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<p>Rapid urbanization in the Ogun River Basin has substantially altered natural land cover and intensified floodplain encroachment, yet most existing studies remain largely descriptive and fail to quantify future flood exposure linked to land transformation. This study integrates multi-temporal remote sensing, Height Above Nearest Drainage (HAND) modelling, and Cellular Automata–Markov (CA-Markov) simulation to assess historical (1984–2024) and projected (2044–2064) land use/land cover (LULC) dynamics and their implications for flood vulnerability. Landsat imagery was classified using a Random Forest supervised algorithm, achieving overall accuracies between 86.3% and 92.7% with Kappa coefficients exceeding 0.83. Flood-prone zones were delineated using HAND derived from 30&#xa0;m SRTM DEM and validated against historical flood records, yielding an accuracy of 0.75 and ROC-AUC of 0.73. Results reveal that built-up areas expanded from 1.58% (373.9&#xa0;km²) in 1984 to 4.87% (1,151.5&#xa0;km²) in 2024, with projections indicating a further increase to 15.76% (3,729.8&#xa0;km²) by 2064. Approximately 64.7% of the basin lies within high and very-high flood hazard zones, predominantly across rapidly urbanizing southern LGAs. Urban land within flood-prone areas increased by over 200% between 1984 and 2024 (from 128.4&#xa0;km² to 400.2&#xa0;km²) and is projected to reach about 1,245&#xa0;km² by 2064. Water bodies within floodplains are also expected to expand from 251.6&#xa0;km² in 2024 to 354.2&#xa0;km² by 2064, reflecting increasing hydrological alteration. The findings demonstrate that unregulated urban expansion is the dominant driver of rising flood exposure in the basin. The integrated HAND–CA-Markov framework offers a robust, transferable tool for flood-risk-informed spatial planning, enabling policymakers to identify priority zones for development control, floodplain protection, and climate adaptation. This evidence directly supports sustainable urban growth, disaster risk reduction, and ecosystem conservation strategies aligned with the SDGs and the Sendai Framework.</p>

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Urbanization driven land cover change and floodplain transformation in the Ogun River Basin using HAND and CA-Markov models

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月7日

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  • Akinola Adesuji Komolafe,
  • Adedoyin Benson Adeyemi,
  • Christy Ayobami Babalola,
  • Etari Joy Ebijuoworih,
  • Saidi Olalekan Lawal,
  • Oluwaseun Bamidele Odedeyi,
  • Samuel Olumide Akande,
  • Suleiman Abdul-Azeez Adegboyega

摘要

Rapid urbanization in the Ogun River Basin has substantially altered natural land cover and intensified floodplain encroachment, yet most existing studies remain largely descriptive and fail to quantify future flood exposure linked to land transformation. This study integrates multi-temporal remote sensing, Height Above Nearest Drainage (HAND) modelling, and Cellular Automata–Markov (CA-Markov) simulation to assess historical (1984–2024) and projected (2044–2064) land use/land cover (LULC) dynamics and their implications for flood vulnerability. Landsat imagery was classified using a Random Forest supervised algorithm, achieving overall accuracies between 86.3% and 92.7% with Kappa coefficients exceeding 0.83. Flood-prone zones were delineated using HAND derived from 30 m SRTM DEM and validated against historical flood records, yielding an accuracy of 0.75 and ROC-AUC of 0.73. Results reveal that built-up areas expanded from 1.58% (373.9 km²) in 1984 to 4.87% (1,151.5 km²) in 2024, with projections indicating a further increase to 15.76% (3,729.8 km²) by 2064. Approximately 64.7% of the basin lies within high and very-high flood hazard zones, predominantly across rapidly urbanizing southern LGAs. Urban land within flood-prone areas increased by over 200% between 1984 and 2024 (from 128.4 km² to 400.2 km²) and is projected to reach about 1,245 km² by 2064. Water bodies within floodplains are also expected to expand from 251.6 km² in 2024 to 354.2 km² by 2064, reflecting increasing hydrological alteration. The findings demonstrate that unregulated urban expansion is the dominant driver of rising flood exposure in the basin. The integrated HAND–CA-Markov framework offers a robust, transferable tool for flood-risk-informed spatial planning, enabling policymakers to identify priority zones for development control, floodplain protection, and climate adaptation. This evidence directly supports sustainable urban growth, disaster risk reduction, and ecosystem conservation strategies aligned with the SDGs and the Sendai Framework.