HR: 16:00h
AN: H34B-01 INVITED    [Abstracts]
TI: Initial Modeling of the Large-Scale Interactions Between Lithology and Coastal Processes on Rocky Coastlines
AU: * Murray, A
EM: abmurray@duke.edu
AF: Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Box 90230, Durham, NC 27708-0230, United States
AU: Littlewood, R
EM: ryan.littlewood@duke.edu
AF: Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Box 90230, Durham, NC 27708-0230, United States
AU: Limber, P
EM: patrick.limber@duke.edu
AF: Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Box 90230, Durham, NC 27708-0230, United States
AU: Slott, J
EM: jordan.slott@duke.edu
AF: Nicholas School of the Environment and Earth Sciences; Center for Nonlinear and Complex Systems, Duke University, Box 90230, Durham, NC 27708-0230, United States
AB: The large-scale evolution of rocky coastlines involves the interactions between: 1) coastal erosion and sediment- transport processes; 2) coastline shape and topography; 3) variations in rock strength and composition; and 4) tectonics. We will present an initial model exploration of some of the interactions among the first three influences, and how those interactions shape the plan-view coastline over time. In the simplest case, with spatially uniform lithology, after a rapid sea-level rise, wave-driven coastal processes modify an initially fractal coastline. (The fractal nature results from the intersection of sea-level with a fluvially or glacially sculpted landscape.) Sediment production and alongshore transport creates pocket beaches. As sediment accumulates and headlands retreat, these pocket beaches expand and coalesce, ultimately producing long, straight sections of beach backed by cliffs where the most recent headlands existed. Southernmost California (Orange and San Diego Counties), USA, seems to exemplify an approach to this state. As sediment- transport pathways lengthen, nearshore canyons, which act as sediment sinks, strongly influence coastline evolution. Understanding how and where nearshore canyons appear and evolve over long timescales may be one of the greatest needs for exploring this style of rocky coastline evolution. Numerical modeling also suggests that alongshore heterogeneities in rock strength (maximum weathering rates) can produce a headland/pocket beach morphology, and that the cross-shore amplitude of the headlands can grow over time. However, these results are only relevant in an environment where sediment is lost to deep water at a relatively high rate—as may be expected, for example, during rapid sea-level rise on a steep coastline. Many processes not addressed in these modeling endeavors also affect rocky-coastline shape, especially on spatial scales less than kilometers; this initial exploration is only intended to illuminate some of the possible key interactions affecting the large scale evolution of rocky coastlines.
DE: 1815 Erosion
DE: 3020 Littoral processes
DE: 3022 Marine sediments: processes and transport
DE: 4558 Sediment transport (1862)
SC: Hydrology [H]
MN: 2007 Fall Meeting