Current Land Subsidence in the Houston Metropolitan Area, Texas, Derived from

GPS Observations (1993-2012)

Guoquan (Bob) WangUniversity of Houston

With contributions from graduate students: Timothy J. Kearns, Jiangbo Yu, Linqiang Yang, Xueyi Jia, and Jianjun Jiang

Outline• GPS Geodesy Infrastructure in the Houston area Public available GPS stations (Hardware)

Stable Houston Reference Frame (SHRF) (Firmware)

Single-receiver phase ambiguity resolved GIPSY PPP resolution (software)

• Current subsidence mapping (2005-2012)

• Scientific Questions: (1) Is there deep seated (or fault-controlled) subsidence in the Houston area? (2) When will the current subsidence stop?

(USGS, Kasmarek et al., 2009)

(USGS, Coplin and Galloway, 2009)

Historic Subsidence in Houston

3 m within 30 years, 10 cm/year

6 m

USGS

Houston Ship Channel Area

Geodesy Infrastructure: Permanent GPS Stations

Harris-Galveston Subsidence District (70+)

Texas Department of Transportation 15+

City of Houston, others

83 GPS +11 Extensometers

HoustonNet

• NSF MRI: 40 GPS; UH: 10 GPS• Subsidence, faulting, and salt dome uplift• Hurricane intensity forecasting• Civil engineering community---buildings, bridges, dams, sea walls

Geodesy Infrastructure: The Stable Houston Reference Frame

7 years: 2005-2012

Helmert Transformation

Wang et al., 2013

14-Parameter Similarity Transformation

8

(1) Translation along the respective axis (in meters)

(2) Differential Scaling of the respective axis (ppb)

(3) Counterclockwise Rotations (in radians)

14-Transformation Parameters

9

Transformation Parameter UnitIGS08 to SHRFt0 = 2012

IGS08 to NAD83(2011)t0 = 1997*

Tx(t0) cm 0.00000 99.34300Ty(t0) cm 0.00000 -190.33100Tz(t0) cm 0.00000 -52.65500Rx(t0) mas 0.00000 25.91467Ry(t0) mas 0.00000 9.42645Rz(t0) mas 0.00000 11.59935s(t0) ppb 0.00000 1.71504dTx cm/year -1.07250 0.07900dTy cm/year -1.05876 -0.06000dTz cm/year -3.54574 -0.13400dRx mas/year 1.15720 0.06667dRy mas/year -0.93885 -0.75744dRz mas/year -0.33224 -0.05133ds ppb/year 1.37220 -0.10201

       *Pearson and Snay (2013), Table 7

NGS

No-linear subsidence rate

Jersey Village

18 Years

Spatial and temporal variation of subsidence

Ground Deformation at Closely-Spaced (4 km) GPS Sites

Recent Subsidence Mapping (2005-2012)

85 years

6 m

83 GPS +11 Extensometers

Maximum subsidence rate <=2.5 cm/year

< 5 mm/year

7 years: 2005-2012

Aquifer Profile: Chicot + Evangeline

USGS3600 ft

Subsidence---pumping (??%)+ faulting (??%)

Gulf Coast Geology and faults

Ortega, 2013

Subsidence vs. Faulting

Question 1: Is there deep-seated (fault-controlled) subsidence in the Houston-Galveston area?

USGS Borehole Extensometers

13 extensometers at 11 sites 40 years: 1974—2013

USGS

Compaction meter

Addicks Borehole Extensometer (-549 m)

Co-Located GPS and Extensometer Monitoring Site (ADKS)

Wang et al., 2014

+15 years

Wang et al., 2014Journal of Surveying Engineering

Conclusion: The compaction measurements from the long-term extensometers are reliable and the accuracy is about a few millimeters.

Drought of 2005

Drought of 2011

18 years

40 years

Co-located GPS and Extensometer Sites

Conclusion: Compacted aquifers are limited to above -600 m

ADKS(-549 m) NETP (-591 m) LKHU (-661 m)

22 years

Clear Lake—Jonson Space Center Sites

Conclusion: No compaction below -530 m

Clear lake Deep Borehole (-936 m) Clear lake Shallow Borehole (-530 m) Jonson Space Center(-235 m)

50m 2.5 km

37 years

-530 m

Conclusion: Only partial of the Evangeline aquifer had been compacted!

USGS, 2009

Coastal Subsidence: Galveston vs. New Orleans

It appears no considerable tectonic subsidence occurs currently in the Houston-Galveston area.

4 mm/year

UH Coastal Center “Vertical” GPS Array

-30 ft-20 ft-10 ft -1 ft

Borehole GPS

Question 2: When will the subsidence cease?

Conclusion: It took 20 years (1978-1998) to halt the subsidence in the southeast part.

1978-1998

38 years

Conclusion: 2005+20=2025

38 years

Summary

• The ground water and aquifer systems respond slowly to human actions. It took almost two decades (1980s and 1990s) to halt the subsidence in the south-east part of the Houston metropolitan area. Therefore, a long-term perspective is needed to manage groundwater resources and control land subsidence.

• The spatial and temporal variation of subsidence could be very considerable!

subsidence=f(x,y,z t)

• The groundwater regulations implemented by the HGSD are very successful in reducing subsidence rate in the Houston area. Currently, there is no considerable deep-seated or fault-controlled subsidence in the Houston-Galveston area. Current aquifer compaction is limited to about -530m.

Thank you!

Stable: v=0