Mon, Jan 15, 2024 page8

• Earthen walls and disaster prevention

  • By Johnson Kung 拱祥生
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  On New Year’s Day, Japan’s Noto Peninsula was hit by a magnitude 7.5 earthquake, resulting in heavy casualties. I am a civil engineer and a member of the Tainan Fire Bureau Search and Rescue Team, but I was unable to help with rescue efforts in the disaster zone, as Japan politely declined offers of international rescue assistance.

  However, I took a few days off from work to travel to the area and conduct a preliminary survey.

  The main disaster causes were soil liquefaction and the collapse of old houses built with woven bamboo and mud walls. This raises the question of whether Taiwan could handle such a seismic disaster.

  The areas hit hardest by the earthquake include Wajima, Shushu and Anamizu in the north of the peninsula. My survey focused on Nanao, which lies in the peninsula’s center.

  As soon as I arrived, I saw signs of small-scale soil liquefaction along the road, causing protrusions, subsidence and cracks in the road surface. Houses in the disaster area are all three stories or lower in height. Soil liquefaction is affected by a high water table and the distribution of soil composed of different particles. Soil liquefaction only damaged homes in parts of Nanao, mostly in the form of toppled and collapsed old houses with woven bamboo and mud walls — the main cause of casualties.

  During Qing Dynasty rule and the Japanese colonial era, many houses in Taiwan were built with woven bamboo and mud walls. The main materials in these homes, some of which still exist, were makino bamboo, mud and rice husks. When the 921 Earthquake hit, many earthen-walled houses collapsed, and although they were not as heavy as brick walls, the weight of fully collapsed roofs and entire houses was still enough to cause death and injury.

  How many people in Taiwan still live in such weak and aging homes? This question should be a focal point for the Ministry of the Interior. Furthermore, one key point of the ministry’s earthquake-proofing reinforcement measures should be how to reduce casualties when earthen-walled houses are struck by earthquakes.

  In the Noto Peninsula earthquake, heavy snowfall and inconvenient transportation exacerbated secondary disasters. Water stoppages and power outages worsened the situation. The main reason for water supply interruptions is water pipeline ruptures. If a disaster hits an area with emergency backup wells for war preparedness or drought relief, these wells might be an emergency solution, and should be another disaster prevention measure for Taiwan to consider. This would be critical if a disaster zone becomes isolated from outside supplies. As for power outages, they are caused by power line damage. If disaster strikes an area where solar panels have been installed on low-rise building roofs, they could provide some much-needed power.

  Search-and-rescue teams should consider more lightweight rescue and relief equipment for deployment to hard-to-reach disaster zones. Any medium-sized search-and-rescue team in Taiwan consists of about 70 people with rescue equipment weighing several tonnes. How could such a team have reached the Noto Peninsula to help with disaster relief? In a scenario where all the collapsed houses are built with woven bamboo and mud walls, a team using lightweight equipment would have a good chance of rescuing many people and reducing casualties.

  Let us pray for the Noto Peninsula disaster victims and hope that their lives could soon return to normal.

  Johnson Kung is a board member of the Taiwan Professional Civil Engineers’ Association and a member of the Tainan Fire Bureau Search and Rescue Team.

  Translated by Julian Clegg
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