Lotte Chemical Indonesia aims to develop a new naphtha cracker plant on reclaimed land in Cilegon, Banten province, Indonesia. The project site is however at risk from tsunamis generated by earthquakes as well as from tsunamis generated by major volcanic eruptions and associated landslides. Insight in the tsunami risk as well as in the effects of an occuring tsunami are vital for the design of the land reclamation.
Royal HaskoningDHV was asked to carry out a tsunami hazard assessment, derive design conditions for the marine structures, determine the required land elevation of the reclamation and assess possible protection measures against tsunami flooding.
A numerical modelling approach, using the MIKE software, was adopted to predict water levels and currents, caused by several tsunami events. Tsunamis generated in the Sunda Trench following earthquakes were analysed and a 1/100 year and 1/1000 year event was derived. Besides earthquake-generated tsunamis, tsunamis following volcanic eruptions and associated landslides were assessed, using historical information on the 1883 and 2018 volcanic events at Krakatau Island. Forcing the model with these events, water level and current design conditions were derived at the project site.
In order to protect the plant site from tsunami flooding a wave wall was proposed. Using a wave overtopping model, the height of the wall was optimized to reach the required level of protection.