FLOODS 297 



2. Exclusion of grazing with the same object in view of 



keeping the soil densely covered. 



3. Careful cutting of timber on steep slopes with a 



gradient exceeding 50 per cent. Single tree selec- 

 tion is the proper method of reproduction to use. 

 Clearcutting should be prohibited. 



4. Prompt reforestation of denuded areas, in order to 



reestablish forest conditions. 



Land-slides. Land-slides occur through the action of water 

 in the subsoil or on the surface on steep slopes, particularly 

 when an impermeable layer of rock or soil prevents the 

 further entrance of the water into the ground. They carry 

 down the soil and the forest leaving a bare exposed slope. 

 Injury from land-slides may be expected in mountainous 

 regions of abundant precipitation. 



The same protective measures applicable in the forest 

 against avalanches should be employed to prevent the start of 

 land-slides. 



Floods. The influence of floods within the forest is both 

 harmful and beneficial. Damage is done by destroying young 

 plants, wounding larger trees through the action of ice and 

 floating debris and gullying and carrying away the fertile soil. 

 Deposits of rich silt may be spread periodically over the 

 ground which greatly increases the productivity of the site 

 and is distinctly beneficial. 



On forest lands subject to floods species capable of with- 

 standing inundation should be grown. Pollarding which keeps 

 the young shoots above the floods is a suitable method of 

 treatment. Selection and coppice with standards under both 

 of which methods part of the stand always remains on the 

 area are better suited to the conditions than other reproduc- 

 tion methods. 



A complete forest cover assists in preventing floods, but 



