氣候變遷下海岸防禦的非工程治理: 海岸後退帶的試驗規劃與社會回應研究

The direct effects of global climate change include rising sea levels and a higher frequency of extreme meteorological events, such as typhoons or storms. In response to coastal erosion, engineered structures, such as seawalls, groins, and detached breakwaters, are frequently used in Taiwan to protect the shoreline and to prevent the loss of life and property in hazardous typhoon events. However, these protective measures are clearly lacking in their adequacy to combat strong waves and storm surges. Moreover, the damage repairs needed are too costly for the government to afford. Even worse, the presence of such concrete structures also result in negative effects on beach preservation in adjacent areas. Now it is the time to transform traditional techniques of protection and embrace approaches that involve "soft engineering" or other environmental governance approaches that involve no engineering at all. This study draws upon foreign experiences in setback zones and investigates long-term shoreline changes and shoreline retreat rates. Using such findings, we aimed to propose an estimation of the expected shoreline position in the future 30 or 60 years. However, the findings showed that the shoreline did not change much in the first half of the last century. Most of the shoreline retreats were found within the most recent 30 or even 20 years and were the combined result of heavy human activities on the coast and the global rise of sea levels. Directly using the 100-year long-term shoreline retreat rate to estimate the future trend would have been inappropriate. Instead, we surveyed current land use and economic development in the coastal zones and suggested that future setback zoning should be based on the local development in individual coastal reaches. For less developed shorelines, Miao-Li coast as an example, the setback zoning approach should be applied immediately. On the other hand, coastal communities in the more developed areas, for example the Tainan coasts, should be educated about the causes and results of future coastal changes. Once armed with the awareness of potential impacts on nearby shorelines and the need to minimize such impacts, local residents should be given the chance to vote for their future. In this year’s societal response survey, we found that, as people’s awareness of coastal sciences and the consequences of climate changes have risen, setting up traditional hard structures is no longer the only recognizable option. More people are willing to adopt the setback zone approach based on appropriate setback planning by the government. The adaptive soft engineering works are also welcomed, with landscape and ecology conservation being taken into consideration. Seventy-five percent of the surveyed group of people suggests that setback zone planning, combined with soft adaptive engineering work such as the rebuilding of coastal dunes, will allow preservation of the natural landscape and ecological system while reducing life and property losses in coastal hazardous areas.