Wave elimination mechanism of wavebreak forest by physical experiments in Baidajie Dike, Nenjiang River of northeastern China

ObjectiveTaking the Baidaijie Dike in Nenjiang of northeastern China as the research object, this paper aims to study the influence of each factor on wave-elimination effect of Nenjiang Mainstream wavebreak forest, and to optimize the layout of the forest.

MethodAccording to the gravity similarity criterion, the forest in the study area is reduced to a laboratory sink by reasonable scale scaling to simulate the process of the effect of the vegetation on the wave. In the experiments, waves are generated by the wave generator, the wavebreak forest is simulated by the model tree and thus a suitable physical model of the wavebreak forest is constructed. The main control variable method is adopted, and the width, density, arrangement mode of wavebreak forest, tree shape and wave height on the beach were taken as the influential factors. Grouping experiments were conducted. And in each group, the changes of wave-eliminating effect of wavebreak forest under the change of a certain factor were simulated to determine the influence of each influencing factor on the wave-eliminating effect. And based on the experimental results of the optimization scheme, some complicated factors are combined and the optimal design scheme is proposed.

ResultThe results showed that under reasonable conditions of tree shape, the wave-elimination coefficient of 30−40 m of the width of the forest was above 30%, and the increase of the wave-elimination coefficient of the larger forest width was not significant. Taking into account the economic and rational factors, 40 m of the width of the forest was more reasonable. Forests with equidistant triangles arranged mode were relatively superior, and can meet the needs of greater row spacing and more suitable for the conditions of light, growth and health of the wavebreak forest. The increase of vegetation density can improve the wave elimination coefficient, but when the vegetation density was more than 0.17 plant/m², the wave elimination coefficient cannot be increased significantly. And it is suggested that the vegetation density should be about 0.17 plant/m², which can fully guarantee the plant spacing, more conducive to the growth of forest belt. Meanwhile, when the wave height is in the crown position, the wave-eliminating effect is good; and the higher the wave height was, the better the wave-elimination effect was.

ConclusionThe optimal design scheme in research area is under the reasonable tree type condition, the width of the shelterbelt is 40 m, the arrangement is equilateral triangle, and the density is about 0.17 plant/m².