‘The volume determination shows clearly the unstable nature of the 
intertidal zone in terms of cubic yards of material moved during a 
typical winter period. Five-hundred and fifty-six cubic yards of 
material were moved in a 200-foot section between July 1953 and July 
1954. An examination of nine cross sections uniformly spaced over the 
study area shows that deposition which occurred in the reach between 
stations 0 + 00 and 2 + 00 was typical of the other cross sections also. 
On this basis, a total net volume of approximately 4,100 cubic yards of 
material was moved over the 1,375 lineal feet of stream included in the 
study. 
The apparent high sensitivity of the Harris River-Indian Creek inter- 
tidal zone to the actions of scouring and deposition make it an excel- 
lent area in which to study this phase of the investigation. The cross 
sections in this area will be remeasured yearly to determine whether a 
significant change occurs following logging on the Harris River water- 
shed. 
SEDIMENTATION 
Erosion material alters the environment of fish in a number of different 
ways and is generally recognized as harmful to fish population. One of 
the most important effects is the blanketing of spawning beds with heavy 
silt which may cause mortality to the buried eggs and fry by retarding 
the free circulation of dissolved oxygen to them. Other changes include: 
(1) creation of unfavorable stream bottom conditions by the retention 
of organic material and other substances, (2) alteration of temperature- 
change rates, and (3) screening out light. Silt has been found to limit 
the food supply (19). 
Several studies have been made which offer rather conclusive evidence 
that heavy stream siltation may cause severe mortality to salmon eggs 
and larvae. Shaw and Maga (18) conducted a controlled hatchery experi- 
ment with fertilized silver salmon eggs. They found that during incuba- 
tion, application of silt-laden20/ water for short periods to the gravel 
which contained the fertilized eggs reduced the yield of fry from an 
average of 16.2 percent for the unsilted control, to 1.16 percent for 
the silted gravel beds. They also found that size and vigor of surviving 
fry may be reduced as a result of siltation. Shapovalov (17), ina 
controlled experiment with steelhead trout (Salmo gairdnerii), concludes 
that silting may result in high mortality to eggs buried in the gravel. 
Smith (19) reports that placer mining silt, when fairly heavy, will 
smother salmon and trout eggs. 
Heavily silted streams do not stop the upstream migration of mature 
salmon. Salmon spawn in glacial streams which carry large quantities 
of suspended material. The available literature provides good evidence, 
however, that the most successful spawning does not occur in the heavily 
20/ Mine tailings of unpolluted soil and gravel. 
oy Me 
