Coastlines are dynamic places. They are constantly changing. Changes take place both over space and over time. Changes over space can be observed in the shape of beaches or cliffs or the distribution of sediment along the shore.
It is important to consider how the data you collect helps your understanding of the coastal processes along your chosen section of coastline. For example changing beach profile and sediment characteristics along a beach may be the result of transportation by longshore drift.
Questions that look at temporal change are interesting, but are often less practical for the GSCE geographer, involving repeated visits to a site for data collection. Often the secondary data we choose can add the temporal element to our work.