Title

Understanding the behaviors of fluvially dominated deltas using a forward numerical model

Presentation Type

Event

Start Date

27-4-2019 10:50 AM

End Date

27-4-2019 11:29 AM

Abstract

Fluvially dominated river deltas are depositional landforms that produce a sediment prism at the intersection of the two waterfronts.This setting provides regional data of past paralic dynamics and the interplay of organic sediment accumulation and delta formation. The aim of this project is to understand the behaviors of fluvially dominated deltas under allogenic and autogenic forcing using a forward numerical model; Autogenic and allogenic forces are characterized as internal and external dynamics. This model contains a linearly geometric delta shape that assumes sediment mass balance, and tracks the trajectories of two moving boundaries: the shoreline and the alluvial bedrock transition. The shoreline is defined as the boundary where the delta meets the water basin, and the alluvial basement transition is where the sediment prism meets the non-erodible basement rock. Model results demonstrate how the boundaries move due to changes in slope and sea level variations. This forward model also accounts for autobreak. Autobreak is determined when the shoreline separates from its subaqueous component under changes in migration direction. The two directions the model plots are coastal onlap and offlap; during coastal onlap the shoreline of the sediment prism extends towards the saline water basin and during coastal offlap, the shoreline shifts towards the fresh water.Sediment left behind when the shoreline moves further inland is accounted for in the model. Further extension will contain sea level cycles, and the inclusion of the fresh to salt water boundary. These additions will explore how both outside forcing and internal dynamics plays a role in organic sediment accumulation within deltaic formation.

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Apr 27th, 10:50 AM Apr 27th, 11:29 AM

Understanding the behaviors of fluvially dominated deltas using a forward numerical model

Fluvially dominated river deltas are depositional landforms that produce a sediment prism at the intersection of the two waterfronts.This setting provides regional data of past paralic dynamics and the interplay of organic sediment accumulation and delta formation. The aim of this project is to understand the behaviors of fluvially dominated deltas under allogenic and autogenic forcing using a forward numerical model; Autogenic and allogenic forces are characterized as internal and external dynamics. This model contains a linearly geometric delta shape that assumes sediment mass balance, and tracks the trajectories of two moving boundaries: the shoreline and the alluvial bedrock transition. The shoreline is defined as the boundary where the delta meets the water basin, and the alluvial basement transition is where the sediment prism meets the non-erodible basement rock. Model results demonstrate how the boundaries move due to changes in slope and sea level variations. This forward model also accounts for autobreak. Autobreak is determined when the shoreline separates from its subaqueous component under changes in migration direction. The two directions the model plots are coastal onlap and offlap; during coastal onlap the shoreline of the sediment prism extends towards the saline water basin and during coastal offlap, the shoreline shifts towards the fresh water.Sediment left behind when the shoreline moves further inland is accounted for in the model. Further extension will contain sea level cycles, and the inclusion of the fresh to salt water boundary. These additions will explore how both outside forcing and internal dynamics plays a role in organic sediment accumulation within deltaic formation.