, the tectonics of the active plate boundaries it overlies, and the interactions among these processes. This record is largely unexplored and little is known about the fundamental interactions between sedimentation and tectonics at this scale. This PIRE team will use a broad suite of disciplines and techniques to collectively study the sedimentary and hydrological processes, tectonics, structural geology, and seismology essential to unravelling GBMD dynamics.

The PIRE team will first create a record of the stratigraphic architecture of the delta using a mixture of advanced technical and local manual methods. Core areas of the project include: 1) defining the tectonic plate boundaries that are buried by sedimentation; 2) identifying potential sources of future earthquakes; 3) investigating the causes of the subsidence rates due to longer term effects (e.g., sediment loading, tectonics, and compaction) vs. shorter term effects (e.g., earthquakes and human interventions); 4) investigating rapid channel switches of the Ganges and Brahmaputra rivers; and 5) assembling a comprehensive, integrated record of delta dynamics by coupling tectonics and hydrological processes, and by linking long-term steady processes with abrupt, short-term events.

Bangladesh is a developing country that is the size of Iowa, but with a 50-fold greater population of almost 160 million people. This impoverished nation is extremely vulnerable to natural hazards related to the dynamism of the delta system. Such hazards include widespread seasonal flooding, river erosion and channel redirections, permanent land loss from sea level rise, naturally-occurring arsenic in groundwater, recurrent cyclones and monsoons, landslides, and huge earthquakes. Because the infrequent geologic events are poorly understood, there is little long-term planning to address the timescales at which the dynamic GBMD landscape is changing, leaving a growing population at risk. Reliable knowledge of geologic processes is therefore a prerequisite for effective infrastructure design, risk-reduction and resource optimization in Bangladesh.

The PIRE project provides a compelling international education opportunity for all participants by collaboratively engaging them in research on an important fundamental problem, the results of which could reduce the impact of future delta-related hazards. It will train the next generation of U.S. earth and environmental scientists to work globally via international fieldwork, laboratory experiments and analysis, and modelling. Graduate students and undergraduates from PIRE institutions will be able to enrol in interdisciplinary field courses and schools in Bangladesh; additional research trips and field schools will also be open to students from institutions not directly involved in the PIRE research efforts. The project will also broaden participation across PIRE institutions and strengthen the geosciences dimensions of an interdisciplinary course on water issues in Bangladesh taught at the University of Minnesota.

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