L 
s (in cubic yards) = ; (A + 4M + A') 
Gx. 
where s = volume in cubic yards between two adjacent 
sections 
L = length of section in feet 
A and A' = the area of the segments at the two parallel ends 
M = the area of the segment midway between the ends 
Depth of Disturbance 
Extent of sediment movement by depth-class for the six cross sections 
is shown in table 12. A considerable amount of gravel movement is 
shown to take place under natural conditions each year in the inter- 
tidal zone. The greatest disturbance in both cut and fill occurred 
in the 1.2 to 5.0 inch depth-class. Only a small percentage of cut and 
fill occurred which was greater than 9.1 inches. 
Cutting exceeds filling during some years, whereas filling exceeds cut- 
ting during other years. For example: scouring greater than 1.2 inches, 
during the period 1952-1953, was 49.2 percent, whereas deposition 
accounted for only 24.9 percent of the total change. The reverse was 
true during 1953-1954 as deposition accounted for 63.7 percent and 
scouring only 13.2 percent. Deposition exceeded erosion during the 
entire period of record by approximately 4.7 percent. Fig. 19 shows 
graphically the percentage relationship between cut and fill greater 
than 1.2 inches, and undisturbed sections. 
Severity of cut was found to be correlated with flood peaks six feet and 
greater which occurred on Harris River (table 13). The highest percent 
of heavy and severe cutting occurred during the period July 1951l-July 
1952 when the only flood greater than 7.0 feet occurred (7.95 feet, 
December 10, 1951). The lowest percentage of heavy to severe cutting 
occurred during July 1952-July 1953 when no floods greater than 6.0 feet 
occurred. No correlation was found between severity of cut and floods 
less than six feet in crest, indicating that only very high precipitation 
rates result in heavy and severe scouring in the gravel at the intertidal 
zone. Cutting is probably confined to periods of low tide when the 
"reservoir action" of tides does not decrease the velocity of streamflow 
in this area. No correlation was found between floods and severity of fill. 
Volume of Gravel Moved 
A quantitative analysis was made of the material moved in a section 
below the confluence of Harris River-Indian Creek during one winter. 
Volume of material moved between stations 0 + 00 and 2 + 00 (fig. 17) 
during July 1953 and July 1954 is shown below: 
Section Cut lili 
(cu. yds.) (cu. ydss) 
Stations 0 + 00 to 
2 + 00, intertidal 
zone 61 556 
2.33) 
