The relation between land use and subsidence in the Vietnamese Mekong delta

Abstract

The Vietnamese Mekong delta is subsiding due to a combination of natural and human-induced causes. Over the past several decades, large-scale anthropogenic land-use changes have taken place as a result of increased agricultural production, population growth and urbanization in the delta. Land-use changes can alter the hydrological system or increase loading of the delta surface, amplifying natural subsidence processes or creating new anthropogenic subsidence. The relationships between land use histories and current rates of land subsidence have so far not been studied in the Mekong delta. We quantified InSAR-derived subsidence rates for the various land-use classes and past land-use changes using a new, optical remote sensing-based, 20-year time series of land use. Lowest mean subsidence rates were found for undeveloped land-use classes, like marshland and wetland forest (~6-7mmyr), and highest rates for areas with mixed-crop agriculture and cities (~18-20mmyr). We assessed the relationship strength between current land use, land-use history and subsidence by predicting subsidence rates during the measurement period solely based on land-use history. After initial training of all land-use sequences with InSAR-derived subsidence rates, the land-use-based approach predicted 65-92% of the spatially varying subsidence rates within the measurement error range of the InSAR observations (RMSE=5.8mm). As a result, the spatial patterns visible in the observed subsidence can largely be explained by land use. We discuss in detail the dominant land-use change pathways and their indirect, causal relationships with subsidence. Our spatially explicit evaluation of these pathways provides valuable insights for policymakers concerned with land-use planning in both subsiding and currently stable areas of the Mekong delta and similar systems.

Advances and Practices on the Research, Prevention and Control of Land Subsidence in Coastal Cities

“…The load of new built-up areas and engineering works induce shallow subsurface consolidation, which act also over long periods. Although land subsidence caused by new urbanization significantly threats the safety of population, stability of infrastructures (Tosi et al, 2012;Minderhoud et al, 2018;Wang et al, 2018) and (local) economies, the current state of scientific knowledge is insufficient to cope this critical issue.…”

Towards unraveling total subsidence of a mega-delta – the potential of new PS InSAR data for the Mekong delta

“…One of the large drivers of the subsidence rates presently experienced, was the steady increase in groundwater extraction since the 90's from its thick, locally over 500 m, multi-aquifer system (Minderhoud et al, 2017). As new elevation data revealed that the deltas elevation relative to local sea level is even lower than previously assumed (on average the delta plain is elevated only ∼ 80 cm above local sea level) (Minderhoud et al, 2019), the accelerating subsidence rates strongly increase the vulnerability to sea-level rise-induced flooding, salinization (Eslami et al, 2019), coastal erosion and, ultimately, threaten the livelihood of 18 million delta inhabitants with permanent inundation (Minderhoud et al, 2020).…”

Late Holocene differential subsidence and relative sea level rise in the Tabasco Delta, Mexico

“…In populated deltas, human activities can add to the natural subsidence rates (e.g. Jankowski et al, 2017;Koster et al, 2018;Minderhoud et al, 2018). In addition to these factors, ongoing climate change and associated sea-level rise, and reduced sediment input, substantiate threats of wetland loss and increasing flooding risk, call for monitoring and mitigating subsidence.…”