Identifying Rip Channels Along RK Beach, Visakhapatnam Using Video and Satellite Imagery Analysis

Rip currents are one of the most well-known coastal hazards on the world's beaches. Identification and continuous monitoring of these currents are essential for the safety of beachgoers and prevent the number of drowning cases. Studies on the diversity of rip currents in space and time off the Indian coast are minimal. However, these have long been the subject of research worldwide. Based on the earlier rip current-related works in Visakhapatnam beaches, RK Beach is known for highest recorded number of drowning deaths. Albeit, much attention is not given to monitor and safeguard beachgoers from these furious currents. In this work, a preliminary experimental study has been initiated with an objective of continuous monitoring and identification of significant rip channels along Visakhapatnam beaches from video imagery data by adopting and implementing an open-source, Quantitative Coastal Imaging Toolbox (QCIT). Ten minutes of video data were collected from temporarily installed camera for different months. Later, QCIT was used to pre-process the video data, camera calibration, domain definition followed by rectification products. Rectification products contain single image products and pixel instruments. Single-image products such as Timex, and bright and dark images are obtained by calculating the average, maximum, and minimum intensity on the rectified frames, respectively. The phenomenon of persistent gaps in wave-breaking events that appear as dark spots on bright background from Timex images shows quasi-permanent rip channels. The locations of the rip channels extracted from the Timex images were accurately well matched to the hotspot maps of the rip currents obtained from the high-resolution satellite images, drifter and die experiments at the study site. However, once the video camera is permanently set up, further statistical analysis with continuous data availability is also possible. Further implementation of this study would be helpful in the continuous monitoring of coastal rip currents, other coastal parameters (i.e., alongshore currents, shoreline mapping, wave run-up, and up-to-date nearshore estimated bathymetry), and implementation of numerical modeling of coastal processes by supplying better inputs. With these essential results, ESSO-INCOIS and SAC-ISRO have embarked on a project with the primary objective of continuous monitoring and issuing operational forecasting alerts of rip currents by developing a coastal video surveillance system that also provides information on complex coastal and nearshore processes.