Rapid Land Subsidence Associated with Severe Drought: A Case Study in the Houston Area, Texas

Date

2015-05

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Abstract

This study investigated the drought-induced subsidence which occurred in 2011 in the Houston area, Southeast Texas. The Houston area has been suffering from subsidence for several decades. Groundwater withdrawals have been identified as the primary driver of ground subsidence in the Houston area. According to the Palmer Drought Severity Index (PDSI) of the National Oceanic and Atmospheric Administration (NOAA), 2011 was the driest year between 2004 and 2013 in the Houston area. Coincidently, the damage rates of buried utility pipes associated with ground deformation were tripled in 2011 summer in the Houston area. There has been insufficient study of drought-induced subsidence in the Houston area. A dense Global Positioning System (GPS) Network has been installed in this area for the purpose of tracking subsidence. Many of these GPS stations recorded significant subsidence during 2011. Using various data sets (GPS data, extensometer data, groundwater level data, precipitation data, weather data, and pumpage data), we illustrated the rapid drought-induced subsidence of 2011, and its relation with groundwater withdrawals and groundwater level changes. Yearly subsidence or aquifer compaction rates were obtained from thirteen extensometers and five Continuously Operating Reference Stations (CORS) in the Houston area. GPS raw data (2004-2013) were processed by the Precise Point Positioning (PPP) method employed in the GIPSY-OASIS (V6.3) software package. The PPP solutions within the global reference frame (IGS08) were transformed to a local reference frame, Stable Houston Reference Frame (SHRF). We correlated groundwater level data, precipitation data, weather data, and pumpage data to investigate factors inducing subsidence. Rapid subsidence in 2011 was clearly shown by the above average surface subsidence rates and aquifer compaction rates. Groundwater withdrawals were consequences of decreased precipitation and increased groundwater use in 2011. This study verified that the rapid subsidence in 2011 were induced by groundwater withdrawals. In order to minimize the damage of ground deformation to urban infrastructure during a severe drought season, a strict groundwater regulation is recommended.

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Keywords

Drought-induced subsidence, GPS, Extensometers

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