NEW TSUNAMI HAZARD ASSESSMENT OF CHAÑARAL, CHILE, AFTER THE COASTAL MORPHOLOGY CHANGES DUE TO THE 2015 RIVER FLOOD

Abstract

Chañaral is a town located at the mouth of the Salado River in northern Chile (Lat 26.3 °S). The main economic activity in its vicinity is copper mining, such as at Potrerillos and El Salvador. The river mouth is typically closed due to the coastal sediment transport. In addition, a large reclamation area was built from mine tailings and a highway was constructed on an elevated levee in the reclamation area. Furthermore, Chañaral is under tsunami hazard, with the last tsunami event taking place in 1922. According to historical records, the tsunami reached 10 m (Soloviev & Go, 1975). This event occurred prior to the deposition of mine tailings, which started in 1930. The official tsunami inundation map was made in 2014, and the tsunami scenario considered an extreme event based on the 1922 tsunami plus a high tide (SHOA, 2014). The maximum tsunami runup was estimated to be 17 m. In March 2015, a heavy rain event took place over the Atacama Desert and a catastrophic flood affected Chañaral, with a maximum water depth of 4.5 m (Wilcox et al., 2016), significantly changing the coast. In fact, the elevated highway was destroyed and there was substantial coastal erosion. The present work assesses the tsunami hazard considering the new coastal morphology, given that coastal erosion would allow a tsunami to easily surge into the river and subsequently the town.