Quantifying Rocky Headland Water and Sediment Transport with Coastal Management Implications Website
Several research questions will be addressed in the proposed project:
1. What parameters best define headland transport rates, and how do they scale in importance with the size of the feature and sediment grain size?
2. Are there cumulative, compounding, or mitigating effects of many small adjoining features? In the case of a series of smaller headlands, is their effect on transport best described by a shoreline roughness length?
3. Can a predictive model (reduced complexity model) be developed that can be applied effectively to a large number of headlands along the California coast, substituting for costly field or computer model studies?
4. How do local, headland-scale processes relate to regional littoral-cell-scale sediment budgets? Are present definitions of littoral cells consistent with an improved understanding of the role of headlands in longshore sediment transport?
A three-prong approach is proposed: conceptual model development, a field campaign for relevant data collection, and numerical modeling to test parameter importance. For a robust analysis of headland transport, original data must be gathered from the field that quantifies water and sediment movement. The field data can also be useful for understanding larvae transport, contaminant dispersion and recreational hazards. The field campaign is focused on five headlands of various sizes with this proposal concentrating on the southern California targets of Pt. Dume and Palos Verdes. Prior to study of these southern California sites, our methods and insight will be developed at three sites closer to Bodega Marine Laboratory. Field data collection in southern California will be enhanced by the preceding experiences and also by nearby SCCOOS ocean observing nodes, such as the HF-radar surface-current stations that bracket Pt. Dume (Nicholas Canyon and Dan Blocker). A numerical model (DELFT-3D) will be used in collaboration with researchers from the USGS Pacific Coastal and Marine Science Center in Santa Cruz to examine the importance of physical, geological and hydrodynamic variables across a range of idealized headlands. A predictive conceptual model (reduced complexity model) will be based on the findings from the field campaign and numerical modeling. This predictive model will then be used at multiple headlands to examine existing littoral cell boundaries along the California coast something that has not been scrutinized since the 1970s when Habel and Armstrong (1978) first described these boundaries.
The most notable outcome of the project will be the predictive conceptual model to estimate circulation and sediment transport around differently sized headlands on the coast of California. We expect that the predictive model will be used to improve sediment management on beaches and offshore by evaluating the efficacy of beach nourishment near headlands. This will benefit coastal zone managers in California including state and federal agencies (Coastal Commission, USACE), regional bodies (BEACON), and local municipalities, as well as marine ecologists and biologists. As coastal communities prepare climate change adaptation plans that consider beach nourishment, such as AdaptLA, the predictive model can aid in feasibility assessments for such approaches. Finally, a better characterization of the states littoral cells could influence the integration of physical processes into ecosystem protection zones (e.g., MPAs or ASBSs).
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