Addressing Subsidence in Bangkok, Thailand and Houston, Texas: Scientific Comparisons and Data-Driven Groundwater Policies for Coastal Land-Surface Subsidence

Abstract

Land subsidence in coastal regions of the world is a common occurrence. In large metropolitan areas such as Bangkok, Thailand, and Houston, USA, land subsidence occurs as a direct result of groundwater withdrawals for municipal supply, industrial use, and irrigation that depressurize and dewater aquifers. The impacts of subsidence are exacerbated in both cities because of flat, low-lying topography and the presence of unconsolidated clay layers that exist in the aquifer sediments and are prone to compaction. The compaction of these sediments leads to land-surface subsidence, which increases flooding risk and leads to infrastructure and engineering problems. The aquifers in Bangkok are divided into 8 water-bearing units with the Upper Bangkok aquifer (20–30 m thick) being the principal aquifer. In the Houston region, two primary aquifers, the Chicot and Evangeline aquifers (200 and 500 m thick, respectively), comprise the Gulf Coast aquifer system and are susceptible to compaction, with 111.13 cm (1974–2017) and 47.98 cm (1973–2017) of cumulative compaction recorded at the Addicks and Seabrook extensometers, respectively. In both cases, compaction in the aquifer-systems has occurred for decades as groundwater levels declined. Scientific advancements in data collection, analysis, and communication have helped policymakers implement various management strategies with groundwater use becoming even more crucial as population increases. Both the Thailand Department of Groundwater Resources and U.S. Geological Survey have more than 40 years of subsidence data to compare how data is collected and analyzed within their respective areas. This paper will illustrate scientific efforts to study subsidence in Bangkok and Houston by correlating data of long-term groundwater withdrawals and cumulative sediment compaction and then comparing resulting policy changes.