Experimental investigation on tsunami impact reduction on a building by a Mangrove forest

Mangroves have a remarkable wave dissipating effect. An experimental study on the tsunami impact building model and mangrove protection effect was carried out. The dam breaking wave was used to simulate the tsunami wave, and the mangrove and building models were installed in the flume. The protective effect of mangroves was studied by measuring the bore height before and after the tsunami wave passed through the mangroves and pressure during tsunami bores impacting buildings and pressure around the building during tsunami bores. The results show that, in all cases, bore heights reduced by mangrove are increased by building obstruction. On the premise that the mangroves are not destroyed, the disaster mitigating effect will not be affected by the wave intensity, but will increase with the mangrove density. Among the three arrangements, the annular arrangement has the best mitigating effect. The process of the tsunami bore impacting the building is divided into four stages: front-hitting, run-up, quasi-steady and recession. Under the protection of mangroves, the pressure at each stage is significantly reduced. For front-hitting pressure, the maximum pressure no longer appears here but in the run-up stage. For quasi-steady pressure, the time history of pressure will oscillate due to bubbles generated when the tsunami passes mangroves. According to Bernoulli principle, mangroves are determined to play a major role in reducing tsunami energy. Finally, based on the experimental data, equations for estimating the quasi-steady pressure in the center of the lower part of the building, and the distribution of pressure on the building are presented.