Abstract
In previous studies, an emphasis on the particular vulnerability of small island states to future sea-level rise and the intensity of increasing storm surges have been discussed. This preliminary assessment develops a Coastal Vulnerability Index (CVI) along the 202 km-long coastline of Ngazidja Island (formerly Grande Comore, Comoros Archipelago), using fieldwork, remote sensing, and geographic information system tools (GIS). The CVI considers nine variables: geology (a), geomorphology (b), topography (c), shoreline change (d), shoreline exposure (e), relative sea-level rise (f), significant wave height (g), mean tide range (h), and land-use (i). The land-use variable was added in this analysis to highlight the human asset exposure in the surrounding areas. Each variable was ranked based on local physical and hydrodynamic conditions and their vulnerability contribution to sea-level rise. The CVI was computed in 270 sections. According to the vulnerability index, approximately 57.5% of the coastline is under low and moderate vulnerability. High and very high vulnerabilities refer specifically to beaches and shores with old volcanic lava flows located mainly in the northern, northeastern, and southeastern parts of the island, approximately 42.5% of the coastline. The lowest value of CVI is 9.2 on high, rocky cliffs and the highest value is 160 on beaches. This vulnerability partition along the coastline is consistent with in situ indicators of coastal erosion and flooding. In a sea-level rise context, it is of prime importance to integrate coastal vulnerability maps with planning and sustainable management of the coastal zone.
Similar content being viewed by others
References
Abuodha PAO, Woodroffe CD (2010) Assessing vulnerability to sea level rise using a coastal sensitivity index: a case study from Southeast Australia. J Coast Conserv 14:189–205. https://doi.org/10.1007/s11852-010-0097-0
Anderson TR, Fletcher CH, Barbee MM, Frazer LN, Romine BM (2015) Doubling of coastal erosion under rising sea level by Mid-Century in Hawaii. Nat Hazards 78:75–103. https://doi.org/10.1007/s11069-015-1698-6
Arun Kumar A, Kunte PD (2012) Coastal vulnerability assessment for Chennai, East coast of India using geospatial techniques. Nat Hazards 64:853–872. https://doi.org/10.1007/s11069-012-0276-4
Bachèlery P, Coudray J (1993) Carte volcano-tectonique de la Grande Comore (1:50,000). Laboratoire de cartographie, Montpellier: CIRAD-CA. https://agritrop.cirad.fr/483016/
Betzold C, Mohamed I (2017) Seawalls as a response to coastal erosion and flooding: a case study from Grande Comore, Comoros (West Indian Ocean). Reg Environ Changement 17:1077–1087
Cazenave A, Berthier E, Meyssignac B, Le Cozannet G, Masson-Delmotte V (2015) Sea level variations: past, present and future. Meteorologie 88:69–82. https://doi.org/10.4267/2042/56363
Di Paola G, Aucelli PPC, Benassai G, Iglesias J, Rodríguez G, Rosskopf CM (2018) The assessment of the coastal vulnerability and exposure degree of Gran Canaria Island (Spain) with a focus on the coastal risk of Las Canteras Beach in Las Palmas de Gran Canaria. J Coast Conserv 22:1001–1015. https://doi.org/10.1007/s11852-017-0574-9
Ferrario F, Beck MW, Storlazzi CD, Micheli F, Shepard CC, Airoldi L (2014) The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nat Commun 5:3794. https://doi.org/10.1038/ncomms4794
Freed S, Granek EF (2014) Effects of human activities on the World’s most vulnerable coral reefs: Comoros case study. Coast Manag 42:280–296. https://doi.org/10.1080/08920753.2014.904261
Hauzer M, Dearden P, Murray G (2013) The fisherwomen of Ngazidja Island, Comoros: fisheries livelihoods, impacts, and implications for management. Fish Res 140:28–35. https://doi.org/10.1016/j.fishres.2012.12.001
Head CEI, Bayley DTI, Rowlands G, Roche RC, Tickler DM, Rogers AD, Koldewey H, Turner JR, Andradi-Brown DA (2019) Coral bleaching impacts from Back-to-Back 2015–2016 thermal anomalies in the remote central Indian Ocean. Coral Reefs 38:605–618. https://doi.org/10.1007/s00338-019-01821-9
Hereher M, Al-Awadhi T, Al-Hatrushi S, Charabi Y, Mansour S, Al-Nasiri N, Sherief Y, El-Kenawy A (2020) Assessment of the coastal vulnerability to sea level rise: Sultanate of Oman. Environ Earth Sci 79:369. https://doi.org/10.1007/s12665-020-09113-0
Hinkel J, Brown S, Exner L, Nicholls RJ, Vafeidis AT, Kebede AS (2012) Sea-level rise impacts on Africa and the effects of mitigation and adaptation: an application of DIVA. Reg Environ Change 12:207–224. https://doi.org/10.1007/s10113-011-0249-2
Hughes TP, Kerry JT, Simpson T (2018) Large-scale bleaching of corals on the Great Barrier Reef. Ecology 99:501–501. https://doi.org/10.1002/ecy.2092
Islam MA, Hossain MS, Murshed S (2015) Assessment of coastal vulnerability due to sea level change at Bhola Island, Bangladesh: using geospatial techniques. J Indian Soc Remote Sens 43:625–637. https://doi.org/10.1007/s12524-014-0426-0
Jana S (2020) Micro-level coastal vulnerability assessment in relation to post-Aila landscape alteration at the fragile coastal stretch of the Sagar Island. India Reg Stud Mar Sci 33:100908. https://doi.org/10.1016/j.rsma.2019.100908
