Technique two: Sediment analysis

Aims

• To examine the sorting of beach material, either across the beach profile (following the sample lines used for profiling) or across the width of the beach (linking to the process of longshore drift)

• To investigate the origin of beach material through the study of sediment cells

• To compare sediment analysis at beaches in a range of locations and attempt to explain similarities and differences

• To examine the relationship between beach sediment and other factors, for example the size and slope of the beach

Equipment

• Calipers

• Roundness or angularity charts/indexes

• Recording sheet

• Quadrats (optional)

• Random number table (optional)

Methodology

Techniques for measuring are the same as for sediment analysis in river studies. Please refer to this section for more information.

However, thought should be given to the sampling technique used to ensure that a representative sample is obtained.

Quadrats can be used to select sediment for sampling. Alternatively, ten surface pebbles touching your foot can be selected at each location. There are many different methods of sampling sediment. The different methods should be analysed by the researcher and an informed decision made as to which is the most appropriate for the aims of the investigation.

Fine Sediment Analysis

Using graduated sieves sort the sediment samples into size categories (in phi or mm sizes).

Arrange the sieves into decreasing mesh diameter. Please the sediment sample into the top sieve. Then shake the sieve and sort the sediment. Estimate the percentage of the sample in each sieve.

Considerations and possible limitations

• Deciding on the sampling strategy is very important in reducing subjectivity and increasing the validity of results. A sampling method should always be adopted to avoid the temptation to select pebbles

• Sample size should be large enough to provide a representative sample of the ‘parent population', yet not too large to be unmanageable

• The sharpest point of a stone must be measured when using the Cailleux scale and judgement of this may vary from person to person creating subjectivity

• In reality, using Power's scale will reveal mostly class five/six

• Anything which may affect the results should be noted, for example recent storms or management structures which may alter the composition of beach material