348 LOGGING 



Oxbows or curves in small streams may be remedied by making 

 a cut-off or channel connecting the two nearest points, but this 

 is too costly where bends are numerous. 



(3) There must be a sufficiently large drainage basin above 

 that part of the stream used to ensure an adequate supply of 

 flood water. Coupled with this there must be storage reservoirs 

 for holding water in reserve for flooding the stream. In the 

 North the snow on the watershed may melt and a large part of 

 it run down the streams before the drive begins. Storage basins 

 are necessary to conserve this water. 



Lakes form an admirable reservoir and when available are 

 employed for this purpose. Surplus water is caught and held 

 in them by placing dams across their mouths and when several 

 lakes are tributary to one stream driving may proceed long 

 after the natural spring freshets are over. 



Sites for dams should have a narrow channel, high banks and 

 a solid bottom for their foundation. In order to store the 

 greatest amount of water they should be built at the foot of a 

 lake, at the end of a long stretch of dead water, or in such a 

 place that the maximum amount of water can be stored with 

 a minimum of dam height. 



Storage reservoirs should be large enough to permit log driv- 

 ing for a minimum of five or six hours daily and the drainage 

 area should furnish enough water to again fill the storage basin 

 before the driving period on the following day. 



The required watershed area and the capacity of the storage 

 basins for a given stream are dependent on : 



(a) The amount of moisture precipitation on the watershed, 

 especially during the fall and winter months, and also the rapidity 

 with which it is made available in the spring. Drives are gen- 

 eially dependent on flood waters and a rapid run-off is desirable 

 because the storage basins will then be refilled in the minimum 

 time after each splash. 



The determination of whether a watershed is capable of sup- 

 plying sufficient flood water for driving purposes is a matter of 

 judgment on the part of the logger. He bases his conclusions on 

 the flood marks such as flood wood and earth deposits which 



