22. Ultra High-Resolution and High Frequency Change-Detection of Beach Face and Coastal Sea-Cliffs

Shoreline erosion of beach sand exposes weak coastal cliffs to potential wave attack and mass wasting, a chronic land-loss hazard along much of the shoreline of the western United States. Many coastal cliffs are also susceptible to dramatic strength loss and failure when saturated, due to low cohesive strength and tensile stresses near the cliff face. Both of these hazards, wave attack and elevated ground water level, are seasonal processes that when extreme, can move a coastal cliff out of stable equilibrium and cause rapid, punctuated retreat of the coastline. The two failure modes, wave attack and tensile failure of the bluff, affect different portions of the cliff face. The relative importance of these two modes is poorly understood, owing in part to the difficulty in detecting subtle changes in beach faces and coastal cliffs given their highly complex and hard to measure topography.

The primary focus of this postdoctoral position is to develop and model new datasets of beach and coastal bluff change at high frequency temporal scales so that a full understanding of the intricate processes affecting beach and cliff erosion can be achieved. In this regard, the postdoctoral fellow is expected to develop and build upon existing techniques to collect and process high accuracy data sets of coastal bluff and beach face changes in response to annual storm cycles along critical high loss sections of the California, Oregon and Washington Coastlines. Further, the postdoctoral fellow will be expected to develop new methodologies for performing routine multi-kilometer high-accuracy surveys with appropriate geo-referencing (DGPS and ground control) along actively eroding coastlines. Monitoring will involve ultra-high resolution base-line surveys prior to the storm season, followed by a disciplined program of event-based mapping in response to wave-climate indicators that are recorded and transferred real-time by physical oceanographic buoys, and winter storm events. During extreme weather conditions, monitoring will be performed every day or tidal cycle. The fellow will then develop spatial and parametric models for prediction of the locations and conditions that lead to erosion of the beach face and subsequent coastal cliff loss. The goal of this study will be to provide land planners, government officials, and coastal researches a series of datasets that provide clear evidence of the processes affecting distinct sections of coastline and to develop analytical and empirical models that utilize the data to make predictions about future beach and coastal bluff behavior.

The Geo-Engineering Laboratory of the USGS has a number of geophysical and geotechnical project tools available that allow for the creation of high resolution three-dimensional digital terrain models (DTM) and subsurface geophysical and physical property block models of the near surface, including a scanning-laser 3D ground LIDAR (LIght Detection And Ranging) for acquiring DTM data of any natural topographic surface; ground penetrating radar (GPR) apparatus for imaging the subsurface; spectral analysis of surface waves (SASW) systems; and geotechnical sampling and testing apparatus to characterize the strength and erodeability of soil. The fellow is expected to use available tools and introduce new methods to detect and model ultra-high resolution changes in topography at ultra-high frequencies (baseline, weekly, daily, and diurnally as needed during storm events.). The relation between wave activity, beach face morphology and coastal cliff losses will be used to develop predictive tools for coastal slope instability and toe-erosion by storm waves.

The postdoctoral researcher will work with USGS and other researchers on ongoing coastal studies assessing the relationship of near-shore bathymetry and wave climate to beach accretion and erosion processes, and link these processes with coastal cliff land loss. Where engineered armoring is used to protect coastal cliffs, the postdoctoral fellow will monitor the effectiveness of the armoring systems and their influence on land loss of adjacent slopes.

The postdoctoral fellow will have ample opportunities for interdisciplinary collaborations in engineering, geology, oceanography, physics, statistics, spatial data analyses, numerical modeling, and remote sensing. She/he will be a member of a team that includes researchers from the USGS, academia (University of California (UC), Berkeley and UC San Diego) and other federal agencies (NASA and NOAA). The postdoctoral researcher will be at the forefront of coastal hazards research in the United States and will participate in significantly improving our understanding of some of the most important and societally relevant issues faced by the USGS.

Proposed Duty Station: Santa Cruz, CA and Menlo Park, CA

Areas of Ph.D.: Engineering, geology, geophysics

Qualifications: Applicants must meet one of the following qualifications: Research Civil Engineer, Research Geologist, Research Geophysicist, Research Physical Scientist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Personnel specialist.)

Research Advisor: Robert Kayen, (650) 329-4195, rkayen@usgs.gov

Personnel Office contact: Marie Guillory, (650) 329-4112, guillory@usgs.gov

Summary of Opportunities