ABSTRACT

Buffer blocks, inspired by stilling basin blocks in dam construction, present a novel method for mitigating tsunami energy and protecting coastal areas. These structures generate vortices that reduce flow, enhancing energy dissipation while also serving as the seating avenue for beachgoers. Positioned a few hundred meters from the shoreline, the buffer blocks delay disaster impact and facilitate evacuation. This study examines different block shapes, viz., H-type, I-type, Plus-type, and Cross-type to optimize the energy dissipation. Numerical simulations using the IITM RANS 3D code reveal that these blocks enhance diffraction and reflection, promoting vortex formation and reducing momentum flux. The research aims to enhance the understanding of buffer block efficiency and its impact on flow behavior, thus, contributing to future coastal protection strategies.

INTRODUCTION

Extreme events, including tsunamis and storm surges, present severe risks to coastal populations, frequently leading to catastrophic conditions marked by significant loss of life and property (NOAA, 2013). Although warning systems have improved, their reliability is still not fully assured, highlighting the essential need for strong coastal defence mechanisms. The catastrophic 2004 Boxing Day tsunami spurred the creation of various mitigation strategies in India and worldwide (Sundar et al, 2020), focusing on energy dissipation as a crucial method to reduce damage.

Inspired by the design principles of stilling basin blocks used in dam construction (Peterka, 1984), buffer blocks have emerged as a possible promising solution for enhancing coastal resilience. These structural elements create partial obstructions to the flow, thereby improving energy dissipation. Unlike traditional defensive structures such as seawalls, buffer blocks offer advantages, including cost-effectiveness and minimal spatial requirements, making them particularly suitable for densely populated coastal areas.

Certain studies have emphasized the effectiveness of these blocks in minimizing overtopping and run-up, which subsequently led to investigations into their role in energy dissipation. Studies indicate that staggered buffer blocks dissipate tsunami energy more effectively than tandem arrangements (Goseberg,2013a and 2013b), highlighting the importance of block size and spacing. Giridhar and Muni Reddy (2015) conducted experimental research on energy dissipation blocks of various shapes (rectangular, semi-circular, and trapezoidal) placed on inclined structures, examining their effects on wave run-up and wave reflection. It was reported that the wave reflection for non-porous trapezoidal sections, square blocks and semi-circular shapes are 0.44, 0.37 and 0.23 respectively. Additionally, the wave run-up for the above three shapes are 3.27, 0.74 and 0.74 respectively.

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