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Abstract. On 22 December 2018, a tsunami was generated from the Mount Anak Krakatau
area that was caused by volcanic flank failures. The tsunami had severe
impacts on the western coast of Banten and the southern coasts of Lampung in
Indonesia. A series of surveys to measure the impacts of the tsunami was
started 3 d after the tsunami and lasted for 10 d. Immediate
investigations allowed the collection of relatively authentic images of the
tsunami impacts before the clearing process started. This article
investigates the impacts of the 2018 Sunda Strait tsunami on the affected
areas and presents an analysis of the impacts of pure hydrodynamic tsunami
forces on buildings. Impacts of the tsunami were expected to exhibit
different characteristics than those found following the 2004 Indian Ocean
tsunami in Aceh. Data were collected from 117 flow depths along the Banten
and Lampung coasts. Furthermore, 98 buildings or houses were assessed for
damage. Results of this study revealed that the flow depths were higher in
Banten than in Lampung. Directions of the tsunami arrays created by the
complex bathymetry around the strait caused these differences.
Tsunami-induced damage to buildings was mostly the result of impact forces
and drag forces. Damping forces could not be associated with the damage.
The tsunami warning system in Indonesia should be extended to anticipate
non-seismic tsunamis, such as landslides and volcanic processes driven by
tsunamis. The lack of a tsunami warning during the first few minutes after the
generation of the first wave led to a significant number of human casualties
in both of the affected areas.

Abstract. This research aimed to assess the tsunami flow velocity and height reduction produced by a planned elevated road parallel to the coast of Banda Aceh, called the Banda Aceh Outer Ring Road (BORR). The road will transect several lagoons, settlements, and bare land around the coast of Banda Aceh. Beside its main function to reduce traffic congestion in the city, the BORR is also proposed to reduce the impacts of future tsunamis. The Cornell Multi-grid Coupled Tsunami Model (COMCOT) was used to simulate eight scenarios of the tsunami. One of them was based on the 2004 Indian Ocean tsunami. Two magnitudes of earthquake were used, that is, 8.5 and 9.15 Mw. Both the earthquakes were generated from the same source location as in the 2004 case, around the Andaman Sea. Land use data of the innermost layer of the simulation area were adopted based on the 2004 condition and the land use planning of the city for 2029. The results of this study reveal that the tsunami inundation area can be reduced by about 9 % by using the elevated road for the earthquake of magnitude 9.15 Mw and about 22 % for the earthquake of magnitude 8.5 Mw. Combined with the land use planning 2029, the elevated road could reduce the maximum flow velocities behind the road by about 72 %. Notably, the proposed land use for 2029 will not be sufficient to deliver any effects on the tsunami mitigation without the elevated road structures. We recommend the city to construct the elevated road as this could be part of the co-benefit structures for tsunami mitigation. The proposed BORR appears to deliver a significant reduction of impacts of the smaller intensity tsunamis compared to the 2004 Indian Ocean tsunami.