Michiel van der Meulen - TNO
Monday 17 April 2023, 09:15-10:00
 

Michiel van der Meulen studied geology at Utrecht University. After obtaining his PhD in 1999, he started working on mineral resources and supplies at Rijkswaterstaat (directorate-general of Public Works and Water Management). In 2003, Michiel joined the Geological Survey of the Netherlands, part of TNO, where he continued working on minerals and the relationship between land use and geology. Since 2006, he held various leadership positions, and his scope and responsibilities have broadened to the delivery of geological information in general.

Michiel will give a broad overview of subsidence in the Netherlands, which started many centuries ago as the unforeseen but inevitable by-product of the Dutch dyking and draining the once active fluvial/coastal sedimentary system they inhabit. In the same area, reclaimed depressions left by centuries of superficial peat mining are so vast that they are not easily recognizable in the current landscape. Coal mining, salt mining and hydrocarbon extraction have resulted in subsidence since the late 19^th, early 20^th and late 20^th century, respectively. The fact the Dutch lowlands are getting lower and lower behind safe walls—a world-famous flood defence system—has hitherto not been very helpful in acknowledging subsidence as problem. However, the mood and debate seem to be changing. After feeling safe for many generations, the prospect of sea-level rise have brought the Dutch in a yet to be determined fight/flight/freeze-mode. It is time to consider our future of our lowlands, not only in terms of final images that are sometimes overly apocalyptic and sometimes wildly optimistic, but also of options and scenarios.

 

Michelle Sneed - U.S. Geological Survey
Thursday 20 April 2023, 09:15-10:00

Michelle Sneed is a hydrologist with the U.S. Geological Survey. She spent 25 years leading land subsidence research in the California Water Science Center and now serves as the Technical Support Coordinator for Groundwater Science in the Office of Quality Assurance. She received her BS and MS degrees in geology from California State University, Sacramento, where she subsequently taught geology classes for 10 years. She has published many studies of land subsidence related to fluid-pressure changes in areas throughout California and other areas in the Western U.S., which often had a focus on subsidence impacts to water-conveyance infrastructure. She integrates various methods of land-surface elevation (and elevation change) measurement, including spirit leveling, Global Navigation Satellite System (GNSS), extensometry, and Interferometric Synthetic Aperture Radar (InSAR) techniques, to leverage the diverse spatial and temporal scales of the datasets. Analyses and simulations have focused on the preconsolidation stress, vertical hydraulic conductivities, and the elastic and inelastic compressibilities (storage) of aquifer-system components based on hydrogeological structure, land-surface elevation changes, and groundwater-level changes.

Land Subsidence in the San Joaquin Valley, California, USA — Past, Present, and Outlook
Land subsidence caused by aquifer-system compaction in the San Joaquin Valley, California, USA, is receiving increased attention from water-science professionals and the media because of recent droughts, rapid subsidence rates, and the passage of California’s Sustainable Groundwater Management Act. The compaction of aquifer systems caused by excessive groundwater pumping is by far the single largest cause of subsidence in California, and subsidence in the San Joaquin Valley has been identified as the single largest human alteration of the Earth’s surface topography. The talk will include discussions of subsidence processes, measurements, analyses, and impacts in the San Joaquin Valley, as well as implications from the historic passage of the first California Law to help protect groundwater.