This paper presents post-tsunami survey results describing the impacts of the 2011 East Japan tsunami in Yos Sudarso Bay, Papua, Indonesia. Although the far-field tsunami had a height of 0.8 m measured at a tide gauge inside the small U-shaped bay, it severely damaged four villages scattered along the bay. Detailed numerical analysis was carried out to explain the damages. We used a well-verified source model in the near- and far-field cases to model the propagation of the tsunami southward in the Pacific until reaching Papua Island, Indonesia. The numerical analyses demonstrate two causes of damage in the bay: the maximum tsunami velocity (3.5 m s(-1)) floated the houses in the villages of Tobati and Enggros and caused them to collapse, and water trapped by the hook-shaped peninsula amplified the tsunami height at the Holtekamp and Hanurata.

We report here on the observation and offline detection of the weak tsunamis generated by earthquakes near Indonesia on 11 April 2012 using radar systems and tide gauges on the coasts of Sumatra and the Andaman Islands. This work extends the previous observations of the much stronger 2011 Japan tsunami. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends primarily on the bathymetry: the wider the shallow continental shelf, the greater this time. The weak Indonesia tsunamis were detected successfully in spite of the narrow shallow-water shelf offshore from the radar systems. Larger tsunamis could obviously be detected further from the coast. This paper provides further confirmation that radar is an important tool to aid in tsunami observation and warning.

This paper describes tsunami disaster mitigation in the West Sumatra region with participatory technology assessment (pTA), which promotes direct interaction among member and experts to discuss issues and reach consensus for mitigation through provision of information and knowledge of science and technology. Two areas were examined: Padang, the capital city; and Painan city, a town in southern West Sumatra Province, Indonesia. Tsunami have damaged these areas at least three times: in 1797, a 5–10-m-high tsunami wave height hit the area; in 1833, a 3–4-m-high tsunami came; and in 2007, an 8.4 Mw earthquake generated a local tsunami with maximum wave height of 1.5 m, as observed near Painan. Because of the high level of tsunami risk resulting from its flat topographic conditions, their respective populations of 820,000 people and 15,000 people are developing tsunami mitigation efforts with support of national institutions and international experts. These cities had different starting points and approaches. Efforts were introduced to produce official tsunami hazards maps. Insights from these lessons and ideas arising from the ongoing process after the 2007 South Sumatra and 2009 Padang earthquakes are discussed herein.

Padang, West Sumatra, Indonesia is considered to have one of the highest tsunami risks in the world. Currently, the strategy to prepare for a tsunami in Padang is focused on developing early warning systems, planning evacuation routes, conducting evacuation drills, and educating the public about its tsunami risk. Although these are all necessary efforts, they are not sufficient. Padang is located so close to the Sunda Trench and has such flat terrain that a large portion of its populace will not be able to reach safe ground in the interval—less than 30 minutes—between the time the earthquake shaking stops and the tsunami arrives at the shore. It is estimated that over 100,000 inhabitants of Padang will be unable to evacuate in that time, even if they head for safe ground immediately following the earthquake. Given these circumstances, other means to prepare for the expected tsunami must be developed. With this motivation, GeoHazards International and Stanford University partnered with Indonesian organizations— Andalas University in Padang, the Laboratory for Earth Hazards (LIPI), and the Ministry of Marine Affairs and Fisheries (KKP)—in an effort to evaluate the need for and feasibility of developing Padang’s tsunami evacuation infrastructure. This project team designed and conducted a course at Stanford University, undertook several field investigations in Padang, and participated in a reconnaissance trip following the September 30, 2009 earthquake. The team concluded that: 1) the tsunami-generating earthquake is still a threat, despite the recent M7.6 earthquake; 2) Padang’s tsunami evacuation capacity is currently inadequate, and evacuation structures need to be implemented as part of an effective evacuation plan; 3) it is likely that previous estimates of the number of people unable to evacuate in time are grossly low; and 4) a more engineering-based approach is Project Manager, GeoHazards International, Palo Alto, CA 94301 2 Graduate Student, Dept. of Civil Engineering, Stanford University, Stanford, CA 94305 3 Professor, Dept. of Civil Engineering, Stanford University, Stanford, CA 94305 4 Project Engineer, Tipping Mar, Berkeley, CA 94704 5 Professor, Dept. of Civil Engineering, Andalas University, Padang, Indonesia 6 Graduate Student, Dept. of Civil Engineering, Andalas University, Padang, Indonesia needed to evaluate the appropriateness of existing buildings to serve as evacuation sites.

In the last two years, the tsunami phenomenon has become a very serious issue in Indonesia. The 2004 Sumatra tsunami caused 130,000 casualties with another 37,000 missing, presumed dead, and financial loss suffered reached $ 4.3 billion. A tsunami struck the Pangandaran area again, West Java Province, on July 17, 2006, which caused 668 casualties with another 45 missing and financial loss reaching $ 44.7 million. The damage to these infrastructures and lives clearly shows that disaster mitigation and disaster countermeasure efforts are still not running well. This is becoming the background to the urgent need for integrated tsunami disaster mitigation to build a well-prepared coastal disaster community in the near future.

In spite of the importance of knowing sediment transport near a river mouth, it has not been well studied because of the complexity of exerting forces and topography. This study has developed an analytical model to reproduce large cuspate topography which has been often observed at the Abukuma River mouth.The velocity field of river flow is evaluated by the two dimensional jet model and the longshore current field by Longuet-Higgins's model. Along stream lines for the superimposed field of the two flows, the continuity equation of sediment is solved. Computational results for several river and wave conditions show that high river discharge is especially effective to form large cuspate topography. Keywords: sediment transport, river flow, longshore current, computation

The construction of the floodway of Krueng Aceh river mouth in Indonesia decreases the discharge of the river leading to develop a sand spit at the mouth. The sand spit in turn causes river mouth clogging and troubles in navigation. Nears hore current field near the mouth has complex distribution due to complexity of the topography near the mouth. In this paper, the wave deformation and near-shore current to evaluate sedimentation near the mouth was analyzed by means of datacollection, interview and field reconnaissance.