This study aimed to provide relevant knowledge about the dynamics of the hydrological parameters in the river-estuary continuum of the Wouri-Nkam river estuary for a sustainable management program. The hydrological parameters were recorded in eleven stations spanned out on the basis of population density and human activities. Water quality parameters (Temperature, salinity, dissolved oxygen, pH, Total dissolved solutes, Redox potential and conductivity) were collected in subsurface water using a multiple parameter. Surface currents and morphometric (depth and width) parameters were recorded using a drifter, sonar depth and GPS. The field measurements took placed between 18/05/2019 to 08/09/2020 and were divided into six (06) cruises. The data were later subjected to an analysis of variance (ANOVA) and Principle Component Analysis using XLSTAT 2017 (2.7 version) software. Results obtained revealed that, the water quality parameters were spatially more stable not signficant at (df = 9, p < 0.05) with a relatively low temperature (25.5˚C -27˚C) during the wet period. The limit of the frontal zone extended to S5 (Bonalokan, 8.25 km from S1) during the snapshot of the dry period, spring phase and flood tide conditions. Inversely, during wet period, this extension reduced to S1 (Bridge) and relatively increases slightly to S3 (Bonangang) during the neap phase and ebb tides of this season. This result revealed a change in the axial gradient of about eight (08)

Sone Essoh, W.; Onguene, R.; Ndongo, B.; Nshagali, G.; Colmet-Daage, A.; Marie, G.; Iroume, J.; Stieglitz, T.; Besck, F.; Efole Ewoukem, T.; Tomedi Eyango, M.; Etame, J., and Braun, J.J., 2023. Using GIS and multicriteria analysis to map flood risk areas of the Tongo Bassa River Basin (Douala, Cameroon). Journal of Coastal Research, 39(3), 531–543. Charlotte (North Carolina), ISSN 0749-0208.The present study aimed to map the areas at risk of flooding in the Tongo Bassa watershed (42 km2) located in the heart of the Cameroonian economic capital (Douala) in the tropical zone of Central Africa, more precisely in the Wouri Estuary, at the bottom of the Gulf of Guinea. Like most of the world's major cities, Douala is subject to floods. The methodological approach was to identify the flooding risk determinants in the area from an extensive literature review and field surveys and then analyze these factors and map areas at risk of flooding using the analytical hierarchy process approach coupled with the GIS environment. The results revealed that four parameters of the natural environment (elevation, drainage density, distance to the river, and land cover) were the factors that mainly influenced the phenomenon of flooding in the region. Three major classes of flood risk were highlighted: low risk, medium risk, and high risk. To validate the effectiveness of the flood risk map obtained, the flood points collected in the field were cross-checked for ground truth after a flood occurred in the watershed. This cross-check between the resulting map and the flood points using GIS tools showed a good representation of the flooded area. This result is quite interesting because the areas where the risk of flooding is high are consistent with those where flooding is most frequent. The presented results constitute a basic decision support tool for the management of flood zones by the public authorities and the decentralized territorial communities of the city of Douala.

The aim of this study was to highlight the effect of tide on the variation of the physicochemical parameter in the Kienké estuary. Six (06) environmental variables were monitored at nine (09) stations with the time step of one hour from 7 am to 7 pm on 4 th August 2019. The hovmuller analysis showed that salinity, conductivity, total dissolved solids, and pH values increased during the flood phase and decreased during the ebb phase while oxygen concentration decreased during the flood and increased during the ebb phase. The stratification parameter has shown that the influx of seawater during high tide shifts the Kienké estuary from a well-mixed to a partially mixed environment.

Aims:The research work is aimed at evaluating the land base source of River pollution using a waste characterisation study in the Yabassi municipality in order to design strategies for mitigating pollution of the Nkam River. Study Design: A household survey involving random sampling of 45 households in three residential neighbourhoods (Banya, Ndogbele and the Administrative Centre) to determine their socioeconomic status. Of a total of 117 participants, 45 (44.0%) lived in Banya, 30 (34.2%) in Ndogbele and 25 (24.8%) in the Administrative Centre. Place and Duration of Study: Yabassi Municipality involving three residential neighbourhoods (Banya, Ndogbele and the Administrative Centre) between February and July 2017. Methodology: Household surveys involving three residential neighbourhoods (Banya, Ndogbele and the Administrative Centre) in the Yabassi municipality was carried out to identify individuals belonging to the three socio-economic income classes (low, medium and high). A questionnaire was administered to 117 persons randomly selected from 45 households i.e. 15 from each of the three residential neighbourhoods to participate in a two weeks waste characterisation study. The

The recently constructed Besseke’s flood drain is always filled with water due to individual or combined effect of the tide, urbanization drainage, underground plumes and precipitations runoffs. This study focused on the analysis of small scales dynamics inferred from short term tidal measurements to mitigate the daily flooding in the Besseke’s flood drain. The methodology used is based on field measurements observation. The sampling of water level was conducted during two (02) different tidal regimes in May 2019. The volume of brackish water moving in and out of the Besseke’s flood drain was calculated using the formula of O’Brien. The results showed that Spring conditions had greater amplitudes than Neap tide conditions. During Spring tides, the tidal prism that passed in the midsection of the Besseke’s flood drain (S4) was 3.5 × 101 m3. This means that only a negligible amount of the incoming brackish water reaches the Besseke’s flood drain, amplifies and causes the daily flooding. The unexpected stronger amplitudes and dynamics observed in S4 could be due to its sub estuary nature. Furthermore, the percentage composition of water in this section, showed that the fraction of brackish water changes from 85.7% during Spring tide to 77.8% in the Neap tide conditions. The overall spatial evolution revealed that, the trend in tidal prism (during Spring conditions) was (S0) > (S2) > (S1) > (S3) > (S4) with corresponding values of 2.1 × 104, 1.3 ×104, 1.0 × 104, 2.5 × 102 and 3.5 × 101 m3 respectively. Finally, Tidal prism and Cross-sectional area showed a perfect correlation (r2 = 0.96). The best fitted Cross-sectional area-Tidal prism relationship was obtained in S3 (Market) during Spring tide condition.