Thick as Autumnal Leaves

You would be forgiven for thinking these were dead leaves, it being autumn and all that, but in fact it's seaweed, kelp in particular, that has been torn from its seabed moorings by the recent storm  and now lies heaped along the strand line "thick as Autumnal Leaves that strow the brooks  in Vallombroso".

(I am not quoting John Milton's epic simile in order to be pretentious but because it fixed itself in my mind when we 'did' Paradise Lost Book One at school and at this time of year it invariably comes back to mind.)