determine the amount of silt and clay deposition which has occurred as 
a result of gravel removal and washing. The operation has resulted in 
the deposition of approximately 5,000 cubic yards of silt at the mouth 
of this stream. Depth of this material ranges from less than one inch 
to several feet. 
The study clearly indicates the undesirability of allowing road-building 
material to be removed from, and washed in, tributary streams which empty 
directly into important salmon streams. To date, no gravel removal 
has been allowed in streams tributary to Maybeso Creek. The problem 
warrants careful study. Studies are needed to determine comparative 
costs and suitability of quarry material for road-building purposes. 
Silt persistence, and not solely silt quantity, is the important factor 
of potential damage to spawning facilities of a stream. The quantity 
of suspended sediment in the stream, though an index to the erosion 
behavior of the watershed, is not in itself an indicator of potential 
damage. The important question is how much of the erosion material 
which enters a stream remains to silt the bottom, and how much of it is 
carried out by normal floods. Shaw and Maga (18) state that the great- 
est damage to spawning beds occurs when silt enters a stream during dry 
periods when the water velocity is insufficient to carry the sediment 
in suspension. Water velocities necessary to dislodge deposited parti- 
cles are far greater than the velocities required to carry the same 
particles in suspension. The introduction of silt into streams during 
dry periods results in a considerable amount of bottom deposition which 
may reduce the total amount of stream suitable for spawning. The 
quiet water of deep holes, and the slower stream sections, may allow 
the fine material to settle and form a layer of silt on the stream 
bottom. 
The objective of this phase of the study is to determine the degree of 
stream siltation which occurs under natural conditions, and to what 
extent, if any, it is accelerated as a result of logging on the study 
watersheds. 
The sediment content of samples taken to date has been low. The samples 
taken in Maybeso Creek, in 1955, are from a stream where logging has 
been in progress for two years. These samples show a negligible sus- 
pended sediment content of only 1 and 4 p.p.m. Om the other hand, a 
suspended sediment content of 1,520 p.p.m. was found in Half-Mile Creek 
during the process of removing and washing road-building material in 
the stream (table 14). 
An intensified program of suspended sediment sampling is planned in 
1956. Sampling of suspended sediment will be done at all water stages. 
Analysis of these samples will be made by the U. S. Geological Survey 
Laboratory, Palmer, Alaska, and will show (1) inorganic fraction, 
(2) organic fraction, and (3) total concentration. 
SG as 
