Assessment of reliable wave climate at jetty on open coasts: role of 2D spatio-temporal spectrum

Abstract

The development of coastal roads and bridges is important to overcome traffic congestion in densely populated coastal cities like Mumbai. In the present study, the importance of assessment of wave conditions required for the extension of jetties to facilitate the transportation of bridge components to build the sea link bridge during non-monsoon season is envisaged so that zero downtime for operability at jetties is ascertained. Coupled hydrodynamic spectral wave model (Telemac-2D and TOMAWAC) used to hindcast waves reveals that the application of spatio-temporal varying 2D directional spectrum (from ERA-5) over the offshore boundary as a forcing function helps in propagation of realistic wave climate of Mahim Bay, Mumbai. Coupling of the TOMAWAC-ARTEMIS model is essential to obtain reliable wave conditions near the jetties (nearshore) for predominant directions. The study reveals that under existing conditions, downtime at proposed jetties will be for 30 days wherein Hs ≥ 0.3 m. As such to achieve zero downtime, the existing bund on the seaward side of jetties was extended optimally (70 m) so that smooth operability for the entire non-monsoon is achieved. Thus, application of spatio-temporal varying 2D spectrum in optimising the length of the guide bund has been found promising for speedy transportation of proposed bridge components. The study also reveals that there is an insignificant climatological impact on wave conditions.