Coastal Protection Under a Changing Climate

Due to seismic deflection and subsidence parts of California’s north coast are both increasingly desirable to develop and increasingly vulnerable to changes in storm patterns, sea level rise, and natural disasters such as tsunamis. Coastal communities are on the frontline of global climatic changes and are under increasing pressure to assess their vulnerability and develop adaptive strategies to current and anticipated changes. This session provides an overview of how communities around Humboldt Bay in Northern California are evaluating their future and prioritizing a combination of adaption strategies ranging from fortification to retreat and including measures inclusive of building or improving upon hard-engineered structures, developing living shorelines, and enhancing natural buffers, to name a few.

More specifically, this course will provide a methodology for assessing local sea level rise from a combination of eustatic sea level rise (SLR), tide gages, land leveling, and analysis of geologic uplift and subsidence. Once local SLR trajectories are determined relative to land level, an assessment of community vulnerabilities is conducted. Adaptions are then developed to mitigate vulnerabilities.

While dikes, sea walls and other traditional infrastructural elements are considered, they are not in themselves a sufficient solution. Even with fortification, higher tides can inhibit upland stormwater drainage without a network of pump stations. Higher sea levels can also cause groundwater to rise on the inboard side of fortifications reducing permeability converting near shore grasslands to wetlands. Moreover, higher tides can hasten saltwater intrusion. Conversion of landuse designations and phased partial retreat must be considered in some cases. Enhancement of natural dunes, salt marshes, estuaries, living shorelines, as well as conservation lands, agricultural fields, and other areas in which volumetric capacity of water bodies can be increased to attenuate higher tides may also be considered.