Coastal Vulnerability Assessment Based on Multi-Hazardous Events. Case study: Northwestern Coastline of Guinea-Bissau (NC-GB)

Guinea-Bissau coastlines are found highly vulnerable to coastal hazards, and this vulnerability will likely increase under future climate changes scenarios. In addition, the multi-hazardous assessment studies have not yet been conducted to clarify the status of vulnerability index to coastal hazards. Therefore, we integrated eight bio-geophysical parameters and elaborate a comprehensive Coastal Vulnerability Index to coastal hazards, stablish the rate of sea-level rise and determine the role of coastal habitats in protecting the shorelines in the Northwestern Coastline of Guinea-Bissau, by using the GIS and Coastal Vulnerability Index of InVEST Model. The study found that, out of 87 km of the studied coastlines, nearly 45 km lie in high to very-high vulnerability index. 17 km are found in a moderate vulnerability index and 25 km are found at low to very-low vulnerability index. The main responsible for high vulnerability registered in Zone-B were the wind and wave exposure, as this coastline is highly exposed to sea. The other reason was the storm surge and sea-level that rises 8.79/year, motivated by low coastal elevation. Mangrove ecosystem that are largely found in Zone-A, play very important role in protecting shoreline from coastal hazards with value 0.61, followed by forest and sand dune that are found mostly in Zone-C with 0.49 and 0.4 respectively, and saltmarsh that are relatively found in Zone-B with value 0.32. These findings can assist coastal managers in cost-effective adaptation plans, provide a scientific basis for sustainable coastal management and guidance for ecological conservation in coastal regions.

Coastal Vulnerability Index for Kuwaiti Coast

Kuwait is investing significantly for the development of coastal infrastructures in many of its coastal areas. It is essential to know the vulnerability of the coast of Kuwait for the future sea level rise and other physically influencing parameters. For this purpose, a detailed study is carried out and the Coastal Vulnerability Index (CVI) is established for the Kuwaiti coast including the coasts of Islands. The CVI is assessed based on the data on coastal geomorphology, historical shoreline change rate, landward side of the coastal slope, mean significant wave height, mean tidal range and the particle size of the sediments along the beach. The total Kuwaiti coastline of 499 km is divided into two groups with a total of 162 coastal segments. The group 1 contains 138 segments and covers the mainland, Boubyan and Failaka Island. The group 2 contains 24 locations and covers Umm Al-Maradim, Qaru and Kubbar Islands. Field data collection is carried out for all these segments. From this study it is found that 5% of the Kuwaiti coastal area in group 1 are very low vulnerable; 34% low vulnerable; 31% moderately vulnerable; 18% highly vulnerable and 12% are very highly vulnerable. Similar results are obtained for group 2 coastal segments. The results of this study will be useful while preparing the Integrated Coastal Zone Management plan for Kuwaiti coast and for its sustainable coastal infrastructure development.

Towards Efficient Assessment of Coastal Vulnerability to Sea Level Rise

Vulnerability is a compact term that represents an accumulative range of exposure, sensitivity and resilience of a system against both internal and external hazards. In light of this conceptual diagnosis, vulnerability assessment studies can measure the degree of a gap in which the system is vulnerable against various hazards by customizing a quantitative model while qualitative model studies indicate gap points. The results of quantitative models vary according to the adopted formula and the customized parameters. The study aims to improve the efficiency of the "coastal vulnerability index (CVI)" method which is used to assign degrees of coastal vulnerability to sea level rise (SLR). The study is using a comparative analytical approach to empirically assess the vulnerability of the African coast to SLR based on a selected group of physical and socioeconomic parameters (seventeen parameters). Although the first model, based on a formula of the square root of product mean and the second model, based on a formula of average of the square root of product sum, have a positive correlation with semistrong relation (+ 0.65), their results are varied. It is found that the first model is used when there is a dominant parameter in the study while the second model is used when there is an equality between parameter weights. Topography associated with proximity to the coast is a dominant factor when assessing the vulnerability of an area to SLR threat.

The Importance of Geotechnical Evaluation and Shoreline Evolution in Coastal Vulnerability Index Calculations

The aim of this specific study is to present a new weighted Coastal Vulnerability Index (CVIWF), with an emphasis given to the geotechnical evaluation and shoreline evolution rate measured through high-resolution remote sensing, which seem to be the most interfering variables in CVI calculations. As a pilot area for the application of the new CVIWF, the Gulf of Patras in Western Greece was selected, which is suffering erosion problems due to climate change, the sea level rising and human intervention. The new CVIWF, which was applied in this research, includes the following innovations: (1) the use of geotechnical characterization instead of geological–geomorphological characterization, (2) the use of high-resolution remote sensing data for the detection of shoreline evolution rate and (3) the insertion of a specific weighted geotechnical factor in the CVIWF formula. The results from the application of the unweighted CVI show that percentages of 20.13%, 20.47%, 24.56%, 29.39% and 5.45% of the gulf’s shoreline are under the regime of very low, low, moderate, high and very high vulnerability, respectively. On the other hand, the corresponding results from the application of the weighted CVIWF show a percentage of 14.59%, 25.91%, 20.04, 36.48% and 2.98, respectively.

