Monitoring Cross-shore Intertidal Beach Dynamics using Oblique Time-lapse Photography

Guisado-Pintado, E. and Jackson, D.W.T., 2020. Monitoring cross-shore intertidal beach dynamics using oblique time-lapse photography. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1106-1110. Coconut Creek (Florida), ISSN 0749-0208. Regular, long-term coastal monitoring of sandy beaches using cross-shore profiling provides important insights into longer term morphodynamic behaviour which cannot be achieved from infrequent, event-led measurements. The need for rapid survey excursions to capture contemporary morphological impacts from storms and dynamic bedforms moving across intertidal regions has challenged traditional (and even modern) monitoring techniques. The use of video/stills cameras in coastal areas is represented by some well-known precedents such as the Argos camera system and more recently initiatives such as CoastSnap. This paper presents a low-cost, innovative method for the acquisition of regular beach images using a fixed, time-lapse camera system at a beach-dune setting in north west Ireland. The camera was located in an oblique position on high ground overlooking the study site, with a field of view of 59° and set to acquire images every 30 minutes. Camera images were calibrated using Ground Control Points (GCPs), acquired at regular geo-located intervals along intertidal profile lengths. A scaling factor was calculated using these GCPs to identify the average distance of each pixel on the ground and converted into real-world distance. The study spans a two-month period extracting from the imagery, lateral onshore intertidal bar migration, which allowed detailed gross movement information to be acquired. The imaging method is a valuable technique for visualizing regular monitoring of beaches during high-energy wave events.