16' 



Water surface 



Rubber tubing 



125-ml. test tube 

 Silt 



Figure 2.--Settling funnel for collecting silt fraction in 

 bottom materials. 



Two men could sort a sample and measure 

 the volume of solids retained on each sieve 

 in about 10 minutes. 



The volume of individual samples collected 

 with the bottom sampler varied somewhat 

 from point to point but was generally within 

 10 percent of the mean. Variation in sample 

 volumes was caused by variation in porosity 

 and core depth. All sample fractions are 

 expressed as a percentage of the sample. 



Water surface 



Graduate for water 

 disploced by the 

 sieve content 



ripod legs 



Figure 3.--Device for measuring the volume of water 

 displaced by solids retained by sieves. 



PERMEABILITY AND ITS 

 RELATION TO COMPOSITION 



The permeability of spawning bed materials 

 depends on the density and viscosity of the 

 water, the porosity of the streambed, and the 

 size, shape, and arrangement of solids. There 

 is a direct relationship between permeability 

 and porosity (Franzini, 1951) and between 

 permeability and average particle size in 

 mixtures of nonuniform sizes (Krochin, 1955; 

 Childs, Collis-George, and Holmes, 1957). 

 A decrease of temperature and porosity and an 

 alteration of particle shape from spherical to 

 angular produce marked reductions in per- 

 meability of sands (Fair and Hatch, 1933), 



A standpipe for measuring permeability of 

 salmon spawning beds has been tested and 

 calibrated (Pollard, 1955; Terhune, 1958). 

 Wickett (1958) used this permeability stand- 

 pipe to measure permeability of spawning 

 beds in British Columbia streams where 

 total fresh-water survival had been measured 

 over a number of years. Wickett observed a 

 relationship between average permeability of 

 the beds and survival of salmon (fig. 4). 



