Methods for monitoring land subsidence and earth fissures in the Western USA
Other literature type
Fergason, K. C.
Rucker, M. L.
Panda, B. B.
Depletion of groundwater resources in many deep alluvial basin aquifers in
the Western USA is causing land subsidence, as it does in many regions
worldwide. Land subsidence can severely and adversely impact infrastructure
by changing the ground elevation, ground slope (grade) and through the
development of ground cracks known as earth fissures that can erode into
large gullies. Earth fissures have the potential to compromise the
foundations of dams, levees, and other infrastructure and cause failure.
Subsequent to an evaluation of the overall subsidence experienced in the
vicinity of subsidence-impacted infrastructure, a detailed investigation to
search for earth fissures, and design and/or mitigation of potentially
effected infrastructure, a focused monitoring system should be designed and
implemented. Its purpose is to provide data, and ultimately knowledge, to
reduce the potential adverse impacts of land subsidence and earth fissure
development to the pertinent infrastructure. This risk reduction is realized
by quantifying the rate and distribution of ground deformation, and to detect
ground rupture if it occurs, in the vicinity of the infrastructure.
The authors have successfully designed and implemented monitoring systems
capable of quantifying rates and distributions of ground subsidence and
detection of ground rupture at multiple locations throughout the Western USA
for several types of infrastructure including dams, levees, channels, basins,
roadways, and mining facilities. Effective subsidence and earth fissure
monitoring requires understanding and quantification of historic subsidence,
estimation of potential future subsidence, delineation of the risk for earth
fissures that could impact infrastructure, and motivation and resources to
continue monitoring through time. A successful monitoring system provides the
means to measure ground deformation, grade changes, displacement, and
anticipate and assess the potential for earth fissuring. Employing multiple
methods, a monitoring strategy utilizes an integrated approach, including
both regional and local measurements.
Various methods implemented include conventional practices and proven,
instrumented in-ground sensing systems. The conventional techniques include
repeat optical levelling and global positioning system (GPS) surveys, ground
reconnaissance, photo-geological analysis, groundwater monitoring, and
tape-extensometers. Advanced techniques include the processing and
interpretation of differential interferograms of repeat-pass, satellite-based
synthetic aperture radar data (InSAR), borehole tiltmeters, microseismic
arrays, excavation of monitoring trenches, and time-domain reflectometry