FACTORS AND TABLES OF EQUIVALENTS USED IN FORESTRY 13 

 Table 21. — Grade percent and equivalent degree of slope 



Grade 

 (Percent) 



Slope in 

 degrees 



Grade 

 (Percent) 



Slope in 

 degrees 



Grade 

 (Percent) 



Slope in 

 degrees 



Grade 

 (Percent) 



Slope in 

 degrees 



1 



o / 



34.4 



1 8.7 



1 43.1 



2 17.4 



2 51.7 



3 26.0 



4 0.3 



4 34.4 



5 8.6 

 5 42.6 



11 



/ 



6 16.6 



6 50.6 



7 24.4 



7 58.2 



8 31.8 



9 5.4 

 9 38.9 



10 12.2 



10 45.5 



11 18. 6 



21 



/ 



11 51.6 



12 24.4 



12 57.2 



13 29.7 



14 2.2 

 16 42.0 

 19 17.4 

 21 48.1 

 24 13.7 

 26 33.9 



55 



60 



65 



70 



75 



80 



85 



90 



95 



100 



/ 



28 48.6 

 30 57.8 



33 1.4 



34 59.5 

 36 52. 2 

 38 39.6 



40 21.9 



41 59. 2 

 43 31.9 

 45 



2 



12 



13 



22 



23 



3 



4 



14 



24 



25 



5 



15 



6 



16 



30 



7 



17 



35 .. 



8 



18 



40 -. 



9 



19 



20 



45 



50 



10 







> Equivalents of customary expressions of grade are as follows: 



Grades and slopes: 1 foot per chain= 1.515 percent; 1 foot per mile=0.018u33 percent; 1 millimeter per 

 meter = 0.1 percent; 1 foot per thousand =0.1 percent; 1-percent grade =633. 6 inches per mile=52.8 feet per 

 mile = 10 millimeters per meter=10 feet per thousand feet=l foot per 1.515 chains=0.06 feet per chain. 



Table 22. — Degree of slope and equivalent grade percent 



Degree of 

 slope 



Grade 



Degree of 

 slope 



Grade 



Degree of 



slope 



Grade 



Degree of 

 slope 



Grade 



/ 



Percent 



o / 



Percent 



o , 



Percent 



/ 



Percent 



30 



0.873 



5 



8.749 



9 30 



16. 734 



18 



32. 492 



1 



1.746 



5 30 



9.629 



10 



17.633 



19 



34. 433 



1 30 



2.619 



6 



10. 510 



11 



19. 438 



20 



36. 397 



2 



3.492 



6 30 



11. 394 



12 



21. 256 



22 30 



41. 421 



2 30 



4.366 



7 



12. 278 



13 



23. 087 



25 



46. 631 



3 



5.241 



7 30 



13. 165 



14 



24. 933 



30 



57. 735 



3 30 



6.116 



8 



14. 054 



15 



26. 795 



35 



70. 021 



4 



6.993 



8 30 



14. 945 



16 



28. 675 



40 



83. 910 



4 30 



7.870 



9 



15. 838 



17 



30. 573 



45 



100.0 





Table 23.— Scale 



of velocity equivalents of the Beaufort scale of 



wind 



Beau- 



Description 



Indicators of velocity 



Velocity 



fort 

 scale 

 no. 



Meters per 

 second 



Miles per 

 hour 







Calm 



Calm air; smoke rises vertically 



Direction of wind shown by smoke drift, 



but not by wind vanes. 

 Wind felt on face; leaves rustle; ordinary 



vane moved by wind. 

 Leaves and small twigs in constant mo- 

 tion; wind extends light flag. 

 Raises dust and loose paper; small 



branches are moved. 

 Small trees in leaf sway; crested wavelets 



form on inland waters. 

 Large branches in motion; whistling 



heard in telegraph wires; umbrellas 



used with difficulty. 

 Whole trees in mo! ion; inconvenience felt 



when walking against wind. 

 Breaks twigs off trees; wind generally 



impedes progress. 

 Slight structural damage occurs to signs; 



branches broken. 

 Trees uprooted or broken; considerable 



structural damage occurs. 

 Very rarely experienced; accompanied 



by widespread damage; forests wind- 

 thrown or broken off. 



Less than 0.3 



0.3 to 1.5 



1.6 to 3.3 



3.4 to 5.4 



5.5 to 7.9 



8.0 to 10.7 



10.8 to 13.8 



13.9 to 17.1 



17.2 to 20.7 



20.8 to 24.4 



24.5 to 28.4 



28.5 to 33. 5 



33.6 or above 



Less than 1. 



1 

 2 



Light air 



1 to 3. 



4 to 7. 



3 





8 to 12. 



4 

 5 



Moderate breeze 



13 to 18. 

 19 to 24. 



6 





25 to 31. 



7 





32 to 38. 



8 



Gale 



39 to 46. 



9 





47 to 54. 



10 





55 to 63. 



11 





64 to 75. 



















