圖書典藏及影音數位平台

本署已執行一系列有系統的研究評估氣候變遷對全臺灣海堤設施的衝擊，並且分析全臺灣沿海地區暴潮溢淹的風險。而自然海岸侵蝕與近岸沙洲變遷問題則因為觀測資料較少，且模擬技術也尚未發展成熟，所以尚未評估。未來在全球氣候變遷現象的影響下，臺灣的自然海岸侵蝕與近岸沙洲變遷問題可能更為嚴重。因此，有必要在既有資料的基礎上，探討可能的衝擊與因應對策。為評估氣候變遷下臺灣自然海岸侵蝕與近岸沙洲變遷對沿海地區的衝擊，以預先規劃因應策略，爰辦理本計畫。

The Water Resources Agency, MOEA, has been systematically implemented a series of studies to assess the impact of climate change on the regions with seawalls and to analyze the risk of overtopping around coastal areas in Taiwan. However, the impact of climate change on the natural coasts and the sand barrier has not yet been assessed. Many of the impacts of global warming become worse and have been widely recognized. Therefore, there is a need to figure out the impacts and the countermeasures due to climate change based on the existing measured data and previous study. For this purpose, the program is conducted for two years (2017 and 2018). The first year, the main works are to figure out the impacts on the natural coasts in Taiwan with considering several conditions due to climate change. The second year, the study focuses on the impact of climate change on the offshore sandbar around Taiwan. Collecting and analyzing the information about the impact on the natural coastal erosion due to climate change in abroad, the analysis of natural coastal erosion in Taiwan, and the case studies in Taiwan are the major works. By doing so, the method of assessment for climate change to coastal hazards, the simulation of the impact on the coastal hazard, the analysis of the vulnerability and risk are constructed. These results provide useful information to set up the adaptation strategy and to implement the benefits analysis of the operation program. Two periods (1980-1999 and 2020-2039) are used to be the condition of climate change to investigate the influence of the natural coasts and the sand barrier due to climate change. The sea sates in these periods (1980-1999 and 2020-2039) are derived from the pressure and the wind fields using General Circulation Model (GCM). Combination of the ECMWF re?analysis project data and the changes of the sea states from the climate model, the variation of the natural coasts and the sand barrier from 2020 to 2039 is simulated. The influence of the presented coastal protection due to climate change and the change of the natural coasts and the sand barrier is analyzed. The work in the first year is to analyze the impact of climate change on natural coasts. The study area is at Shuang-Chun coast in Tainan. The results show the change in the erosion disaster is more significant than the inundation disaster, and the global sea level rise is the critical factor. The variation due to climate change is based on the MRI-GCM3. The computed wind and pressure fields show the increase in water waves in the summer (winter) between 1980-1999 and 2020-2039 is 1.02 (1.03). Besides, the increase in design wave condition and storm surge are 1.12 and 1.23 respectively. These results show the strength of the monsoon waves has a little increase, yet a significant increase in the extreme condition. The work in the second year is focused on the impact of climate change on the sand barrier. The study area is at the coast from Yunlin to Chiayi. The results show the evolution of the sand barrier is also a factor to influence the natural coasts. Besides, the climate change in the future is discussed by a series of climate models using ensemble averaging method. In the period from 2020 to 2039, the results show the design wave height with the return period of 50 years increments of 1.025 times. Also, the average increments of the storm surge, the significant wave height in summer and the significant wave height in winter are 1.084, 1.020 and 0.981 times, respectively. Furthermore, the area of the sand barrier in the period from 2020 to 2039 is half of the current state. This phenomenon would lead to a change of the flow field in the coastal region of Shuang-Chun district, and make the sand barrier in the region from Yunlin to Chiayi have the possibility of a sustained retreat. The government should have to pay more attention to the area around the Beimen seawall in Tainan because the impact of climate change on this area is significant.