This study is based on analysis of rainfall data from 1951-2010 collected at the climatic station of Bamenda. We also use the results of a questionnaire survey applied to 172 households in at-risk neighborhoods. The inventory of some cases of flooding that occurred in the city of Bamenda was done through focus groups. The appreciation of the socio-economic and demographic environment is based on surveys among Cameroonian Households by the National Institute of Statistics (NIS) and General Census of Population and Housing. Statistical examination revealed that annual rainfall in the city of Bamenda experienced a break in 1958. This break buckled the wettest decade of the series. After three decades of worsening, rainfall is experiencing rising since early 1990. The average profile of the annual distribution of rainfall shows a concentration of over 53% in 03 months (July, August and September). During these three months, the rivers of the city know their flood flows and populations in the valleys are affected. The analysis of the annual number of rainy days shows a downward trend and an increase of extreme rainfall event frequency (≥50mm in 24h). It is also apparent that more and more years are experiencing erratic distribution of their precipitation. Then, the perception of people is significantly reduced. Subsistence activities are also affected and development is facing new subtleties. In conclusion, the rainfall experienced strong variability in the city of Bamenda. This situation reinforces the risk of flooding by increasing flood water and increasing the vulnerability of populations.

Cet article examine les facteurs de production des risques dits « naturels » dans les grandes villes du Cameroun. D’une approche historique, il ressort que l’établissement d’agglomérations dans des sites d’aménagement difficile est à la base du problème. Le manque de ressources ainsi que la forte croissance démographique qui caractérisent les pays les moins avancés (PMA) en général et le Cameroun en particulier sont du point de vue anthropique les causes de la forte sensibilité aux risques naturels. Il se pose aussi le problème de l’ambiguïté du système foncier qui n’aide pas à la maîtrise de l’espace. L’incapacité des autorités et de la protection civile à gérer l’espace urbain consolide la vulnérabilité. Les changements climatiques diminuent la perception et l’acceptation des risques par les populations et augmentent leur fréquence.

Le système Chari-Logone est le principal pourvoyeur d'eau du lac Tchad. Il s'agit également du principal cours d'eau drainant l'Extrême-Nord du Cameroun. À l'image des autres parties du bassin versant, cette région a connu plusieurs inondations catastrophiques au cours des trois dernières décennies. Cet article examine la dynamique des extrêmes hydrologiques, et donc des sècheresses et des inondations, du Logone et du Chari aux stations de Bongor et de N'Djamena, en prenant en compte le contexte des changements climatiques. Les analyses s'appuient sur les données journalières maximales (Qmax) et minimales (Qmin) de la période 1955-2016. Les logiciels XLStat et KhronoStat ont permis de calculer un ensemble d'indices (indice d'irrégularité, coefficient de tarissement, coefficient A de MYER). Ces logiciels ont aussi été utilisés pour déterminer les tendances dans l'évolution temporelle des données.Les débits du Logone et du Chari permettent de distinguer les conditions hydro-climatiques qui se sont succédé dans la zone sahélienne du Cameroun sur la période d'étude. Les Qmax ont subi une rupture en 1971-72 à Bongor et en 1972-73 à N'Djamena. Ces ruptures témoignent du passage de conditions humides à une sècheresse marquée. À Bongor, les Qmin ont subi trois ruptures successives, en 1971-72, 1998-99 et 2010-11. À N'Djamena, en revanche, une seule rupture s'est manifestée, en 1981-82, avec une baisse des valeurs de 55 %. À partir de 2000, les conditions deviennent particulièrement contrastées, surtout à Bongor, avec une alternance d'années aux écoulements très différents.En moyenne, le coefficient A de MYER est de 6,5 à Bongor et de 3,2 à N'Djamena. Cela traduit une faible puissance des crues. La valeur annuelle du rapport Qmax/Qmin a baissé progressivement à Bongor, alors qu'elle a augmenté à N'Djamena. Le coefficient de tarissement de MAILLET est faible en général (0,019/jour en moyenne) ; 6 mois peuvent s'écouler entre la survenue de Qmax et celle de Qmin.Seulement 23 % des inondations catastrophiques relevées dans le secteur d'étude, se sont produites au cours d'années humides. Cela témoigne du rôle important que jouent d'autres facteurs, comme la distribution spatiale des pluies.

Cameroon territory is experiencing significant land use and land cover (LULC) changes since its independence in 1960. But the main relevant impacts are recorded since 1990 due to intensification of agricultural activities and urbanization. LULC effects and dynamics vary from one region to another according to the type of vegetation cover and activities. Using remote sensing, GIS and subsidiary data, this paper attempted to model the land use and land cover (LULC) change in the Centre Region of Cameroon that host Yaoundé metropolis. The rapid expansion of the city of Yaoundé drives to the land conversion with farmland intensification and forest depletion accelerating the rate at which land use and land cover (LULC) transformations take place. This study aims at assessing the impacts of both agriculture and urbanization on the LULC change in the Centre Region of Cameroon. A detailed LULC map from MAPBOX high resolution images and three LULC maps were produced from Landsat TM-OLI images (1984-2015). A maximum likelihood classification techniques using ERDAS Imagine, showed forest decline with a total loss of 54% in thirty years. Also, Landsat and MAPBOX images to which we added 1951 aerial photograph and SPOT 6 (2006) were used to analyse urban growth in the city of Yaoundé. The results show a remarkable urban spatial spread of the metropolis between 1951 and 2015, with a peak in 2000. Images processing enabled us to analyse the long term dynamics of LULC change since the 1950s in this Region using ArcGIS & QGIS software’s. Based on this dynamic, a LULC projection map was produced using Markov model on IDRISI Selva, demonstrating the decrease of the dense forest (45% in 2015 to 0.25% in 2050). It was estimated that by 2050, the entire dense forest can be depleted if nothing is done, while only 12.67% of the secondary forest would remain in the Region. Such a projected map is very useful to decision makers for council development and urban planning. This effective forest depletion ties with the hypothesis that urbanization of Yaoundé and its secondary surrounding satellite cities (within a radius of 30-100km) is a veritable driving force of deforestation.

This study examines the atmospheric mechanisms behind the extreme rainfall event of August 2024 in the northern Chad, and their devastating socio-economic impacts. Analysis of the hydro-climatic regime over the region reveals a major structural transition marked by a statistical tipping point in 2003, shifting from historical aridity to a phase of intensified rainfall that culminated in the record high of August 2024. Our analysis of lower-tropospheric convergence, specific humidity, vertical velocity (ω), and moist static energy (MSE) reveals a major shift from the typical West African monsoon regime. In August 2024, the Intertropical Front (ITF) shifted abnormally northward, reaching 20–22° N, which allows moist moisture air to penetrate deep into the Saharan zone. This shift was driven by strengthened convergence at 850 hPa and a significant increase in low-level humidity. Furthermore, negative ω anomalies throughout the troposphere indicate a northward extension of the monsoon's upward branch. Strong positive MSE anomalies over desert regions further highlight a thermodynamic enrichment of the atmospheric column. Together, these signals point to a highly effective dynamic-thermodynamic coupling that fueled intense convective systems. Ultimately, the synchronization between these atmospheric condition and the synoptic forcing of African easterly waves generated local rainfall anomalies exceeding 100 %, redefining the hydrological balance of the Lake Chad basin between aquifer recharge and increased risks of flash flooding. This hydro-climatic shift had immediate and devastating socio-economic impacts: the resulting flooding affected nearly 20,000 people across four desert provinces in Chad. In Tibesti alone, sixty lives were lost due to drowning or building collapses, alongside significant losses of livestock and infrastructure.