Nearshore wave analysis from coastal video monitoring techniques at high energy micro tidal beach under sunlight dominance conditions: A case study from Valiathura beach in southwest coast of India

• Published in: Regional studies in marine science 2022-03, Vol.51, p.102205, Article 102205
• Main Authors: Ramesh, Madipally, Nair, Leela Sheela, Anoop, Thondithala Ramachandran, Prakash, Thirumali Nageshrao
• Format: Article
• Language: English
• Subjects: Modulated transfer function; Multi-tapered spectral estimates and wave analysis; Video monitoring
• ISSN: 2352-4855; 2352-4855
• DOI: 10.1016/j.rsma.2022.102205

Continuous collection of hydrodynamic data from the nearshore region by deploying marine instruments is challenging, mainly because of the huge cost and risk involved in keeping these sophisticated instruments in the highly dynamic nearshore region, since the area is often subjected to harsh environmental conditions. In such situations, adoption of remote sensing methods like use of land-based camera stations for continuous monitoring is advantageous due to its low risk and cost-effective features and ability to provide data during extreme events. In this connection, National Centre for Earth Science Studies (NCESS) has initiated a pilot project for continuous coastal monitoring, adopting the video-based monitoring method in India through an indigenous Video Beach Monitoring System (VBMS). The first VBMS station, comprising of four cameras have been installed at Valiathura, a typical high energy beach in SW coast of India and the software tools for deriving coastal morpho-hydro dynamic characteristics from video imagery are being developed. For estimation of wave characteristics, the use of linear transfer function methods has limitations in highly dynamic nearshore environments and the varying sunlight conditions during AN sessions along west coasts will also have serious impacts on the analysis. These difficulties can be addressed by adopting a modulated transfer function (MTF) approach. In this paper, an improved nearshore wave analysis from video timestacks, using MTF approach is discussed. The developed MTF uses multi-tapered spectral methods wherein the periodograms are averaged to reduce the effect of non-linearities as well as the variations due to sunlight in the spectral density. The computed significant wave height, mean wave period and peak period adopting this function corroborate well with the measured in-situ wave data. •A new video beach monitoring system (VBMS) has been introduced in southwest coast of India.•An improved site-specific modulated transfer function is designed for nearshore wave analysis using video imagery, for a high energy coast.•Issues from the impacts of sunlight on video imagery are significantly addressed during the pre-monsoon period.