Tsunamis are disasters that cause so much damage. In the history of the tsunami, Indonesia has been hit by tsunami several times, based on data from the National Disaster Management Agency (BNBP), as of 1629 - 2007, Indonesia was recorded 184 times affected by large and small tsunami disasters. Based on these data, it is very important for Indonesia to increase security against the tsunami disaster. Also, the tsunami in Indonesia occurred due to earthquakes, volcanic eruptions, and landslides in the sea. This study discussed about to the tsunami with a location located in the southern of Java, precisely in the area of Central Java, considering that in 2017 there was friction between the Indies and Eurasian plates which caused an earthquake measuring 6.9 magnitude, but did not cause a tsunami. In this study, a tsunami wave propagation simulation was carried out with the aim of knowing how long it would take the waves to the shoreline and how high the waves would be when they were on the shoreline. The model used is a tsunami model created by Imamura by solving differential equations using finite difference and Runge-Kutta 4th order. Based on the simulation results with the initial determination of a 5 m tsunami wave centered at a distance of 25 km from the shoreline, Tsunami waves with a height of 8.7 m will arrive at the shoreline at 140 seconds. With wave height is 8.7 m at the shoreline, the water will enter the land or can also be called the tsunami disaster. At that time, residents are expected to have been evacuated from the coastal area. In addition, based on numerical simulations that have been carried out, information is obtained that the computation time of the method is faster than the computation time of the Runge-Kutta method with differences in altitude results that are quite small and can be tolerated. This shows that the Finite Difference method can be applied to tsunami disaster mitigation software because it has a fairly fast computing time compared to the Runge-Kutta 4th order method.

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Indonesia is a country flanked by 3 active plates and has many active volcanoes. This condition makes Indonesia susceptible to tsunami disaster. In 2018 Indonesia was hit by two tsunamis. The cause is plate friction and volcanic activity. Tsunami waves have a unique characteristic, the height of a tsunami wave in the middle of the sea is the same as ordinary waves, but when it reaches the shoreline the height gets higher. The reason is the increasingly sloping coastal contours. Coastal contours in Indonesia generally changes, either naturally due to abrasion and erosion, or artificially like reclamation. Reclamation clearly impacts the slope of the coast, causing different tsunami heights. This study discusses the impact of Reclamation on tsunami heights. Using the TUNAMI Mathematical Model, the results obtained are the height of the tsunami at the shoreline before Reclamation of 0.80 and the speed of 63.4 km / h, while the height of the tsunami after Reclamation is 0.87 and the speed is 70.5 km / h, so that the impact of Reclamation on the height and speed of the tsunami increases 8% and it can be concluded that the effect of Reclamation on tsunamis is to increase the risk of damage.

In this study, a high wave propagation simulation is conducted with several scenarios that include water's depth or seafloor topography's scenario and mangrove forest. The seafloor topography scenario is included because Indonesia has a quite different seafloor topography. The mangrove scenarios are included in this study because it will be seen how the effects of mangrove forests influence to reduce the height and velocity of waves. After the results of numerical simulations that have been carried out, it is obtained some information that the depth of waters and mangrove forests can contribute to the propagation of waves. Both can play a role to reduce the wave height to arrive at the mainland about 0,02 meters. It also can reduce the speed of the wave. With some results of the analysis obtained, how we provide obstacles can be done to reduce the impact of the risk of high waves, one of which is by planting mangrove forests. Further research is needed to learn the cause of the difference between negative velocity and time to wave that is fast enough even if given obstacles.