Observing swash and backwash, and transport of material

Equipment

  • Float, for example an orange or cork

  • Stopwatch

  • Tape measure

Methodology

  • Decide on an appropriate distance to measure longshore drift over, for example 10 metres

  • Lay out tape measure close to water and mark start and finish points

  • Place your float into water in the breakwater zone at the start point

  • Observe and time the object's movement across the pre-set distance

Similar results can be obtained if the distance travelled by the object is recorded over a specified time, for example five minutes.

Considerations and possible limitations

  • Tidal and wind conditions, the size and weight of float used and the slope angle of the beach may all affect measurements

  • Take note of the wind speed and direction on the day the fieldwork is undertaken as this may affect the speed at which the float is transported. This is particularly important if further sampling for the investigation is undertaken on another day

  • Obstructions to the movement of float, for example rocky outcrops, may affect results.

  • Floats may be lost during the investigation. Repeated experiments or the use of more than one marker can reduce this problem

  • Floats should be placed in the water ahead of the start line to allow them to settle prior to recording, and avoid giving the floats extra momentum

  • The float should lie low in the water to ensure that it is not influenced by the wind

  • The measuring should be undertaken in an area where there are no swimmers or paddlers for safety reasons and to ensure the reliability of results

  • Any anomalies should be recorded, for example obstructions which may affect the movement of the float

  • Weather and sea conditions can have a dramatic affect on observations

Using data within an investigation

  • Data would not be used in isolation, but in conjunction with other data collected as supporting evidence

  • Most commonly used when comparing managed and unmanaged stretches of coastline, particularly the impact of management techniques on transport processes within the sediment cell

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