Koroglu A, Ranasinghe R, Jiménez JA, Dastgheib A (2019) Comparison of coastal vulnerability index applications for Barcelona Province. Ocean Coast Manag 178:104799
López Royo M, Ranasinghe R, Jiménez JA (2016) A rapid, low-cost approach to coastal vulnerability assessment at a national level. J Coast Res 32:932–945
Mahabot M, Pennober G (2015) Rapport Final POCTOI UMR ESPACE DEV 20–30 Septembre 2014. 33 p
Malherbe J, Engelbrecht FA, Landman WA (2013) Projected changes in tropical cyclone climatology and landfall in the southwest Indian Ocean region under enhanced anthropogenic forcing. Clim Dyn 40:2867–2886. https://doi.org/10.1007/s00382-012-1635-2
Mclaughlin S, Cooper JAG (2010) A multi-scale coastal vulnerability index: a tool for coastal managers? Environ Hazards 9:233–248. https://doi.org/10.3763/ehaz.2010.0052
McLeman R (2018) Migration and displacement risks due to mean sea level rise. Bull Atomic Sci 74:148–154. https://doi.org/10.1080/00963402.2018.1461951
Meetoo C (2014) Étude des conditions de cyclogenèse tropicale sur le sud-ouest de l’Océan Indien. Dissertation, University of Toulouse III Paul Sabatier
Michon L (2016) The volcanism of the Comores archipelago integrated at a regional scale. In: Bachèlery P, Lénat J-F, Di Muro A, Michon L (eds) Active volcanoes of the southwest Indian Ocean: and Karthala. Active volcanoes of the World. Springer, Berlin
Ng K, Borges P, Phillips MR, Medeiros A, Calado H (2019) An integrated coastal vulnerability approach to small islands: the Azores case. Sci Total Environ 690:1218–1227. https://doi.org/10.1016/j.scitotenv.2019.07.013
Nurhuda A, Mubarak M, Sutikno S (2019) Analysis of coastal vulnerability of Rangsang Island due to climate changes. J Degrade Min Land Manage 6:1907–1914. https://doi.org/10.15243/jdmlm.2019.064.1907
Péquignet AC, Becker JM, Merrifield MA, Boc SJ (2011) The dissipation of wind wave energy across a fringing reef at Ipan, Guam. Coral Reefs 30:71–82. https://doi.org/10.1007/s00338-011-0719-5
Ratter BMW, Petzold J, Sinane K (2016) Considering the locals: coastal construction and destruction in times of climate change on Anjouan, Comoros. Nat Resour Forum 40:112–126
Ružić I, Dugonjić Jovančević S, Benac Č, Krvavica N (2019) Assessment of the coastal vulnerability index in an area of complex geological conditions on the Krk Island. Northeast Adriatic Sea Geosci 9:219. https://doi.org/10.3390/geosciences9050219
Sahana M, Hong H, Ahmed R, Patel PP, Bhakat P, Sajjad H (2019) Assessing coastal island vulnerability in the Sundarban biosphere Reserve, India, using geospatial technology. Environ Earth Sci 78:304. https://doi.org/10.1007/s12665-019-8293-1
Shaw J, Taylor RB, Forbes DL, Ruz M-H, Solomon S (1998) Sensitivity of the Canadian coast to sea-level rise. Geol Surv Can Bull. https://doi.org/10.4095/210075
Tano RA, Aman A, Kouadio KY, Toualy E, Ali KE, Assamoi P (2016) Assessment of the Ivorian coastal vulnerability. J Coast Res 32:1495–1503
Thieler ER, Hammar-Klose ES (1999) National assessment of coastal vulnerability to sea-level rise, US Atlantic coast, Open-File Report no. 99593, 1 sheet. United States Geological Survey, Woods Hole
Thieler ER, Hammar-Klose ES (2000) National assessment of coastal vulnerability to sea-level rise: preliminary results for the US. Pacific Coast, Open-File Report 00–178, 1 sheet. United States Geological Survey
Turvey R (2007) Vulnerability assessment of developing countries: the case of small-island developing states. Dev Policy Rev 25:243–264. https://doi.org/10.1111/j.1467-7679.2007.00368.x
Walsh KJE, McBride JL, Klotzbach PJ, Balachandran S, Camargo SJ, Holland G, Knutson TR et al (2016) Tropical cyclones and climate change. Wiley Interdiscip Rev Clim Change 7:65–89. https://doi.org/10.1002/wcc.371
Yin J, Yin Z, Wang J, Xu S (2012) National assessment of coastal vulnerability to sea level rise for the Chinese Coast. J Coast Conserv 16:123–133. https://doi.org/10.1007/s11852-012-0180-9
Zhou Y, He B, Xiao F, Feng Q, Kou J, Liu H (2019) Retrieving the lake trophic level index with Landsat-8 Image by atmospheric parameter and RBF: a case study of lakes in Wuhan. China Remote Sens 11:457. https://doi.org/10.3390/rs11040457
Acknowledgements
We would like to thank the three anonymous reviewers who provided very insightful comments and suggestions that greatly strengthened our manuscript. Also, we would like to show our gratitude to the Alliance Mondiale contre le Changement Climatique (AMCC) in the Comoros for providing their aerial photographs that have permitted us to have a general overview of coastal geomorphology and land-use.
Funding
No funding was received for conducting this study.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Mahamoud, A., Gzam, M., Ahmed Mohamed, N. et al. A preliminary assessment of coastal vulnerability for Ngazidja Island, Comoros Archipelago, Western Indian Ocean. Environ Earth Sci 81, 44 (2022). https://doi.org/10.1007/s12665-021-10136-4
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s12665-021-10136-4