Rainfall variability and floods occurrence in the city of Bamenda (Northwest of Cameroon)

Abstract

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.

Spatio-Temporal Hydro-Meteorological Variability Challenges on Floodplain Wetland Ecosystem Sustainability Downstream of Hydroelectric Dams, Niger State, Nigeria

“…Hence, these higher peak values could be a prime factor responsible the recurring flood upstream of River Kaduna with devastating impact on Kaduna and that had IRMI <10 (Figures 2 and 3). This is in agreement with Frederic and Mesmin [13] that concludes that, rainfall reinforces the risk of flooding by increasing flood water and increasing the vulnerability of populations. The 1991-1999 IRMI values expect 1999 rose gradually between pentad 37 and 54 th as 1991was characterized with fluctuations due to breaks in rainfall thereby minimizing runoff and subsequently inflow (Figure 2c-d).…”

“…Consequently, the dominancy and consistency in the moderate and high discharge levels are indicator for increase flooding events across downstream community as low-level discharge have continued to give way for moderate and high discharge in recent times. This affirmed by Frederic and Mesmin [13] and Haider [25] that there is no doubt that climate risks in recent years have experienced significant strengthening. In addition, the positive trend of the variables reveals increase flood potential which are threat to food, socio-economic, national and regional security as large proportion of populace depends on this ecosystem for livelihood.…”

“…The steady rise of the IRMI values from pentad 40 -56 th without remarkable fluctuations is an indication of high rainfall which is devoid of break and is major factor that aggravates 2012 flooding events across the country. Similarly, Frederic and Mesmin[13] concluded that gradual increase in annual rainfall amounts especially in the last two decades is the cause of increased flood water heights. The 2011, 2014 and 2015 values rises gradually while 2013 value is generally below 10 an indication of no flood condition throughout the growing season.3.1.3.…”