Tourist development, morphology and tsunamy risk in Antofagasta (Chile): an uncertain equilibrium

The city of Antofagasta is located on a coastal terrace formed by marine abrasion, mainly in the Quaternary period. It is bordered by the sea on one side and by a steep mountain face rising to great heights on the other (Cordillera della Costa). Because the terrace is broader in the northern sector (more than 3 km wide), the expansion of the city – which has already taken place along the coast covering an area of around 30 km – is now mainly taking place in this direction. The rapid topographic development of the city at the end of the 1930s was linked to the building of a large port serving the whole of northern Chile for the loading of mineral resources from inland areas (mainly saltpetre, but also copper) and replacing the smaller port of Coloso situated to the south of Antofagasta. In the course of time this development continued to strengthen, adopting a settlement pattern that involved little planning and was often chaotic (not least because of the particular morphology of the land with its large quantity of aeolian deposits and alluvium). Only in its initial stages did urbanisation follow the grid pattern layout of traditional South American city planning. What has taken place, therefore, is an intense process of humanisation of the landscape of a coastal ecosystem whose equilibrium has never been more fragile: the immense force of the wave motion along the entire coastal belt demands continuous interventions to protect the ports and beaches. In fact, while still an important mineral centre and port (a new and nationally strategic port is currently being created to the north of the city), Antofagasta is also trying to develop its tourist potential, thanks to the expansion and redevelopment of existing facilities (the creation of housing blocks, road infrastructure, artificial beaches and green areas). A number of public works are also being carried out to improve the city’s general appearance, as laid down in the Bicentenary Project – Chile 2010. Policies regarding urban renewal and tourist development must, however, give due consideration to the fact that Antofagasta is subject to a high tsunami risk. Already in 1997 SHOA drew up a chart showing areas of flooding by tsunami in the city, based on two important events that took place in 1877 and 1995. An analysis of the most recent of these events showed how the gradient of the submerged beach can effect the rising of the water mass over the coast. In specific terms, the 1995 tsunami was recorded as being “non-destructive” because of the low levels it reached and the small extent of damage it caused (due in part to the day and time on which it occurred – a Sunday night at low tide). However, what would happen if the morphology of the sea floor in the Antofagasta area were modified in order to accommodate new economic structures and tourist facilities