Potential of video cameras in assessing event and seasonal coastline behaviour: Grand Popo, Benin (Gulf of Guinea)

In this study, we explore the potential of a nearshore video system to obtain a long-term estimation of coastal variables (shoreline, beach slope, sea level elevation and wave forcing) at Grand Popo beach, Benin, West Africa, from March 2013 to February 2015. We first present a validation of the video system with field data over a 10-day experiment conducted on Grand Popo beach in 2014. Secondly, 2-years daily and monthly timeseries are extracted and their variability is described as a function of regional forcing and climatic modes. All variables show large monthly variability. The longshore sediment transport estimated locally from video is in agreement with that derived from Era-Interim wave data re-analyses. Results show that the shoreline responds predominantly to tides at the event scale and to waves. Overall, this study suggests that video stations are efficient tools to monitor coastal processes over the long term, in complement with other conventional approaches. Although no clear conclusions can be drawn on inter-annual variability, the results show that it is important to build up extended coastal observation networks to address coastline changes over a wide range of scales.