In an era of sea-level rise such as has persisted on Earth for at least the past 18,000 years, the landward recession of coastal bluffs is an inevitable natural process wherever tectonic or isostatic uplift rates are lower than the rate of sea-level rise. Responsible development, and California law, requires that new structures be sited a sufficient distance landward of a coastal bluff that their stability shall be assured over their expected economic life, and that they will not require the construction of coastal armoring over that same time interval. Because coastal bluffs are dynamic, evolving landforms, establishing structural setbacks for coastal bluffs is a far more complex process than for manufactured or natural slopes not subject to erosion at the base of slope. This talk will present some of the considerations for development and redevelopment in this challenging environment

Mark Johnsson is an Earth system scientist trained as a clastic sedimentary geologist. His principal professional interests are in the broad field of erosion and weathering. He is interested in geotechnical issues related to development in coastal regions, and in controls on chemical weathering and erosion in general. Johnsson has served as staff geologist for the California Coastal Commission since 2000, and in that capacity serves as a technical advisor to the Commission and its staff on geologic and geotechnical issues related to development in the coastal zone. Prior to joining the Coastal Commission, Johnsson worked as a research geologist for the U.S. Geological Survey and taught in the Earth Systems Program at Stanford and the Geology Department at Bryn Mawr College. Johnsson received his PhD from Princeton University in 1989, and continues to do research into the system controlling the composition of clastic sediments and its relationship to global geochemical cycling and landscape evolution. A California-licensed engineering geologist and hydrogeologist, Johnsson is the author of some 40 papers and books, and has advised some 15 theses and student research projects.