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<p>Floods represent the most prevalent natural disaster globally, inflicting significant physical and economic harm on coastal megacities such as Douala. The objective of the current work is to provide key insights into the spatial dynamics of water levels and, consequently, impacts on flood-prone areas, which are critical for the implementation of early warning systems and other effective interventions to mitigate flood risks in the city of Douala. Field measurements from the flood event on August 21,&#xa0;2020, were utilized to analyse the hydrological changes in the Wouri-Nkam River Estuary. The findings revealed two distinct dynamics: the lower segment (Douala harbour) displays a semi-diurnal tidal signal characterized by a constant flood-ebb oscillation, while the upper riverine section (Bona’Anja siga Bonjo hamlet) demonstrates an eroding semi-diurnal nature. The flood severity index (FSI) indicated the highest values in the upper riverine section. The maximum FSI value was recorded near Bonagang (FSI = 3.50), followed by Bona’Anja (FSI = 2.087). In contrast, the minimum value (FSI = 1) was observed at the Douala port (estuarine end). The estuarine side exhibited minimal tidal attenuation rates, ranging from 9 to 13%, whereas the riverine side experienced a total loss of the tidal signal, resulting in a 100% reduction. This study finds that the upper segment of the estuary may be more susceptible to flooding due to the interplay of pluvial and fluvial flooding. The presence of mangrove stands and the influence of spring tides hinder the free flow of water between sections, thereby increasing water accumulation in the upper area. Therefore, it is essential to focus attention on this section rather than on the lower estuarine section.</p>

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Change in Hydrological Signature of Tropical River-Estuaries During Extreme Flood Conditions: A Case Study of the Wouri-Nkam River Estuary (Cameroon) During the August 2020 Flood Event

  • 期刊论文

  • 发表日期：

    2025年8月11日

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  • Felix Besack,
  • Landry Essome Mbang,
  • Josué Manga Tchogom,
  • Gordon Ajonina,
  • Seth Rodrigue Ebonji,
  • Raphael Onguene,
  • Minette Eyango Tomedi,
  • Olusegun Dada

摘要

Floods represent the most prevalent natural disaster globally, inflicting significant physical and economic harm on coastal megacities such as Douala. The objective of the current work is to provide key insights into the spatial dynamics of water levels and, consequently, impacts on flood-prone areas, which are critical for the implementation of early warning systems and other effective interventions to mitigate flood risks in the city of Douala. Field measurements from the flood event on August 21, 2020, were utilized to analyse the hydrological changes in the Wouri-Nkam River Estuary. The findings revealed two distinct dynamics: the lower segment (Douala harbour) displays a semi-diurnal tidal signal characterized by a constant flood-ebb oscillation, while the upper riverine section (Bona’Anja siga Bonjo hamlet) demonstrates an eroding semi-diurnal nature. The flood severity index (FSI) indicated the highest values in the upper riverine section. The maximum FSI value was recorded near Bonagang (FSI = 3.50), followed by Bona’Anja (FSI = 2.087). In contrast, the minimum value (FSI = 1) was observed at the Douala port (estuarine end). The estuarine side exhibited minimal tidal attenuation rates, ranging from 9 to 13%, whereas the riverine side experienced a total loss of the tidal signal, resulting in a 100% reduction. This study finds that the upper segment of the estuary may be more susceptible to flooding due to the interplay of pluvial and fluvial flooding. The presence of mangrove stands and the influence of spring tides hinder the free flow of water between sections, thereby increasing water accumulation in the upper area. Therefore, it is essential to focus attention on this section rather than on the lower estuarine section.