180 FORESTRY IN THE LANDES 



works by a live growth. At the same time they try to replace the former profile out- 

 lined by the caprice of the waves by a suitable artificial beach with a grade as low as 

 5 or 6 per cent, so that the wave can roll in, losing its power of erosion. Moreover, 

 each point demands a special solution. ... In fact the final dune profile is not yet 

 discovered; perhaps it will never be." 



At Lacanau they began the artificial slope of the protective dune at 

 33 feet from high tide and extended it 148 feet to where the palisade 

 originally stood. The protective dune was 52 feet high and 13 feet wide 

 (across the top) with sand barriers at each side of the top. The dune 

 then sloped gradually to a bench 164 feet farther back; perhaps about 

 65 feet farther on the lowest point was reached and the sand rose again 

 to another dune where the protective pine zone began. 



At Lacanau there were four kinds of barriers against sand erosion: 

 (1) To prevent the erosion of the tops of barrier dunes upright stakes 

 were placed 1.6 feet apart, 1.3 feet in height, with interwoven branches 

 and genista to prevent the sand from sifting through. Here the 

 ordinary palisades had been abandoned because the natural method 

 just described is considered cheaper to maintain when once the protective 

 dune is raised to the proper height by use of the palisade method. Here 

 the artificial dunes were 52 feet in height. (2) To protect the rear of the 

 protective dune rows of genista 2.3 feet high were sunk 1.1 to 1.3 feet in 

 the soil. This resulted in keeping the rear of the protective dune to the 

 proper height. (3) To hold the sand branches were laid on the sand to 

 prevent wind erosion. (4) To hold and build up areas where the sand 

 had been excavated by the wind near the ocean clumps of genista 1.6 

 feet in circumference were planted in quincunx. The French specifica- 

 tions for the "Fixation and Maintenance of Dunes" is given on page 429 

 of the Appendix. This gives a very minute and accurate account of the 

 methods now in use. According to Lafond : ^* 



"The littoral dune is the best defense in the dune region. If it is abandoned or if 

 its maintenance is not kept up, new natural dunes invariably form and, blown by the 

 wind, cover successively not only the forests created at great expense but afterwards 

 additional country." 



North of Bordeaux the protective dune seems to have assumed special 

 importance. Parallel to the ocean and at a distance of about 656 feet 

 from high tide a plank'' palisade, formed of planks 8 inches wide and 

 spaced 1.2 inches is sunk in the sand. As soon as the sand accumulates, 

 as in other dune regions, the palisade is raised about 31 inches. After 

 the dune has once been formed it is of course planted to maram grass. 



" Fixation des Dunes, par M. A. Lafond, Paris, Imprimerie Nationaie, 1900. 



" Frequently ordinary wattle work made of sticks 6.5 feet long and 2.5 inches in 

 diameter sunk 1.6 feet in the sand and 1.6 feet apart is used. These pieces are then 

 woven with branches and shrubs to a point 1.6 feet above the sand level. 



