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Assessment of Relative Risk of Seawater Intrusion Mechanisms in the Coastal Plains of the Limpopo River Basin, Mozambique
  • Gabriella Zuccolotto,
  • David Murray Kahler
Gabriella Zuccolotto
University of Pittsburgh
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David Murray Kahler
Duquesne University

Corresponding Author:david.m.kahler@gmail.com

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Seawater inundation was reported in the Limpopo River near the mouth at Xai-Xai, Mozambique. Local authorities identified a decrease in river flow as the cause of seawater inundation. We examined the potential of land subsidence in the relative risk of seawater inundation. Land subsidence has been identified as a risk to urban centers; however, we focused on the risk to the surrounding agricultural region. We used Sentinel-1 interferometric synthetic aperture radar (InSAR) with small baseline subset (SBAS) method to determine the rate of land subsidence throughout the agricultural-rich river valley surrounding Xai-Xai, Mozambique. InSAR presents a useful tool to assess land deformation; however, the signal decorrelated in the wet season, which limited our analysis to the dry season. Land subsidence may be due to groundwater abstraction, erosion without sediment transport and replenishment or other alteration of the surface, or tectonic movement. We estimated that the coastal region, which is largely agricultural, has subsided at an average rate of 13 mm/a from 2017 to 2022 and as much as 30 mm/a. This suggests that land subsidence contributes to the relative risk of seawater inundation on the same scale as the decrease in river discharge. Seawater inundation presents a threat to economic growth and food security in the region.
01 Apr 2023Submitted to ESS Open Archive
04 Apr 2023Published in ESS Open Archive