RANGE PRESERVATION AND EROSION CONTROL. 7 
rim of the Wasatch divide, where fan-shaped drainage basins are 
characteristic. 
Practically all the torrential floods which are responsible for the 
most serious destruction of property originate near the heads of the 
watersheds, usually at high altitudes. On the Manti Forest the most 
vital part of the watershed is that lying between altitudes of about 
9,000 to 10,500 feet, within what is known as the spruce-fir type. 
HI Ml Yarrow-Meed/egrass-Cinquefoil ' 
y//\ Yarrow- Doug las Knot wood (Semi-barren) \ 
\=\ Adder's tongue-larkspur-SweetSage 
|ttt-| Currant- Gooseberry -Yarrow 
^7J\ 8/ueyrass-Whear<prass-Needlec?rass (Semi-Scabland) 
\:^ dan f Larkspur - Blue foxglo ve -Douglas Knotnood 
gg| Yellow brush- Sweet Saye-Peatine 
[03] Spruce 
^^ Slder 
* Dry rills 
Fig. 1. — Erosion areas A and B, head of Ephraim Canyon, Manti National Forest, Utah. 
It is on these elevated lands that the rainstorms are the heaviest and 
most violent, the slopes are steepest, and conditions in general most 
favorable to erosion. 
The greater part of this upper mountain region consists of large 
fan-shaped basins which drain through narrow canyons into the 
valleys below. These canyons are relatively short and have a steep 
grade. Ephraim Canyon, for example, has an average grade of about 
22 per cent, or approximately 1,160 feet to the mile. So rapid is 
