Meeting:Abstract 2013 CSDMS meeting-022

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CSDMS all hands meeting 2013

Modeling floodplain dynamics: Can the Ganges-Brahmaputra Delta keep pace with 21st century sea level rise?

Kimberly Rogers, CSDMS/INSTAAR, University of Colorado Boulder Colorado, United States. kgrogers@colorado.edu
Irina Overeem, CSDMS/INSTAAR, University of Colorado Boulder Colorado, United States. irina.overeem@colorado.edu


[[Image:|300px|right|link=File:]]Sediment delivery to low-lying coastal zones must keep pace with, if not exceed, the rate of sea level rise in order to maintain a positive surface elevation. Deltaic lowlands are vulnerable to both sea-level rise and changes in river discharge, but whether the floodplains and coastal areas will ultimately drown depends on a balance of aggradation, eustatic sea level rise and subsidence. The Ganges-Brahmaputra (G-B) Delta is an example of a densely populated coastal system that could be flooded by rapid sea level rise within the next century. Annual monsoonal river flooding and cyclonic storm surges are the principal mechanisms by which sediment is distributed across the G-B floodplain and coastal plain. Stratigraphic reconstructions show that sedimentation in the upper floodplain was more than doubled under the Early Holocene enhanced monsoonal regime, suggesting that the delta may withstand an increase in monsoonal intensity, flooding, and tropical cyclones that are currently predicted in ensemble Community Climate System Model scenarios.

In an effort to improve predictions of climatic forcing on aggradation rates in the G-B floodplain and lower delta, direct sedimentation measurements are paired with a series of model components coupled within the CSDMS Modeling Tool (CMT). A sediment flux model, a floodplain sedimentation model and a tidal-plain sedimentation model will be linked to explore the response of the G-B river system to a future sea-level rise and changes in river discharge. Model algorithms will be validated by sedimentation data collected in 2008 and 2012 from the tidal delta (The Sundarbans National Reserve mangrove forest) and the highly cultivated fluvial-dominated delta plain. Field data will also be compared to model outputs by constraining the spatial patterns of sedimentation across the delta front. In this talk, we present initial sedimentation results and discuss controls on heterogeneous patterns of deposition in the tidal versus fluvial dominated parts of the delta. Early results from individual model components will also be discussed in an attempt to integrate current understanding of the G-B System into a numerical modeling framework.