Major natural hazards in a tropical volcanic island: A review for Mayotte Island, Comoros archipelago, Indian Ocean

Audru, J.; Bitri, Adnand; Desprats, Jean‐François; Dominique, Pascal; Eucher, Guillaume; Hachim, Said; Jossot, Olivier; Mathon, Christian; Nédellec, Jean-Louis; Sabourault, Philippe; Sedan, Olivier; Stollsteiner, Philippe; Terrier-Sedan, Monique

doi:10.1016/j.enggeo.2010.05.014

Cited by 25 publications

(16 citation statements)

References 50 publications

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“…Geographic location and reef geomorphology were the most significant drivers of the observed patterns in the structure of reef fish assemblages across the WIO, based on density and biomass data suggesting that historic large-scale geological processes (e.g., Audru et al, 2010;Obura, 2015) are major drivers in structuring coral reef fish assemblages in this region. Other biogeographic processes may also explain the patterns, though our survey sites cannot be seen as representative of each country as a whole, particularly Madagascar.…”

Section: Geographic Patterns In Fish Assemblagesmentioning

confidence: 99%

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Samoilys

Halford

Osuka

2019

Ecology and Evolution

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Aim Understanding the drivers of the structure of coral reef fish assemblages is vital for their future conservation. Quantifying the separate roles of natural drivers from the increasing influence of anthropogenic factors, such as fishing and climate change, is a key component of this understanding. It follows that the intrinsic role of historical biogeographical and geomorphological factors must be accounted for when trying to understand the effects of contemporary disturbances such as fishing. Location Comoros, Madagascar, Mozambique and Tanzania, Western Indian Ocean (WIO). Methods We modeled patterns in the density and biomass of an assemblage of reef‐associated fish species from 11 families, and their association with 16 biophysical variables. Results Canonical analysis of principal coordinates revealed strong country affiliations of reef fish assemblages and distance‐based linear modeling confirmed geographic location and reef geomorphology were the most significant correlates, explaining 32% of the observed variation in fish assemblage structure. Another 6%–8% of variation was explained by productivity gradients (chl_ a ), and reef exposure or slope. Where spatial effects were not significant between mainland continental locations, fishing effects became evident explaining 6% of the variation in data. No correlation with live coral was detected. Only 37 species, predominantly lower trophic level taxa, were significant in explaining differences in assemblages between sites. Main Conclusions Spatial and geomorphological histories remain a major influence on the structure of reef fish assemblages in the WIO. Reef geomorphology was closely linked to standing biomass, with “ocean‐exposed” fringing reefs supporting high average biomass of ~1,000 kg/ha, while “lagoon‐exposed fringing” reefs and “inner seas patch complex” reefs yielded substantially less at ~500kg/ha. Further, the results indicate the influence of benthic communities on fish assemblages is scale dependent. Such insights will be pivotal for managers seeking to balance long‐term sustainability of artisanal reef fisheries with conservation of coral reef systems.

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Section: Geographic Patterns In Fish Assemblagesmentioning

confidence: 99%

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Samoilys

Halford

Osuka

2019

Ecology and Evolution

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“…Mayotte, the southernmost island in the Comoros archipelago, with a surface area of 374 km 2 , is a French Overseas Department with about 200 000 inhabitants. It faces an exponential increase in its water needs because of both population growth – a fourfold increase in less than 30 years (Audru et al ., ) – and the progressive access to a better standard of living. Formerly, Mayotte relied mostly on surface water and a desalination plant (now supplying less than 5%), in addition to a few springs and large‐diameter low‐discharge alluvial wells.…”

