Natural Hazards

, Volume 83, Issue 1, pp 601–640

Assessing the impacts of and resilience to Tropical Cyclone Bejisa, Reunion Island (Indian Ocean)

  • V. K. E. Duvat
  • A. K. Magnan
  • S. Etienne
  • C. Salmon
  • C. Pignon-Mussaud
Original Paper

DOI: 10.1007/s11069-016-2338-5

Cite this article as:
Duvat, V.K.E., Magnan, A.K., Etienne, S. et al. Nat Hazards (2016) 83: 601. doi:10.1007/s11069-016-2338-5

Abstract

This paper highlights the high variability of the nature and severity of the impacts of Tropical Cyclone Bejisa (January 2014, category 3) along the 20-km-long beach–dune systems of the western coast of Reunion Island. Erosional impacts were reported on 17 out of 26 topographic transects, while nine transects exhibited accretion. Sediment loss and gain reached maximum average values of 1.23 and 0.36 m3/m of transect, respectively. Sediment deposition occurred on upper beaches and foredunes, which gained up to 1 m in thickness. After 1 year, beach resilience proved to be medium (from 0.4 to 0.8 m3/m) to high (>0.8 m3/m) on 40 % of transects, but some transects exhibited permanent dune loss. Marine inundation reached a maximum distance of 70.8 m from the vegetation line and a maximum elevation of 6.9 m above sea level. The indigenous vegetation showed high resistance to the impacts of the cyclone and rapid regeneration, whereas introduced species were lastingly damaged. The cyclonic waves damaged 18 seawalls protecting either public infrastructures or private properties, half of which had been reconstructed 3 months later. Severe damage was also caused to a marina built in the downstream section of a river. Importantly, this study emphasises the vicious-cycle effects caused by “coastal compression” that exacerbates the devastating impacts of cyclonic waves on beaches, vegetation and protection structures, encouraging coastal residents to strengthen engineered structures. In accretional areas, the reworking of sediment deposits by residents reduced the long-term benefits of sediment deposition. Such human-induced processes increase asset exposure and vulnerability.

Keywords

Tropical cyclones Coastal risks Resilience Beach–dune systems Small islands Indian Ocean 

Supplementary material

11069_2016_2338_MOESM1_ESM.eps (1.8 mb)
ESMF 1Topographic profiles P2 (a), P3 (b) and P4 (c), Saint-Paul Bay, sediment cell 1 (see location on Fig. 6). These three beach profiles show the erosional impacts of TC Bejisa on the beach-dune system of Saint-Paul Bay and the contrasting responses of the dune and beach, the former showing limited or no resilience, whereas the latter proves to be resilient. (EPS 1807 kb)
11069_2016_2338_MOESM2_ESM.eps (1.7 mb)
ESMF 2Topographic profiles P5 (a), P6 (b) and P8 (c), Boucan Canot Beach, sediment cell 3 (see location on Fig. 6). These three beach profiles show the marked erosional impacts of TC Bejisa on the beach-dune system of Boucan Canot Beach and the unequal resilience of the beach during the year following the event. Profile 8 (c) shows that the cyclonic waves destroyed a seawall that was rapidly rebuilt by residents after the event (see photographs e and f, Fig. 16). This narrow section of the beach is less resilient than its much wider northern section. (EPS 1779 kb)
11069_2016_2338_MOESM3_ESM.eps (2.8 mb)
ESMF 3Topographic profiles P10 (a), P11 (b) and P12 (c), Cap Homard Beach, sediment cell 4 (see location on Fig. 6). These profiles show the marked erosional impacts of TC Bejisa on the narrowest central (b) and southern (c) parts of Cap Homard Beach that exhibited limited resilience during the year following the cyclone. (EPS 2912 kb)
11069_2016_2338_MOESM4_ESM.eps (1.6 mb)
ESMF 4Topographic profiles P16 (a), P17 (b) and P18 (c), Ermitage Beach, sediment cell 6 (see location on Fig. 6). Profiles 16 (a) and 17 (b) illustrate the contrasting impacts of TC Bejisa in built and non-built areas: profile 16 shows the marked and long-lasting erosional impacts of TC Bejisa on coastal sections that have a narrow beach bordered by seawalls, highlighting the role of vertical structures in generating sediment loss; on the contrary, profile 17 shows that natural sand-dune systems are both less impacted by cyclonic waves and more resilient to their impacts. Profile 18 (c) illustrates the limited impacts of TC Bejisa on the southern part of the Ermitage-La Saline sediment cell. (EPS 1688 kb)
11069_2016_2338_MOESM5_ESM.eps (1.5 mb)
ESMF 5Topographic profiles P19 (a), P20 (b) and P21 (c), Ermitage-La Saline Beach, sediment cell 6 (see location on Fig. 6). Profile 19 exhibits the accretional impacts of TC Bejisa (+0.3 m3) and the following storms (distant-source swells occurring in April 2014 and TC Bansi, January 2015) on this southern coastal section. Profiles 20 (b) and 21 (c) clearly exhibit the accretional impacts of all three storms. (EPS 1586 kb)
11069_2016_2338_MOESM6_ESM.eps (1.4 mb)
ESMF 6Topographic profiles P22 (a), P24 (b) and P25 (c), Ermitage-La Saline Beach, sediment cell 6 (see location on Fig. 6). Compared to profiles P19, P20 and P21, these southernmost profiles exhibit the accretional impacts of TCs Bejisa (January 2014) and Bansi (January 2015), with sediment gain ranging from +1.3 to +7.9 m3. These results are in accordance with multi-decadal shoreline changes showing coastline advance. (EPS 1472 kb)

Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • V. K. E. Duvat
    • 1
  • A. K. Magnan
    • 2
  • S. Etienne
    • 3
  • C. Salmon
    • 1
  • C. Pignon-Mussaud
    • 1
  1. 1.UMR LIENSs 7266University of la Rochelle-CNRSLa RochelleFrance
  2. 2.Institute for Sustainable Development and International RelationsParisFrance
  3. 3.CNRS, UMR 6554 LETG, EPHEPSL Research UniversityDinardFrance

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