Sunday, November 27, 2011

Beach Profiling With the International School

It is certainly an interesting time of year to be beach profiling at Beau Vallon! Now that the North West monsoon season has arrived the sea in Beau Vallon Bay has become pretty rough and the beach is beginning to change shape quite dramatically.

Georgia explaining how to set up the beach profile

Today Georgia French (Project Coordinator) and Uzice Samedi (Researcher) took a group of 20 students from the International School on a beach profiling trip to teach them the methods behind the technique. Beach profiling is used to measure the slopes of different sections of the beach. MCSS profiles several beaches every month so that we can see how the beaches are changes in shape over time.This is important for nesting turtles as the shape of the beach effects how easy it is for female turtles to crawl up it to lay their eggs. For example, erosion of the sand by the sea can cause erosion cliffs to form (demonstrated in section B to C in the diagram below) which can be impossible for turtles to climb.

Erosion can also wash away sections of the beach that turtles have already laid in, destroying their nests. However, beaches are not constantly eroding, there is also sand accretion where sand is deposited on the beach, making it bigger. It all depends on the monsoon season and if any coastal engineering has been undertaken on or near a beach. Coastal engineering can include building sea walls, jetties and groins. These structures change the way that the sea water moves around a shore line and so effects how sand is eroded or accreted.

To measure the beach profile, you need two ranging poles, an Abney Level, a measuring tape, data forms and pencils. Clipboards are very helpful when it is windy as it was today! Each section of the beach is measured and using the poles and Abney level, it is possible to measure the slope (in degrees and minutes) of each beach section. If a section of the beach is flat, the Abney level will read zero degrees, if it sloping down the Abney level will give a negative reading in degrees and minutes and so on.

Two students get to grips with the Abney level

The information gathered on the beach is then put into our beach profile software which produces graphs of the beach profile for us. MCSS will hopefully be starting a new project on coastal erosion in the coming year funded by Mangroves For the Future. This will enable us to get new hi-tech equipment and software that will give us a much better idea of sand movement patterns around Mahé which will allow us to give good advice to coastal managers and developers.
The team hard at work profiling Beau Vallon beach

Everybody did a great job at the measuring today and it was lovely to see everyone helping each other out. Special thanks has to go to those brave enough to hold the pole at the last point of the profile as this was in the sea!

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