Shifting Sands

IMG_0678Beaches are created by tides and currents which bring in sediment and debris; however the tides and currents can also destroy beaches by taking the sediment away.  This movement of sand is natural and varies throughout the year with differing seasons and weather. But one of the most significant threats to beaches is coastal erosion.  Coastal erosion is the removal of material from the coast by wave action, tidal currents and/or the activities of man, usually resulting in a landward retreat of the coastline. It can be seen in the changing pattern of sand and shapes carved into the rocks.  Seychelles is famous for its beaches, with many claiming top awards.  The country’s reliance on the tourism economy largely depends on promoting its image of paradise – gentle surf of turquoise water upon powdery, white, sandy beaches, lined with takamaka trees surrounded by dark granitic rocks.  The sandy beach is also a key part of the coastal ecosystem; the wetlands, mangroves, beach, reef and oceans are all inextricably linked and naturally balanced. Any erosion would therefore negatively impact on both the economy and island ecology of Seychelles.

We love Petite Anse, therefore each month we conduct beach profiling.

FSRS beach profiling transectsBeach profiling measures the changes in the beach contours along profile transects by recording the length and slope.  The profile transects run in a straight line from points behind the beach all the way down to the water line. We have several permanent markers established along the back of the beach which are the starting points for the transects (transects can be seen in the photo to the right). Usually this surveying takes place during low tide so we can measure more of the beach, although the odd strong wave still catches us out and we end up getting a little wet!

The data collected is then transferred into cool graphs, one for each transect.  This allows us to measure long term changes, such as coastal erosion. We see the most changes at the far north of Petite Anse.  Anomalies have included a large influx of coral rubble, strong north-west winds developing a ledge and the breaching of the wetlands through a deep trench at the southern end.  Over time we hope to see the sand coming and going naturally with no cumulative loss or gain of sediment, thereby displaying security of our beach.

Every few months we send this data to the Seychelles Department of Environment to assist with Seychelles coastal conservation.  As development along the coastlines of Seychelles continues to grow, the impact on the shoreline should be carefully monitored and managed to preserve our beautiful beaches.

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