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Yearbook^ of Agriculture 1949 



indicating the source of the storm run- 

 off and sediment, they point to the 

 areas that need better management. 



The next requirement for effective 

 watershed restoration is the selection 

 of the best remedial measures. These 

 fall into several categories, depending 

 upon the degree of deterioration and 

 the prospects for recovery. 



The first of these are measures that 

 will aid in the natural establishment 

 and growth of local plants. Protection 

 from fire is important. Regulated graz- 

 ing is necessary. In many sections fenc- 

 ing out all livestock is imperative. Seed 

 trees must be left when the timber is 

 harvested. In some cases all such uses 

 must be curtailed or prohibited. These 

 measures are applicable on areas where 

 there has been but slight deterioration 

 and where it is reasonable to expect 

 rapid improvement. Chief indicators 

 of successful natural revegetation pos- 

 sibilities are an abundance of seed 

 plants and a fertile soil. 



On certain areas that have been 

 overused or damaged by fire, plants 

 will not come in of their own accord, 

 because seed source is inadequate. 

 Methods of planting and seeding will 

 differ greatly for the different regions. 

 Planted and seeded areas must be 

 given intensified fire protection and at 

 least temporary protection from graz- 

 ing and trampling until the new vege- 

 tation becomes well established. 



Mechanical controls such as contour 

 trenches, water spreaders, gully plugs, 

 water drops, retaining walls, impound- 

 ing dams, and debris basins constitute 

 a third category of watershed-restora- 

 tion measures. They are essential where 

 erosion is severe and active. Mechani- 

 cal measures, in nearly all instances, 

 should be considered as methods of site 

 preparation so as to expedite vegeta- 

 tion establishment. 



It is of utmost importance that the 

 need for mechanical controls be recog- 

 nized. A too-optimistic judgment as to 

 the probable success of achieving 

 effective restoration by natural and 

 artificial revegetation will only lead to 

 failure and a more difficult and costly 



job at some future date. It is far better 

 to overdo the restoration work than to 

 risk failure by underestimating needs. 



The preservation of existing values 

 on a watershed is obviously a sounder 

 and cheaper course than restoration of 

 any kind. The primary objective of 

 maintenance is to preserve the water- 

 controlling functions of the land. This 

 means keeping storm-flow discharges 

 and sediment loads to a minimum. 

 Such an aim since soil stability is the 

 key to maintaining normal hydrologic 

 behavior can only be achieved when 

 the plant cover and soil mantle are in 

 condition to withstand damage from 

 occasional unusually heavy storms. 

 That is to say, a safety margin is neces- 

 sary. In countless cases it is the "usual" 

 storm that does the damage. 



A high degree of fire control is the 

 first requirement for maintaining sat- 

 isfactory watershed conditions. The 

 purpose of fire control in watershed 

 management is to prevent a reduction 

 in the density of the plant cover and 

 litter and in the organic-matter content 

 of the soil. Fires that bare the ground 

 and lessen the water-holding capacity 

 of the mantle almost invariably result 

 in accelerated erosion and increased 

 storm-flow discharges, even on the sites 

 where vegetation grows quickly. 



Fire-control standards vary for each 

 drainage basin and for parts of drain- 

 age basins having different runoff and 

 erosion potentials. Steep watersheds 

 that are subject to rains of great 

 volume or high intensity obviously re- 

 quire more protection from fire than 

 areas on which there is a lesser risk of 

 accelerated erosion and flood runoff. 



Fire-control plans must give ade- 

 quate consideration to the downstream 

 values. The presence of reservoirs, har- 

 bors, canals, factories, farms, com- 

 munities, and other developments so 

 located downstream as to be suscep- 

 tible of flood and sedimentation dam- 

 age may require a higher degree of fire 

 control than is needed for the protec- 

 tion of the timber, forage, or other 

 resources on the watershed lands. In 

 some places the downstream values 



