I believe that drone aerial photogrammetry is the most effective technique for studying coastal erosion and coastal dynamics.
And the main product to do this is the orthophoto.
Where erosion progeresses vegetation and other elements “hostile” to photogrammetry isn’t in place.
Or, at least, there’s a few.
And due to that it works well!
A photogrammetric survey made with a drone allows you to cover large areas of the coast in a short time.
And, furthermore, it allows you to repeat it in time in order to get useful data for coastal studies.
Changing of the shore line is a phenomenon which is studied and measured both on a short or long time-basis, according to the features of a beach.
Long and “thick” shores can be detected once a year.
Smaller beaches may need closer control, even after each significant storm.
By comparing the results of the surveys made in different periods of time (appropriately geo-referenced) you can understand the coastal dynamics, find the areas in regression, those in progress and plan works.