Recent sio_cmg items

Facing the Coastal Challenge: Modeling Coastal Erosion in Southern California

Thu, 28 Aug 2003 00:00:00 +0000

Erosion due to natural and human activities poses a challenge to the future of California’s coast. A process-based coastal evolution model is being developed to evaluate the past, present, and future rates of erosion of the southern California coast and present this dynamic environment in a visual format. The model consists of a mobile sediment transport component and a bedrock cutting component, both coupled and operating in varying time and space domains determined by sea level and boundaries of the littoral cell. We will utilize retrospective data from geomorphology, tectonics, sea level, climate, and paleoecology to investigate erosional and depositional processes and rates of change. Correlating the earlier shorelines with past climate conditions and time-stepping the ancient coastlines forward to the modern coastline will serve to validate the model. The model then will project the future evolution of the coastline using three scenarios: a most likely change, a minimum...

Shorerise and Bar-Berm Profiles on Ocean Beaches

Thu, 28 Aug 2003 00:00:00 +0000

A beach equilibrium model is developed that treats the outer (shorerise) portion of the profile independently from that of the inner (bar-berm) portion. The two portions are matched at the breakpoint-bar. The partitioning of the profile in this way is consistent with the different forcing modes on either side of the breakpoint. This formulation utilizes beach profile data not previously available. It is shown that both portions of the profile are well fitted by curves of the form h=Ax/sup m/, where h is positive downward and x is the positive offshore coordinate. Surprisingly, the value of m approximately=0.4 is nearly the same for shorerise and bar-berm and does not change significantly with seasonal beach changes (summer/winter). The principal difference between seasonal profiles is that in winter (higher waves) the breakpoint-bar is deeper and farther offshore while the berm crest is displaced landward. Thus the changes in seasonal equilibria are manifested by simple, self-similar...

Coastal Sediment Transport Concepts and Mechanisms

Mon, 25 Aug 2003 00:00:00 +0000

This chapter identifies and develops the transport processes pertinent to the budget of sediment for a littoral cell. It is intended to provide a conceptual basis for the discussions which follow in Chapters 6 (Sources, Transport Modes, and Sinks of Sediment), 7 (Application of Shoreline Change Models) and 9 (Budget of Sediment and the Prediction of the Future State of the Coast). The processes of primary interest here are the action of waves and coastal currents in eroding and terracing the land and in transporting sediment along the coast; the tractive forces of streams in eroding, transporting and depositing sediments; the effect of changing sealevel on beach erosion; and finally the influence of tides and streams in the maintenance and filling of coastal lagoons. For a more detailed discussion of these processes and their cumulative effects and interaction within the littoral cells of the San Diego Region, refer to CCSTWS 86-1 (Inman, et al., 1986).

Budget of Sediment and Prediction of the Future State of the Coast

Mon, 25 Aug 2003 00:00:00 +0000

Budget of Sediment and Prediction of the Future State of the Coast

Nearshore Processes

Fri, 25 Jul 2003 00:00:00 +0000

Nearshore Processes

Database for Streamflow and Sediment Flux of California Rivers. SIO Reference 98-9