Nationwide Subsidence in Bahrain Island: Drivers and Implications for Relative Sea-Level Rise

Abstract

The IPCC-AR6 report suggests that the sea-level in the Persian Gulf is expected to rise by 2.1-4.9mm/year by 2100, which is lower than the global projections of 4-14mm/year. However, a central nationwide ground subsidence in Bahrain's low-lying island can aggravate these figures. The island is only 14-kilometers-wide, yet we observe a 7×12-kilometer ground subsidence with vertical rates up to 20mm/year for 2016-2021. To characterize the subsidence, we use the following methods: (i) SBAS-InSAR with 94 and 131 C-band Sentinel-1A orbital radar acquisitions in ascending and descending directions for 2016-2021, respectively, and (ii) Stacking-InSAR with eight L-band ALOS-1-PALSAR acquisitions for 2007-2010 and six ALOS-2-PALSAR-ScanSAR acquisitions for 2016-2021. Although the observed subsidence velocities are non-linear, we estimate a subsidence of up to 1.5-meters by 2100 by extrapolating the average rates. We suggest three causes associated with this subsidence: (i) Exploitation of the Awali oil field, (ii) Local aquifer depletion, and (iii) Subsurface dissolution of anhydrites and chalky-limestones. To assess the potential impact of subsidence on the shoreline, we measure the coastline evolution at three undisturbed beaches on the West-coast from 1985-to-2021, excluding areas that underwent land-reclamation. Using sub-pixel shoreline detection analysis from 308 Sentinel-2 and Landsat (L5, L7, and L8) acquisitions, we observe that the selected shores remain stable. However, observations reveal a shoreline retreat of up to 5m/year on the southwestern coast for 2003-2014. This rate exceeds the modeled rate of 0.85m/year derived solely from local tide gauge sea-level measure. This nationwide subsidence should be considered when forecasting coastal infrastructure-planning in Bahrain. We recommend performing a similar analysis in other lowlying Gulf islands where oil exploitation occurs.

A national-scale assessment of land subsidence in China’s major cities

“…In coastal regions, land subsidence can amplify the risk of inundation caused by rising sea levels ( 47 ). We therefore also projected the proportion of coastal lands that will have a relative elevation lower than sea level under the combined effect of sea-level rise and land subsidence by 2120 ( 22 ).…”

Flood Vulnerability and Resiliency in Coastal Areas Based on Geographic Information Systems (GIS) and Dynamic

“…Major floods occurred in the Mediterranean region and the Ligurian Sea coast, namely Liguria, Tuscany and Sardinia, the effects of weather characteristics, ground effects, and urban expansion in the region resulting in changes in hydro-geomorphological dynamics [2]. These floods are expected to have a higher flood risk when sea level rise occurs [3], [4], his is triggered by rapid economic and social development, which is not accompanied by appropriate and sustainable water management measures [5].…”