Heavy accumulation of debris in critical areas may be harmful in that 
it may block the upstream migration of spawning salmon. Debris may 
change the stream course and thus set up a reaction which is felt for 
many miles downstream. The effect of debris and log jams in streams 
is not as yet settled, however. The presence of this material may be 
beneficial as well as harmful. Stream barriers are generally transient 
in nature and new channels are soon formed under or around these 
barriers. Pools created by jams provide natural hiding places for the 
salmon. During mapping and spawning surveys it was observed that 
salmon congregated in considerable numbers in places where a protecting 
‘ cover of debris existed. 
Pools and Riffles 
The difficulty of mapping pools in place, and the subjective nature of 
pool identification, prevents a quantitative determination of the status 
of pools from year to year. The mapping project demonstrated, however, 
that pools may change in shape, depth, and total number from year to 
year. Water action was observed to deepen a pool in one area, while 
another pool was being filled with sand and gravel. Debris, in the 
form of stumps and large windfalls, was observed to play an important 
part in the formation, or elimination, of pools. The obstruction may 
change the natural waterway a slight amount, and by so doing, may set 
the stage for the creation of a pool where at present a gravel bar 
exists: (fic... 15) 
The study reveals that the equilibrium of stream channels under natural 
conditions is subject to great change and that new pools are constantly 
being formed and old pools filled as a result of water action. 
Area of stream in riffles does not appear to be greatly changed from 
year to year as a result of water action. Riffles mapped during 1949 
were still present in the same general position in 1953 on all streams. 
Streambank Cutting 
Very little cutting of overhanging mud and clay banks has occurred. 
Maybeso Creek has received approximately 1300 lineal feet of bank 
cutting; Harris River 100 feet; Indian Creek 450 feet; and Old Tom 
Creek 165 feet. 
A considerably greater amount of streambank cutting occurs than is 
indicated by the above figures. The greatest proportion of streambank 
material is composed of glacial-lain deposits of sand and gravel. This 
material is easily molded and reworked by running water. It is usually 
difficult to recognize, and to map planimetrically, fresh cutting in 
sand and gravel unless the change is of large magnitude. An intensive 
cross-section study was begun at the confluence of Harris River-Indian 
Creek in 1950 to determine the extent of yearly cutting in sand and 
gravel. This study is described later. Twelve additional cross- 
section stations were established on Maybeso Creek and six on Harris 
River in 1954 and 1955. 
= 034s = 
