172 FORESTRY IN THE LANDES 



dunes; and (3) scattered dunes. Types (1) and (2) require no fm-ther 

 elaboration. Type (3) are dunes where the sand had formed irregu- 

 lar banks or mounds on adjacent level areas. Near the ocean the western 

 slope (facing the sea) is 4 to 25 per cent and the eastern slope 7 to 75 

 per cent. Dunes are rarely more than 200 feet high, the maximum 

 height being 292 feet in the forest of Biscarrosse. See figure 15. 



Rate of Advance. — The ends of a dune usually advance more rapidly 

 than the center, but the ridges are about parallel to the beach and at 

 right angles to the wind. They are irregular and form mounds of various 

 shapes. The rate of advance inland has been estimated at from 33 to 

 164 feet per year, depending unquestionably on the wind and on the 

 local topography. The average is probably 65 to 80 feet per year. 

 There is another phenomenon connected with the dunes — the erosion 

 of the shore line by the sea. According to my field notes : 



"At La Teste, during the period 1886 to 1912, the sea has eaten away 2,231 feet of 

 shore dunes opposite the ranger house at Gaillouneys, and at the ranger station of La 

 Sallie 623 feet has been eroded between 1886 and 1912 (86 and 24 feet per year)." 



It appears reasonably certain that the forest of Biscarrosse (partly 

 logged by the American E. F. in 1918) extended to the ocean in the 

 13th century. Huffel ^ finds no reference to moving sand prior to 1580 

 when Montaigne wrote: "Along the ocean in Medoc my brother, le 

 sieur d'Arzac, saw his land covered with sand that the sea vomited over 

 it . . . the inhabitants say that for some time . . . they have 

 lost four leagues of land." ^ A "lieve" of land was about 4.4 kilometers 

 or 2.7 miles. If this is correct it might be argued that the destructive 

 action of moving sand in France dates from about the year 1200 ij the 

 land was covered for 4 leagues inland (17.7 kilometers or 11 miles) at 

 the rate of 50 meters (164 feet) a year. But this is only conjecture. 



Local Conditions. — There are fresh water ponds between the dunes 

 from the Gironde to the Adour. Only one of these (Arcachon) is con- 

 nected with the sea so as to form a bay. The average elevation of these 

 ponds varies from 39 to 59 feet (Hourtin and Lacanau) and from 6 to 19 

 feet (Soustons). These ponds are typical of the dune region and are 

 responsible to a large extent for the unhealthy chmate of the region 

 prior to the systematic drainage undertaken by the State. The water 



^ Huffel, Vol. I, p. 153. 



6 That the area from Biscarrosse north to the Etang of Cazeau has been forested 

 for a long period is evidenced by ancient vested rights which permit residents of the 

 community to cut trees for fuel and construction. It was originally one estate, but has 

 since been divided through heirs into a multitude of holdings. The owners can take 

 the resin but have no right to cut the trees. The portion logged by the A. E. F. was 

 on the newer dunes planted by the French Government, and possibly a little farther 

 south than the old forest. 