TINGKAT KERENTANAN PESISIR DI UTARA DAN TIMUR PULAU BINTAN PROVINSI KEPULAUAN RIAU TAHUN 2020

Wilayah pesisir sangat unik, dinamis, dan kompleks karena merupakan zona interaksi antara daratan, lautan, dan atmosfer. Hal ini menjadikan wilayah pesisir sebagai wilayah yang paling rentan di Bumi. Untuk mengetahui seberapa besar kerentanan di suatu wilayah pesisir, perlu dilakukan penelitian untuk mengetahui tingkat kerentanan wilayah pesisir dan faktor yang mempengaruhi. Penelitian mengenai tingkat kerentanan pesisir di lokasi ini pernah dilakukan pada tahun 2016 dan diperoleh simpulan bahwa tingkat kerentanan pesisir berada pada kategori sedang. Dengan semakin berkembangnya pemanfaatan potensi di daerah tersebut maka dirasa perlu dilakukan penelitian serupa dengan tahun 2016 untuk mengetahui apakah terdapat perubahan tingkat kerentanan antara tahun 2016 dengan tahun 2020. Data-data yang digunakan terdiri dari Data-data yang digunakan terdiri dari geomorfologi pantai, pasang surut, citra satelit Landsat 7 ETM+ dan 8 OLI, kenaikan muka laut dan DEM. Analisis data menggunakan metode Coastal Vulnerability Index (CVI). Hasil penelitian menunjukkan tingkat kerentanan pesisir di lokasi penelitian berada pada kategori rendah-sedang, dengan kisaran skor CVI 9,93-25,86. Topografi, geomorfologi, intensitas perubahan garis pantai, dan kemiringan pantai merupakan faktor yang dapat menyebabkan tingkat kerentanan di lokasi penelitian menjadi sangat tinggi. Namun, keterhubungan antara parameter lain yang dapat menjadi faktor penghambat tingginya tingkat kerentanan, menyebabkan tingkat kerentanan pesisir di lokasi penelitian hanya berada dalam kategori rendah-sedang. Terdapat perubahan kondisi tingkat kerentanan antara tahun 2016 dengan tahun 2020 dimana pada tahun 2020 tingkat kerentanan di pantai timur mengalami penurunan menjadi kategori rendah.

Alarming coastal vulnerability of the deltaic and sandy beaches of North Africa

The arid coasts of North Africa, extending over 4633 km from the Gulf of Tunis to the Nile Delta, are undergoing pronounced shoreline retreats and coastal floodings that are reported as a consequence of the ongoing sea level rise resulting from global warming. Of particular interest are the abnormal shoreline dynamics for deltaic and sandy beaches, which are severely impacted by abrupt decadal variabilities in both climatic and anthropogenic drivers resulting in their increased vulnerability to disturbances from coastal hazards. Unfortunately, the evolution, distribution and impacts of these drivers remain largely unquantified, let alone understood, for these extensive arid coasts that harbor the major portion of North Africa’s population as well as unique and fragile marine ecosystems. To address this deficiency, we use GIS-based multi-criteria approaches combined with analytic hierarchy process to map the Coastal Vulnerability Index and the Socioeconomic Vulnerability Index along these coasts to investigate the amplitude and extent of shoreline deterioration resulting from sudden fluctuations in sediment transport to the coastline. We use the western bay of the Gulf of Tunis, the coasts of Tripoli and the Nile Delta as three validation sites for our vulnerability assessment. The statistical Integrated Coastal Vulnerability Index map reveals that 47% of arid North African coasts are characterized by high to very high vulnerability. In particular, we observe that the densely populated deltaic coasts in both Tunisia and Egypt are 70% more vulnerable than any others coast in the eastern Mediterranean Basin. These abnormally high-vulnerability extensive areas are also correlated with significant deterioration of coastal aquifers and hence in crop production, compromising local food security and resulting in increasing outflow migration trends. Both Tunisia and Egypt observed dramatic increases in the net population outflow migration by respectively 62% and 248% between 2000 and 2016, mostly from coastal areas. Our source analysis of the amplitude and extent of these high coastal vulnerabilities suggests that they result from the anthropogenic drivers of damming and rapid urban growth over the last few decades rather than the effects of global warming.