Collaborative Research: Disentangling Subsidence - Integrated observations and modeling of vertical land-surface dynamics in the Ganges-Brahmaputra Delta

About This Grant

Coastal regions are vulnerable to flooding from rivers and rising seas, increasing storm strength, and destruction of ecologically-fragile areas. River deltas are especially impacted by the balance between increasing water levels from sea-level rise and tides, and land surface elevation changes. Bangladesh’s Ganges-Brahmaputra Delta (GBD), the world’s largest delta, is a particularly excellent place to investigate this problem. The land is sinking (subsiding), worsening the impact of sea-level rise, but the rivers supply ample sediment to elevate the land. However, there is a mismatch in the distribution of sediment and land subsidence; some areas are maintained by sediments, while others are at serious risk of land loss. This project will combine local, on-the-ground measurements of elevation change with broad satellite observations, and develop a comprehensive numerical model of elevation change. The numerical model will enable synthesis of all measurements and incorporate shallow processes that are missing from most models. Results will contribute to Bangladesh’s coastal planning through established collaboration with government agencies, academic institutions, and non-governmental organizations. This project will support 2 postdocs and 3 graduate students in the U.S. as well as build capacity for students and faculty in Bangladesh. U.S. undergraduate students will participate in the proposed research through internship programs and a capstone course that includes a Spring Break field trip to Bangladesh. The model will have great applicability for use in coastal areas prone to flood risk, especially lowland deltas worldwide including the Mississippi Delta. Unraveling the intersecting processes that contribute to vertical land-surface dynamics is critical for forecasting sustainability of lowland deltas into the future. This project will employ multidisciplinary research that integrates an existing delta-wide network of sediment cores and geospatial instruments with broad-scale, multi-sensor satellite remote-sensing analyses, producing novel high-resolution maps of decadal surface-elevation change, topography, and land-use across the coastal zone. A state-of-the-art poroelastic model will be developed, validated, and applied to coastal Bangladesh. The team hypothesizes that at any given site on the delta, surface-elevation change reflects the vertical integration of sedimentation, near-surface soil consolidation, subsurface compaction of Holocene sediment, and deep tectonic/isostatic response of the lithosphere. Across the delta, surface-elevation change reflects how modern land use restricts surface sedimentation and accelerates consolidation, and how ancient river dynamics constructed the alluvial architecture of compacting Holocene sediments. These hypotheses will be tested with a process-based, holistic understanding of vertical land-surface dynamics, and will guide coastal hazard mitigation and sustainability efforts on the GBD and other deltas that face similar environmental and anthropogenic stressors (e.g., Mississippi and Sacramento-San Joaquin river deltas). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.