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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: The influence of reefs on coastal oceanography, erosion and recovery

Currently Active: 
Yes

Reefs: Types and distribution Mechanisms through which natural rock and coral reefs interact with waves, currents, sediment transport and morphology were investigated at Yanchep Lagoon in southwestern Australia (Gallop et al, 2011, 2012). Reef elevation relative to sea level determined if, and how much beach erosion and recovery were affected (Fig. 1abc). The alongshoreplacement and continuity of reefs determined trapping of littoral drift; constricted current jets, create local sediment sources and sinks (Fig. 1d); and created erosion ‘hot spots' landward of alongshore gaps in reefs.

Figure 1
Figure 1

The inuence of porosity and submergence of the Great Barrier Reef (GBR) matrix on wave attenuation

The GBR in northeastern Australia is an offshore reef that consists of a reef matrix, created by thousands of individual reefs separated by gaps through which wave energy can propagate into the lagoon (Hardy and Young, 1996). The ratio of individual reefs to gaps can be described as the porosity  of the reef matrix. Little is known about how the porosity of the reef matrix inuences wave attenuation. The magnitude and variability in the reduction of wave height across reefs has implications for sediment transport, coastal engineering and ushing of the lagoon. Therefore, this research is investigating the dependence of the magnitude of wave attenuation across the reef matrix on reef porosity and submergence. Satellite altimetry measurements of significant wave height (Hs) are being analysed from 1992 to 2012; from 5 satellites (Envisat, ERS12, GFO, Jason1 and Topex-Poseidon)

Figure 3
Figure 3

The response of atoll islands to sea level rise and coral reef degradation

Atoll islands are especially vulnerable to climate change and sea level rise (Woodroffe et al., 2007) because they are lowlying; have small land masses and limited freshwater supply. The coral reefs protecting the islands are threatened by climate change and sea level rise. In addition to providing homes for people, atoll islands are home to spectacular wildlife refuges, 100-year old cultures, agricultural and tourism industries and military bases. The aim is to use process-based numerical models to simulate the response of atoll islands to sea level rise, and coral-reef degradation. This will involve simulating scenarios of sea level rise, and coral reef degradation which may: (1) reduce protection of the islands; and (2) reduce the supply of carbonate sediments to maintain the islands (Fig. 3). This will enable assessment of morphological changes to atoll islands with a range of geomorphology, to allow identification pf areas at high risk of erosion, and to see if the new island morphology can support a freshwater lense.

Key Contacts

Dr Shari Gallop

Dr Ivan Haigh

References:

Gallop, S.L., Bosserelle, C., Pattiaratchi, C., Eliot, I., 2011. Rock topography causes spatial variation in the wave, current and beach response to sea breeze activity. Marine Geology 290:29-40;

Gallop, S.L., Bosserelle, C., Pattiaratchi, C., Eliot, I., 2012. The inuence of coastal limestone landforms on storm erosion and recovery of a perched beach. Continental Shelf Research 47: 16-27;

Hardy, T.A., Young, I.R., 1996. Field study of wave attenuation on an o-shore coral reef. Journal of Geophysical Research 101(C6), 14311-14326;

Woodroffe, C.D., Samosorn, B., Hua, Q., Hart, D.E., 2007. Incremental accretion of a sandy reef island over the past 3000 years indicated by component-specific radiocarbon dating. Geophysical Research letters 34, L03602.

Related research groups

Geology and Geophysics
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