The east coast of Taiwan (TWEC) includes Yilan, Hualien and Taitung countries and has a length of 420km. More than one million citizens live along TWEC. More than five million tourists visit to TWEC every year. TWEC has more rocky beaches than sandy beaches. TWEC faces directly to Pacific Ocean and has water depth more than 5000m in a short distance away from the coast. The max. sea-floor slope at TWEC is 1/10. TWEC locates at the main track of Western Pacific Ocean produced typhoons. Extreme large waves, storm surges, strong wind and heavy rains are the main phenomena brought by a typhoon. TWEC faces severe impacts from natural hazards.
More than 20 typhoons (tropic cyclones) generated in Western Pacific Ocean in a year. Some of them attack the east coast of Taiwan. Due to steep sea-floor slope and unsheltered at TWEC; the typhoon-generated waves are always extreme large and often cause serious damages on sea dykes, coastal highway, fishing harbour facilities and coastal flooding. In addition, typhoon induced strong wind and storm surge increase the scale of damages. The duration of such typhoon-induced extreme ocean-meteorological conditions is not long (~1 day) but the destructive power is very large. Considering the enhancement of global warning, the impacts may be more critical especially when adding the influence of sea level rise. Currently the eastern Taiwan is the main attraction area for tourists. Flooding or damages on coastal highway and facilities of oceanic activities will serious damage the tourism industry. To monitor and forecast the extreme sea impacts and then to build up the warning system is nowadays a very important issue for TWEC. Analysis of field data and the
numerical simulations are both required for assessing the risk of damages.
The purpose of this case study site is to assess the risk of frequent occurred coastal disasters in this area including flooding, overtopping, dyke or coastal highway damages, under the impacts of extreme typhoon induced loadings. These disasters have different causes. Most of them occur due to joint effect of variance natural impacts such as wave, wind, sea level and rains. Study on joint probability of two (or more) impact factors is needed. The risk of damage can be assessed by the joint probability according to different criteria. To achieve the goal, following research items need to be implemented:
- Analysis of field measurements during typhoons (~15 years, ~12 marine buoys, ocean-meteorological database from more than 100 typhoons);
- Simulation of long-term typhoon waves (>50 years);
- Distribution of max. typhoon generated ocean-meteorological elements such as waves, winds, and storm surges;
- Establishment of bivariate model for joint probability analysis (wave+storm surge; wave+wind), both from field and simulated data;
- Uncertainty and risk assessments on frequent damage types at the TWEC.
Results from study site TWEC will bring valued data for proposing the adaptive risk management strategies which is the goal of PEARL. The consideration of joint effects by multi-factors for assessing the coastal risk is an innovation approach and matches PEARL’s research schemes. Experiences from TWEC will significantly increase the range of PEARL researches especially for typhoon-generated extreme impacts. On the other hand, adaptive strategies suggested by PEARL can be disseminated in non-EU country.