AN EXPERIMENTAL STUDY OF SOLITARY WAVE PROPAGATION THROUGH EMERGENT RIGID VEGETATION ZONE Xiaochun Tang, Pengzhi Lin * State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, China *Email:cvelinpz@126.com Abstract A lot of aquatic plants in coastal area are observed to have significant effects on wave transformation and wave energy dissipation when wave propagation through vegetation zone. In this study, the experiments were conducted to investigate the wave transformation and wave velocities by wave gauges and PIV measurements. The vegetation zone was modeled by PMMA (polymethylmethacrylate) cylinders, which are rigid and emergent. The PIV measurements were firstly validated with the theoretical formulations under pure solitary wave conditions. The PIV measurements were then employed to study the interaction of solitary wave with vegetation stems. Based on the results, the characteristics of velocity profiles front and behind the vegetation stems are discussed. Other tests were also conducted to investigate the influence of vegetation on different vertical plane. Key Words: solitary wave, rigid vegetation, PIV, velocity profiles 1. INTRODUCTION Aquatic plants in coastal area can significantly influence the hydrodynamic characteristics of flows, such as the velocity distribution and turbulence. Aquatic vegetation increases the flow resistance and decreases the flow speed [1, 2], thus promoting sediment deposition [3, 4] and protection of shoreline. Vegetation can also attenuation wave height and dissipate wave energy [5-12]. Furthermore, vegetation is responsible for water quality and species diversity [13]. Many researchers have studied this topic in recent years theoretically [5, 12, 14], experimentally [6, 7, 10, 11, 15, 16], or numerically [8, 9, 17, 18]. Field measurements have also been collected [19, 20]. A lot of the studies have been conducted as well, focusing on water surface variation and drag force generated from the interface of flow and vegetation. There isn’t so much information about flow velocities of interaction of solitary wave with vegetation in the literature due to the unsteady and non-uniform characteristics of waves. Fortunately, many researchers have studied the velocity distributions and turbulence structures of flows under steady and uniform conditions. Raupach et al.[21] have conducted a series of experiments in a wind tunnel to investigate the turbulence structures within and above vegetation canopies by using hot-wire anemometers. Nepf[1] have studied the drag force performance, diffusion characteristics, velocities distributions and turbulence in emergent vegetation zone by Acoustic Doppler Velocimetry (ADV) and Laser Doppler Anemometer (LDA). Furthermore, Nepf and Vivoni[22] have used the same facilities to investigate the influence of submergence on flow velocity and turbulence structures, they found there were some difference between vegetated open-channel flows and terrestrial canopy flows,