South West Coastal Group

Profile lines are a series of survey lines typically perpendicular to the coast which are monitored to record beach level (height). They provide a snap-shot of the beach profile which can give an indication of the state of the beach. A short steep beach profile often suggests an eroding coast where as a long, shallow beach profile suggests an accreting coast.

The beach profile surveying methodology has remained
largely unchanged, although new age electronic survey instruments and new technology have simplified measurements.

Electronic distance measurers replaced optical theodolites and electronic data recorders replaced
handwritten field books.

In the past Beach profiles were obtained by marking out an imaginary line down the beach from the back of the beach to the waterline. Ranging poles were then placed to mark the line (A & H below)

Survey points at a given distance were chosen along this line, (B,C,D,E,F,G).

At each sample point in turn,the height is measure using a total station or at a basic level a clinometer to take a bearing to

record the slope angle which was recorded to later work out the change in profile. This method is still often used by educational establishments carrying out fieldwork with students.

However with the onset on new technologies profiles can be carried out much quicker using either a hand held GPS receiver or a mounted receiver on an All Terrain Vehicle

The GPS survey systems works by first calculating the exact distance between the receiver and each of the visible satellites. With three or more such measurements its then possible for it to fix its position in all three dimensions.

A single such receiver has an accuracy of within a few metres, however this can be improved upon with the use of a second receiver.When positioned over a known point this second receiver provides corrections, via a radio link, that enable the moving receiver to calculate its true position to within a few centimetres.

Known as differential GPS this method of surveying has revolutionised the techniques used in beach monitoring, and opened up a whole new range of possibilities.

Even the simple cliff post measurements have now been made obsolete through the use of GPS equipment.

Rather than relying upon single point measurements, the surveyor, whilst carrying the GPS receiver, now walks the entire cliff line automatically recording its position as he travels.

Beach profile surveys give an indication of trends in beach sand loss or gain for each profile over time. The information can be fed into a computer package which will plot the data on a graph to show which section of the beach the sand moves in over the years of
survey.

Sand volumes can be calculated for each profile and then graphed over time to determine any trends.

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