Author(s): Novi Andhi Setyo Purwono; Nizam; Radianta Triatmadja
Linked Author(s): Radianta Triatmadja
Keywords: Coastal protection; Tsunami; Greenbelt
Abstract: A Tsunami wave carries an enormous amount of energy that make the wave has a destructive power and causing devastating properties damages and a loss life when it reached the coastal area. The velocity of tsunami could reach 150-500 km/h. Research about vegetation uses as the energy of tsunami wave reducer were still considered as a rare topic. One of the research about such cases were done by Tetsuya Hiraishi (2003). Pacitan beach is one of coastal area that is used to simulate the use of vegetation in reducing tsunami wave as a grindbelt system. The aims of this study is to analyze the influence of canopy density and layout of the greenbelt in reducing the force of tsunami waves. A physical modeling is carried out in the Laboratory of Hydrology-Hydraulics Engineering Science Study Center Gadjah Mada University using a wave channel of 16.80 m length, 1.0 m width and 0.8 m height. The channel was equipped with a dam break system as tsunami wave generator. The datas were collected on the condition of 1m length of the greenbelt with two variation of layout models, which are the pentagonal (GP5) and the rectangular (GP4) layout. The water depth in upstream area also varied, from 20 cm to 60 cm with 20 cm of differences. The measurement of wave force was done by using a series of instruments such as strain gage and data logger, meanwhile for data record, Adlink series in 1902 are used. The position of sensors for force measurement is defined based on the function of greenbelt length. Sensor 1 was located right in front of the greenbelt model, sensor 2 was located at 1/3L, sensor 3 is located at 2/3L, and sensor 4 is located behind the greenbelt model. Where L is the length of greenbelt model. The results of this study showed that the coastal forest with a canopy density of 55%can reduce the wave forces that are propagated to the shore around 230%, while canopy with density of 40%can reduce the force around 190%. The density factor and layout of vegetation are the important variables of the coastal forests in reducing the tsunami force.