Seacliffs comprise the majority of the world’s coasts, where almost one quarter of the global population reside. Seacliff erosion threatens coastal structures, public property, recreational resources, public safety, and major transportation corridors along the California coast . To combat these problems, seawalls are increasingly used to prevent erosion. However, coarse grained seacliffs contribute sediment to beaches, and preventing seacliff erosion through armoring reduces the beach sediment input. Effectively managing coastal areas will become increasingly challenging as coastal populations and sea levels continue to rise.
LiDAR has rapidly emerged as the modern standard for mapping large-scale coastal erosion.
LiDAR detected negative (reds) and positive (blues) vertical elevation change at San Onofre State Beach, CA between 1998 and 2010
Cliff collapse in Del Mar, CA, 31 October 2018
Erosion of a 2.5 km-long cliff in De Mar was observed weekly for 3 years with a truck-mounted LiDAR. Waves at the cliff base were measured with buried pressure sensors. Cliff erosion rates, incident wave heights, wave-cliff impact, and rainfall were all elevated during winter. The high temporal resolution over multiple years allows separation of erosion from wave and rainfall by, for example, isolating time periods with no rainfall and high wave runup. Upper cliff erosion was most correlated with rainfall, and lower cliff erosion with wave impacts. The cliff is attacked from above by rain and below by waves.
Young, A.P., H., Guza, R. T., Matsumoto, H., Merrifield, M., O'Reilly, W. C., & Swirad, Z. (2020), Three years of weekly observations of coastal cliff erosion by waves and rainfall, Geomorphology, in press.
Thompson, C. F., Young, A. P., & Dickson, M. E. (2019). Wave impacts on coastal cliffs: Do bigger waves drive greater ground motion?. Earth Surface Processes and Landforms. doi: 10.1002/esp.4712
Young, A. P., Flick, R. E., Gallien, T. W., Giddings, S. N., Guza, R. T., Harvey, M., & O'Reilly, W. C. (2018). Southern California coastal response to the 2015–2016 El Niño. Journal of Geophysical Research: Earth Surface, 123(11), 3069-3083. doi: 10.1029/2018JF004771
Young, A. P. (2018). Decadal-scale coastal cliff retreat in southern and central California. Geomorphology, 300, 164-175. doi: 10.1016/j.geomorph.2017.10.010
Palaseanu-Lovejoy, M., Danielson, J., Thatcher, C., Foxgrover, A., Barnard, P., Brock, J., & Young, A. (2016). Automatic delineation of seacliff limits using lidar-derived high-resolution DEMs in Southern California. Journal of Coastal Research, 162-173. doi: 10.2112/si76-014
Young, A. P., Geomorphology, Burvingt, O., & Flick, R. E. (2016). Observations of coastal cliff base waves, sand levels, and cliff top shaking. Earth Surface Processes and Landforms, 41(11), 1564-1573. doi: 10.1002/esp.3928
Earlie, C. S., Young, A. P., Masselink, G., & Russell, P. E. (2015). Coastal cliff ground motions and response to extreme storm waves. Geophysical Research Letters, 2014GL062534. doi: 10.1002/2014GL062534
Young, A. P. (2015). Recent deep-seated coastal landsliding at San Onofre State Beach, California. Geomorphology, 228, 200-212. doi: 10.1016/j.geomorph.2014.08.005
Young, A. P., Flick, R. E., O'Reilly, W. C., Chadwick, D. B., Crampton, W. C., & Helly, J. J. (2014). Estimating cliff retreat in southern California considering sea level rise using a sand balance approach. Marine Geology, 348, 15-26. doi: 10.1016/j.margeo.2013.11.007
Young, A. P., Guza, R. T., Dickson, M. E., O'Reilly, W. C., & Flick, R. E. (2013). Ground motions on rocky, cliffed, and sandy shorelines generated by ocean waves. Journal of Geophysical Research-Oceans, 118(12), 6590-6602. doi: 10.1002/2013jc008883
Olsen, M. J., Young, A. P., & Ashford, S. A. (2012). TopCAT-Topographical Compartment Analysis Tool to analyze seacliff and beach change in GIS. Computers & Geosciences, 45, 284-292. doi: 10.1016/j.cageo.2011.11.007
Young, A. P., Guza, R. T., Adams, P. N., O'Reilly, W. C., & Flick, R. E. (2012). Cross-shore decay of cliff top ground motions driven by local ocean swell and infragravity waves. Journal of Geophysical Research-Oceans, 117(C06029). doi: 10.1029/2012jc007908