Global subsidence of river deltas

Area of Science:

• Earth and Environmental Science
• Geophysics
• Remote Sensing

Background:

• River deltas are critical hubs for human populations, economies, and ecosystems.
• Rising sea levels and land subsidence pose significant threats, including flooding, land loss, and salinization.
• Accurate, high-resolution data on delta-wide subsidence is crucial for vulnerability assessments but is currently lacking.

Purpose of the Study:

• To present a novel dataset of spatially variable surface-elevation changes across 40 global deltas.
• To quantify delta surface-elevation loss and assess the global prevalence and severity of subsidence.
• To identify and analyze the anthropogenic drivers influencing vertical land motion in deltas.

Main Methods:

• Utilized interferometric synthetic aperture radar (InSAR) to measure surface-elevation changes.
• Analyzed data from 40 deltas worldwide to map subsidence patterns.
• Investigated the influence of groundwater storage, sediment flux, and urban expansion on land subsidence.

Main Results:

• Quantified significant surface-elevation loss across the studied deltas, revealing widespread and severe subsidence.
• Identified groundwater storage as the dominant driver of vertical land motion in 10 deltas.
• Found that contemporary subsidence is the primary driver of relative sea-level rise in most deltas, exceeding global sea-level rise projections for the 21st century.

Conclusions:

• Subsidence is a critical, immediate threat to deltas globally, often surpassing the impact of global sea-level rise.
• Human activities, particularly groundwater extraction, significantly contribute to delta subsidence.
• Targeted interventions addressing subsidence are essential for delta resilience, complementing broader climate change adaptation strategies.