HR: 1330h
AN: OS52A-0892    [PDF]
TI: Morphodynamic Modeling of Response of River Deltas to Sea Level Rise
AU: * Akamatsu, Y
EM: akama001@umn.edu
AF: St. Anthony Falls Laboratory, Mississippi River at 3rd Ave Se, Minneapolis, MN 55112 United States
AU: Parker, G
EM: parke002@umn.edu
AF: St. Anthony Falls Laboratory, Mississippi River at 3rd Ave Se, Minneapolis, MN 55112 United States
AU: Muto, T
EM: tmuto@net.nagasaki-u.ac.jp
AF: Faculty of Environmental Studies, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852 Japan
AB: River deltas have shown a variety of responses to Holocene sea level rise. The mouths of the Thames, Humber and Severn Rivers display deep embayments similar to those of Delaware River and Chesapeake Bay. The mouths of the Maas/Schelde River System show an intermediate degree of embayment, whereas the mouths of the Po and Ebro Rivers show actively prograding deltas similar to that of the Mississippi River. To date most attempts at morphodynamic modeling of the response of a river mouth to sea level rise have relied on the normal flow assumption; that is, the effect of backwater has not been considered in treating river flow. When the rate of sea level rise is sufficiently large compared to sediment supply to the delta, such models predict the autoretreat of a sediment-starved delta. It is suggested here that such an analysis is strictly valid only for rivers with relatively large Froude numbers ($>$ 0.5) in their deltaic zones. Most large rivers have much lower Froude numbers near their mouths, implying that backwater effects cannot in general be neglected. Here a 1D morphodynamic model of delta response including backwater effects is compared with one that does not include them. The former model predicts that when the rate of sea level rise is sufficiently high and the sediment supply sufficiently low, the response is a modified form of autoretreat characterized by the formation of a deep embayment. This feature cannot be predicted with the latter type of model.
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1869 Stochastic processes
DE: 1886 Weathering (1625)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting