NEWS NOTES ON SUSTAINABLE WATER RESOURCES  New Orleans Subsidence  https://www.nasa.gov/feature/jpl/new-study-maps-rate-of-new-orleans...

NEWS NOTES ON SUSTAINABLE WATER RESOURCES  New Orleans Subsidence  https://www.nasa.gov/feature/jpl/new-study-maps-rate-of-new-orleans-sinking ; The recent tropical storm conditions that caused problems in New Orleans are not a new phenomenon. Research done earlier by NASA delineates problems that continue to beset the region. A summary of the study follows.“New Orleans and surrounding areas continue to sink at highly variable rates due to a combination of natural geologic and human-induced processes, finds a  NASA/university study using NASA airborne radar.“The observed rates of sinking, otherwise known as subsidence, were generally consistent with, but somewhat higher than, previous studies conducted using different radar data. “While the study cites many contributing factors for the regional subsidence, the primary contributors were found to be groundwater pumping and dewatering (surface water pumping to lower the water table, which prevents standing water and soggy ground).“To fully and accurately measure and predict future subsidence in and around New Orleans, it’s necessary to better understand the various natural and human-produced processes contributing to the sinking. Those include withdrawal of water, oil and gas; compaction of shallow sediments; faulting; sinking of Earth’s crust from the weight of deposited sediments; and ongoing vertical movement of land covered by glaciers during the last ice age. The comprehensive subsidence maps produced by this study, with their improved spatial resolution, help scientists differentiate these processes.“The maps were created using data from NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), which uses a technique known as interferometric synthetic aperture radar (InSAR). InSAR compares radar images of Earth’s surface over time to map surface deformation with centimeter-scale precision. It measures total surface elevation changes from all sources -- human and natural, deep seated and shallow. Its data must be carefully interpreted to disentangle these phenomena, which operate at different time and space scales. UAVSAR’s spatial resolution makes it ideal for measuring subsidence in New Orleans, where human-produced subsidence can be large and is often localized.“In addition to the UAVSAR data, researchers from the Center for GeoInformatics (C4G) at Louisiana State University provided up-to-date GPS positioning information for industrial and urban locations within southeast Louisiana. This information helped establish the rate of ground movement at these specific points. C4G maintains the most comprehensive network of GPS reference stations in the state. The Louisiana network consists of more than 50 Continuously Operating Reference Stations, or CORS sites, which acquire the horizontal and vertical coordinates at each station every second of every day. The CORS sites are part of the National Geodetic Survey network.  “The study is published in the Journal of Geophysical Research: Solid Earth.”  The complexity of the situation is illustrated by earlier work done by the USGS. That can be found here: https://pubs.usgs.gov/of/2000/0132/report.pdf ; “The Mississippi River delta plain is subject to the highest rate of relative sea-level rise (3ft per century) of any region in the Nation largely due to rapid geologic subsidence. Subsidence impacts the socio-economic infrastructure of southeastern Louisiana placing the communities and infrastructure at risk of being inundated by the rising sea.  “Current pressures for balanced land and water management and concerns about recovery from natural disasters and protection of environmental quality demand a new role for scientific information. Interdisciplinary research and information derived from earth, life, and social science data can contribute to both policy analysis and decision making. However, there are often no clear and unequivocal answers to land use and environmental issues, owing both to the uncertainties inherent in the scientific information and the need to consider economic, political, social, and aesthetic values.   “Most scientific information is not in a form readily usable by non-scientists. Applications require adapting scientific information to a decision-oriented framework. An objective of this study is to provide the necessary components of an integrated assessment of southeastern Louisiana these are: (1) identify physical processes; (2) develop a map-based linkage of the human-physical environmental interface; (3) develop a conceptual model for decision making that recognizes uncertainty; and (4) develop a management model that incorporates an estimation of the net benefits to society.”