Section: Introductionmentioning

confidence: 99%

High‐resolution conceptual hydrogeological model of complex basaltic volcanic islands: a Mayotte, Comoros, case study

et al. 2014

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International audienceWe present a high-resolution conceptual hydrogeological model for complex basaltic volcanic islands based on Mayotte Island in the Comoros. Its geological structure and hydrogeological functioning are deduced from a large dataset: geological mapping, geophysics, some forty new boreholes, piezometric data, hydraulic conductivity, hydrochemical data, etc. We describe previously unknown deep cut-and-fill palaeovalleys. The resulting conceptual geological and hydrogeological model of the island is very different from the Hawaiian model, in that it lacks a low-elevation basal aquifer and dyke-impounded high-level aquifers. It is closer to the Canary Islands model, which has, however, not yet been described at a high-resolution scale. It does not have a continuous aquifer, but rather a discontinuous succession of perched aquifers separated by aquicludes and aquitards. This results more from the complex geological structure of the island, which has experienced several phases of volcanism, erosion and weathering, than from its age, but is also a result of the high-resolution scale of the model. High-resolution conceptual modelling is now necessary to solve problems of applied geology and hydrogeology

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“…Coastal areas are also subjected to multihazards ie flooding, storm surge, rising sea level and coastal erosion from tropical storms and hurricanes. Multihazard approach should be taken for these areas as noted by Audru et al [2010] in creating multihazard map for Mayotte island. The IPCC 2007 report shows an increase of 1.5 o C of temperature in the Caribbean leading to seal level rise, storm surge and flooding.…”

Section: Discussionmentioning

confidence: 99%

“…However absence of gauging stations and historical flood marks for some of the low lying coastal towns ie Port Maria makes it difficult to create flood hazard maps for such areas. Audru et al [2010] outlines uses of alternative methodologies for creating hazard maps in areas where absence of past flood marks, caused reservations in creating flood hazard maps for the small (< 25 km 2 ) watershed of Mayotte island in the Indian ocean. Hazard levels for the island was based on water depths and velocity during floods and calibrated with intense rain events.…”

Section: Introductionmentioning

confidence: 99%

Flooding in Jamaica with assessment of riverine inundation of Port Maria, St Mary

Mandal

Maharaj

2013

Bulletin De La Société Géologique De France

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Flash flooding, from extreme rainfall is one of the major natural disasters affecting Jamaica and other small island states of the Caribbean. Flooding in Jamaica is mainly riverine, coastal and depression with the major coastal towns being affected owing to their location on low lying areas. Such localization is driven by increase in urbanization and tourism along the coastal areas. The present work aims in a broad discussion of the flooding in Jamaica with special reference to riverine flooding of Port Maria, the capital of St Mary, one of the parishes lying in the high rain zone of the island and being affected by repeated events of flooding. Analysis of the extreme rainfall event of November 23 rd -24 th , 2006 shows that it exceeded the 30 yr annual rainfall of the area and the 100 yr return period as calculated from 30 yr annual rainfall data for the island. The Port Maria river lacks a gauging station to monitor flow data and flood discharge peaks. Several methods are used to calculate the run-off in such small ungauged catchments. In this study the Soil Conservation Systems Curve Number (CN) method was used to calculate the run-off from the measured rainfall data using empirical equations. Results show an unprecedented high of 13-14 inches affecting the buildings and other infrastructures, leading to the collapse of a newly constructed bridge over the river Port Maria. The town continues to get flooded from intense short duration rainfall continuing to affect life and property. Flood plain maps exist for the larger watersheds of the island but smaller yet flood prone ones have not been mapped so far. Hence this becomes very important to create a floodplain map showing the extent of the runoff from rainfall with respect to the buildings and other infrastructures of the area. The present work thus aims in creating a spatial distribution map of the runoff from the rainfall measurements aiding in developing a no build zone for this and for other low lying coastal areas of the island.

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Major natural hazards in a tropical volcanic island: A review for Mayotte Island, Comoros archipelago, Indian Ocean

Cited by 25 publications

References 50 publications

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

High‐resolution conceptual hydrogeological model of complex basaltic volcanic islands: a Mayotte, Comoros, case study

Flooding in Jamaica with assessment of riverine inundation of Port Maria, St Mary

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