Author(s)

O. Hanada, Y. Yamada, M. Takezawa & S. Tamai

Abstract

The height and distance of splashing generated by sea waves were simulated in a wave tank with a wind tunnel, and the prevention of salty wind damage is considered in the present study. The model test was carried out using a two-dimensional wave tank (length: 30 m, width: 0.7 m, and depth: 1.2 m) with a wind tunnel. A 1/20 model of the seawall was set up on a fixed bed with a 1/15 slope at the end of the wave tank. Models of the concrete armor units were placed in front of the seawall in four rows and two steps. The windbreak net models were made of a 2 mm x 2 mm mesh. The heights of the windbreak nets were 15 cm and 20 cm. The windbreak net was set up at positions of 10 cm, 20 cm, 30 cm, 40 cm, and 50 cm behind the seawall. The main conclusions of the present study are that the splashing behind the seawall is prevented by the windbreak net, and the splash height is affected by concrete armor units placed in front of the seawall. Keywords: salty wind, seawall, concrete armor unit, windbreak net. 1 Introduction Salty wind blowing over seawalls due to retreating shorelines increases damage to coastal vegetation and buildings. Seawater corrodes metals and rots vegetation. Salty wind damage is particularly severe in rough weather. For example, black pines along the Futtsu coast in Chiba prefecture died due to salty wind during the spring shoot season. In addition, all of the trees in the forest reserve at Nagaishi coast in Niigata prefecture died due to splashing salty wind, and vegetables were extensively damaged by salty wind at Mitsutoyo, an area of reclaimed land in Kagawa prefecture [1, 2]. In this study, windbreak nets behind the seawall and structures in front of the seawall to prevent salty wind are investigated by hydraulic model testing using a two-dimension wave tank with a wind tunnel.

Keywords

salty wind, seawall, concrete armor unit, windbreak net.