What kind of dunes are these ?

thats a fairly recent phenom on that spit. The "dunes" seem to have been built by longshore drift, not wind. SO these may really be hydraulic features common to spit. Yet they are being washed and truncated on the seas side. Ive seen many a sand spit grow and cover in a cove or cape.

Usually dune names and feqtures are more reserved for wind structure because hydraulic dunes always respond to the wneregy filed of thw current.

You should get some historical ir photos to be accurte but if iots a school projct. Your answer must be modified to say why these re technically NOT longitudinals.

the feature is called a barrier bech but as it grew, you can see that towrds the bottom of the picture are some kinds of crescent fetures consistent with convex or barchan dunes

Thanks for your answer. I'll give you some more data. (sorry for bad english)

Our field trip teachers always said they were dunes. They did not specify the type anyway. They also talked about these " dunes " were interfered for economic purposes.

I attached some additional images:




They talked about " stratifications " ( not really, since they are unconsolidated sediments) in the " dunes " . crossbedding present too



Here I observed an alternation between sands of lighter and darker colors

2006 year

2012 year

these are wind generated(you can see the cross bedding) So the specific type of longitudinal dune is really immaterial , since they are being transgressed from an apparently rising water level and long shore current.
Interesting cross sections, where are the dune fields?