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12/13, 2023, 10:00 am (UTC+8)

Speaker: Prof. Wei-Po, Huang (National Taiwan Ocean University, Taiwan)(CV)

Title: The Comprehensive Coastal Hazard Analysis and Risk Governance for the Small Natural Islands Surrounding Taiwan

Abstract: 

 According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (IPCC, 2021), the assessment of hazard risk governance still indicates the high confidence of challenge in Asia because of the incomplete governance mechanism. In Taiwan, coastal erosion is not only a ubiquitous hazard within the coastline but one of the coastal statutory hazards. However, these small islands have fewer survey data and are less developed than the main island of Taiwan. Under the threat of climate change, coastal erosion is occurring on these small islands, and these small islands are more vulnerable to unknown risks under the incomprehensive hazard analysis database and governance mechanism. Therefore, it is urgent to quantify the coastal erosion hazard and risk to compensate for the absence of risk perception for the coastal authority and stakeholders, and to propose the proper risk adaptive measure and the interface coordination between the coastal departments. Within the hazard analysis, the analysis of shoreline change trends has become a vital coastal management tool as the population of islands grows and the demand for coastal land increases. However, as previously stated, there is a notable scarcity of monitoring data for these small islands, rendering a precise assessment unfeasible. Due to its affordability and the abundance of historical information, satellite imagery is one of the most valuable data sources for the assessment. In this study, the long-term and the short-term trends of beach topography changes by using satellite images and aerial photographs were assessed. An open-source software toolkit, CoastSat, is used to obtain time-series shoreline positions from satellite images. The historical shorelines can be determined by using a Neural Network classifier to classify each pixel in the image into the following four categories: 'sand', 'water', 'white-water', and 'other land features'. In order to derive the 0m isobaths, the trigonometric relationships are used to alter the instantaneous waterline based on the measured coastal slope and water level elevation. All in all, the shoreline change analysis quantifies the hazard potential on the sector of small natural islands, and the result is informative for risk assessment and governance. In terms of risk assessment, this study considers risk identification, risk classification, and risk evaluation to quantify the integrated hazard and vulnerability index. In the risk identification, the Fuzzy Delphi Method is employed to calculate the consensus value and the importance of each hazard and vulnerability factor to select the representative factors. Three commonly used classification methods are applied in the construction of the coastal hazard and vulnerability index: Qualitative analysis, quantitative analysis, and semi-quantitative analysis. This study calculates the weight relationships between representative factors via the Analytic Hierarchy Process in the risk evaluation. According to the division of authority department, the adaptive measure is proposed to improve the hazard and vulnerability risk respectively in the risk treatment. Simultaneously, the governance countermeasures are discussed based on the risk assessment. Under the proposed adaptive measure, the representative factors and origins of risk in the study area are clarified and quantified, thus indicating new priorities for resource allocation. Moreover, the competent authority of coastal risk governance management is precisely divided and collaborated which is more resilient to climate change. 

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12/19/2023, 10:00 (UTC+8)

Speaker: Dr. Wenjie Sun ( Institute of Geology and Geophysics, Chinese Academy of Sciences, China)(CV)

Title:  The spatial features of Es and E-region irregularities in East/Southeast Asia based on the IONISE network
Abstract:
The recently built Ionospheric Observational Network for Irregularity and Scintillation in East/Southeast Asia (IONISE), which mainly includes three chains of GNSS TEC/scintillation receivers along 110°E, 23°N, and 40°N respectively, multi-static portable digital ionosondes, VHF radars, and all-sky radars, provides a good data set for the study on ionospheric irregularities. Based on IONISE and other GNSS networks around China, the morphology of sporadic E (Es) structures and E-region irregularities were investigated. It is revealed that the strong Es layer could elongate 1000–3000 km as large-scale band-like structures. The main onset region for the large-scale Es structures over China was identified for the first time, which is around 20°–45°N and 100°–125°E. Further, based on the all-sky radar interferometry observations, the spatial features of E-region irregularities at low latitudes were obtained. The continuous type E-region irregularities were observed being generated locally without obvious zonal drift. The QP type generally covered ~40-500 km zonally, and consisted of up to 9 (peaking at 3-4) irregularity patches separated by ~20-130 km (peaking at ~60 km). A unique case of wavelike structure of E region irregularities elongating more than 200 km zonally was also presented. It is suggested that gravity waves could play an important role in modulating the spatial features of Es and E-region irregularities.