Search

Stephenson, W.J. and Abazović, A. 2016. Measuring Coastal Boulder Movement Under Waves Using Tri-Axial Accelerometers. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 607-611. Coconut Creek (Florida), ISSN 0749-0208. Boulder entrainment under tsunami or storm wave conditions has been a topic of interest among coastal geomorphologists for the last 25 years. Efforts have been directed to understanding the dynamic conditions under which boulder entrainment occurs and in particular the energy levels required to move boulders of specific sizes. Recent focus on storm waves has highlighted the complexity of the process and that more energetic tsunami waves are not always needed to move larger boulders. Consequently attempts have been made to develop better empirical equations to predict wave height or flow velocity and differentiate between storm waves and tsunami. However, data collection methods are restricted to hindcasting flow conditions based on boulder size, the chosen empirical equations and assumptions regarding historical storm or tsunami events. Significant advances could be made using real time entrainment data of boulder movement alongside flow conditions. This is particularly true if movement type, e.g. suspension, rolling or sliding can be distinguished. This paper demonstrates the use of small and inexpensive tri-axial accelerometers manufactured by Gulf Coast Data Concepts. The accelerometers were placed in PVC water tight housing then located in holes cored into boulders and deployed in conjunction with wave pressure transducers on the shore platform. Movement of 4 boulders were observed by logging real-time accelerations during a 5 day deployment. Preliminary data demonstrated that boulders rolled and moved up to 3 m in a westerly direction, while wave heights were less than 0.7 m, demonstrating of the viability of this technique. [ABSTRACT FROM AUTHOR]

Poate, T.G.; Masselink, G; Austin, M.; Dickson, M.E., and Kench, P., 2016. Observations of Wave Transformation on Macro-Tidal Rocky Platforms. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 602-606. Coconut Creek (Florida), ISSN 0749-0208. Correctly predicting the transformation of ocean waves across rocky platforms has direct implications for cliff stability modelling, coastal defences and long-term coastal evolution. Wave transformation across rocky intertidal platforms is dependent on the morphological characteristics of the platform, including platform width, slope and roughness, and forcing characteristics, including wave and tide conditions. In this paper we present early observations from four field studies providing detailed measurements of wave processes across contrasting rocky platform sites with wave conditions between Hs = 0.5 m and Hs = 1.9 m, water depths between h = 0.5 m and h = 6.8 m and variable platform morphology. Results show that the relative wave height in the surf zone H/ h is generally larger than in previous studies ( H/ h is c. 0.6, instead of 0.3-0.5) and wave dissipation greater for sites with considerable roughness. [ABSTRACT FROM AUTHOR]

Swirad Z.M.; Rosser, N.J.; Brain, M.J., and Vann Jones, E.C., 2016. What controls the geometry of rocky coasts at the local scale? In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 612-616. Coconut Creek (Florida), ISSN 0749-0208. There is a need to understand the controls on rocky coastal form in order to predict the likely response to climate changes and sea-level rise. Spatial variations in coastal geometry result from inheritance and contemporary processes, notably erosive wave intensity and rock resistance. We studied a 4.2 km long section of coastline (Staithes, North Yorkshire, UK) using LiDAR point cloud data and ortho-photographs. We represented the coast as a series of densely-spaced (25 m) and resampled (0.2 m) 2D cross-sections. GIS-based statistical analysis allowed us to identify relationships between coastal morphology, geology (lithology and rock structure) and wave intensity. We found the following statistically-significant relationships: 1) more intensive waves and weaker rocks are associated with steeper shore platforms, 2) higher platforms and cliff toes are associated with weaker and more variable rocks, and 3) surface roughness increases with greater wave intensity, decreased density of discontinuities and decreased variability of intact rock hardness. However, these relationships are weak, which suggests the potential role of coastal inheritance and/or the need to better represent rock resistance in coastal models. [ABSTRACT FROM AUTHOR]

Silva, R.; Martínez, M.L.; Hesp, P.; Catalan, P.; Osorio, A. F.; Martell, R.; Fossati, M.; Miot da Silva, G.; Mariño-Tapia, I.; Pereira, P.; Cienfuegos, R.; Klein, A., and Govaere, G., 2014. Present and future challenges of coastal erosion in Latin America. The coastal zones of Latin America have many landforms and environments, including sedimentary cliffs, deeply incised estuaries, headlands, barrier coasts and low lying, muddy coastal plains. These forms will respond differently to the expected changes in climate and associated sea level rise, which may produce coastal erosion in the future. Considering the coasts of Latin America overall, erosion is not yet a serious threat, although it is widespread and it is severe in some parts. Major erosion problems are frequently associated with human intervention in sediment supply, with poor planning or with the morphodynamic nature of the coast. Permanent erosional processes, locally or regionally, are caused by tectonic subsidence, deforestation and the fragmentation of coastal ecosystems, land use changes and sediment deficits because of infrastructure built along the coast. In this article we analyse coastal erosion in Latin America and the challenges it presents to the region. We first highlight the relevance of Latin America in terms of its biodiversity; then we describe the population at risk, demographic trends and economic growth throughout the low lying coastal zones. We also examine the vulnerability of the region by analyzing the resilience of key coastal ecosystems after exposure to the most frequent hazards that affect coastal zones in Latin America, namely tropical cyclones, sea level rise, ocean acidification, earthquakes and tsunamis. Finally, we discuss seven case studies of coastal erosion across Latin America. We close the study by pinpointing the main areas of concern in Latin America and explore possible strategies to overcome erosion and thus sustain economic growth, minimize population risk and maintain biodiversity. [ABSTRACT FROM AUTHOR]