30 
MUSEUM BULLETIN NO. 11. 
the mile from the southern limit of the quadrangle to Trapper 
creek, and 40 feet to the mile for some distance above that point. 
The profiles of the side streams show stretches of steep grade 
followed by long flats which are in turn succeeded by steeper 
grades. Upon such stretches lakes and swamps often occur, 
while the steeper bed grades are usually in canyons. The 
smaller tributaries of the West Fork, like China and Curry 
creeks and St. John and Crystal creeks which flow into the 
Beaver, generally have steep gradients within the canyons 
through which they enter the valley of their master stream, and 
flatter grades in the upper upland troughs. Beaver creek has 
a very variable gradient and falls in a series of three steps from 
the source at Joan lake to its junction with the West Fork at 
Beaverdell. The flats or treads of these steps lie in U-shaped 
or upland valleys, the raises in canyons sunk in such valleys. 
The grade varies from 40 to 80 feet per mile in the flats and 100 
to over 200 feet per mile in the raises. 
Discordance between Valley Size and Stream Volume . 
Comparison of the stream volumes of two confluent creeks 
sometimes shows that the larger volume of water is being car- 
ried by the smaller valley. Such is the case where Trapper 
creek enters the West Fork, the valley of Trapper creek being 
about twice the size of the corresponding part of the West 
Fork and carrying less water. Another instance is seen at the 
junction of Beaver and Maloney creeks. 
An extreme case is that of Wallace draw, a broad valley 
connecting the West Fork and Beaver creek. Its highest point 
is about 40 feet over Wallace lake, which lies on the surface of 
an extensive terrace on the floor of the West Fork valley and the 
slope from this point to the Beaver is much less, while its valley 
is wider than that of the Beaver above the point where they come 
together. Nevertheless the Beaver carries a fair sized stream 
while Wallace draw is practically dry. The reasons for this 
are discussed under the heading of “Stream Piracy,” page 45. 
