Building Site Location Overview

Building structures located in the coastal areas of Indonesia, where tsunamis or earthquakes are expected to happen, have a high index of vulnerability. There are a number of known faults as can be seen in the black lines in the below diagram (click image for a larger version):

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Image source: https://commons.wikimedia.org/wiki/File:Geology_indonesia_map.jpg

Choosing a Location to Build

Most of the structures observed within the vulnerable areas in the coasts of Indonesia, are built with common materials such as brick, block, and reinforced concrete. Other materials observed in the areas are palm tree and bamboo, which are commonly used due to their low cost and availability in the region. Even though the construction practices and materials used are like those used in other countries, Indonesia has higher risks to structure damage by natural disasters due to the closeness to the Australian fault and for the typical terrain of the area, which is prone to heavy rains and subsequent land and mudslides.

This means that Indonesian's need to pay special attention to their building location choices to ensure safety in relation to natural hazards, including subsidence (caving in or sinking of an area) or liquifaction (strength or stiffness of the soil is reduce due to earthquake shaking).

Highly Populated Areas

Community housing in Indonesia has a combination of structures that have been built over flat or sloped areas, especially in areas such as Palau Lombok. In the case of more populated areas such as the island of Bali, from Denpasar to Kuta, housing is observed to be in flat areas mostly close or at sea level. The overpopulation in this area makes every meter of land very valuable and structures are very close to each other. This creates an array of alleyways that can rapidly channel water in the case of a tsunami. Additionally, this makes evacuation challenging as there are limited pathways within and between buildings. In some cases, viable pathways have been restricted or blocked for building security purposes. In considering the diagram with Hanif, for example, if all the residents of the local hotel and shops needed to evacuate from this alleyway there would be significant congestion. If an item were to fall and block or impede the path (such as debris in flowing water) the challenges of evacuation would only be magnified. While this alleway is only about six feet wide (1.8 meters), it is recommended that all alleyways be a minimum of 12 feet wide (3.6 meters) although preferably up to 20 feet wide (6 meters) so there is ample space in the case of a large evacuation.

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Hanif in hotel entry alley in Bali

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