Photogrammetric assessment of shoreline retreat in North Africa: Anthropogenic and natural drivers

Oula Amrouni, Abderraouf Hzami, Essam Heggy

Research output: Contribution to journalArticle

Abstract

Shoreline retreat along extended semi-arid areas of North African coasts are indicative of the imbalance of coastal sedimentary processes due to modern abrupt changes in precipitation patterns and urban growth. Monitoring of the diachronic shoreline position and land-use from 1952 to 2018 in the coast of the Hammamet Bay in central-east Tunisia, using both aerial and orbital photogrammetric scenes and the Digital Shoreline Analysis System from 1887 to 2018, suggests shoreline retreat rates ranging from −1.3 to −5.6 m/yr. Such rates are abnormal when compared to the average of −0.07 m/yr suggested by global-scale assessment modeling for sandy beach evolution. These abnormal erosions extend over 65 km of sandy beaches, resulting from a severe deficit of sediment transport caused primarily by rapid coastal urban growth that obstructs sediment flow to the shoreline. We suggest that the high retreat rates observed in the low-population period of 1884–1931 originated mainly from storm surges and tsunamis, or potentially subsidence in the coastal substratum. Moreover, our analysis of the salinity of shallow coastal aquifers and land coverage suggests that shoreline retreat coupled with rapid urban growth accelerated seawater intrusion ~5 km inland, causing soil desiccation, the development of salt lakes, and reduction of vegetation coverage by ~18%. These abrupt environmental changes have a severe, adverse impact on crop production and food security in these densely populated and economically important areas across significant parts of the North African coasts, sharing similar key environmental parameters with our study site. We conclude that anthropogenic drivers are the major source of shoreline retreat rather than natural ones.

Original languageEnglish
Pages (from-to)73-92
Number of pages20
JournalISPRS Journal of Photogrammetry and Remote Sensing
Volume157
DOIs
Publication statusPublished - 1 Nov 2019

Fingerprint

Urban growth
shorelines
Coastal zones
shoreline
Beaches
Salt water intrusion
urban growth
coasts
Tsunamis
Sediment transport
Subsidence
beaches
Aquifers
Land use
Crops
Lakes
Erosion
Sediments
coast
Salts

Keywords

  • Change detection
  • Coastal dynamics
  • Land-use and groundwater
  • Littoral sedimentation
  • Seawater intrusion
  • Shoreline retreat

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Computer Science Applications
  • Computers in Earth Sciences

Cite this

Photogrammetric assessment of shoreline retreat in North Africa : Anthropogenic and natural drivers. / Amrouni, Oula; Hzami, Abderraouf; Heggy, Essam.

In: ISPRS Journal of Photogrammetry and Remote Sensing, Vol. 157, 01.11.2019, p. 73-92.

Research output: Contribution to journalArticle

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