KINDS OF DUNES (CAUSES) 



171 



applies to public forests under working plans. The distinction between 

 public and private management is described on page 186. The State 

 and commtmal forests thus lie mostly in the dimes and the private forests 

 in the level Landes behind the dune region. 



Kinds of Dunes (Causes). — The maritime dunes of France are formed 

 of sand usually drifted from the ocean or occasionally from the beds of 

 rivers near the sea. The sand dries out on the beach or river bed at 

 low tide and is blown inland. The normal dune is entirely a natural 

 phenomenon, but its movement far inland is usually caused and accentu- 

 ated by the destruction of bordering forests and soil cover. Huff el ^ says: 



Fig. 15. — Protection dune at Lacanau-Oc^an in State forest of Lacanau (Gironde). 

 The sand is held in place by planting maram grass on the wind-swept dunes. 



"Two kinds of dunes are found on the shores of Gascony: (1) Recent new dunes 

 which were fixed during the last century; (2) very old (prehistoric) ones, known locally 

 by the name of mountains, which are still covered to-day with very old forests of pine, 

 live oak and cork oak. These mountains do not form (as the recent dunes do) chains 

 of ridges separated by little ravines parallel to the shore; their confused grouping tends 

 to show that they formed at a period when the shore line was not so remarkably straight, 

 as it became in recent times, imder the action of the north-south currents." 



These recent dunes * may be of three kinds: (1) High dunes; (2) flat 



2 Huffel, Vol. I, p. 152. 



* Notes sur les Dunes de Gascogne, par J. Bert, 1900, which has been largely followed 

 in tracing the history and development of the dune reclamation work. River sand in 

 the dunes probably comes down into the Bay of Biscay from the streams of the Pyre- 

 nees and is then, according to Major Berry's conclusions, thrown up on the beaches. 



