Riffles. Area of the 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 in any study stream during the period 1949 through 1953 o 

 Maybeso Creek has approximately 1300 lineal feet of streambank cutting; 

 Indian Creek, 450 feet; Harris River 100 feet; and Old Tom Creek, 165 feet. 



A considerably greater amount of channel change and streambank cutting 

 occurs than is indicated by the above figures, however. The greatest pro- 

 portion of streambank material is sand and gravel. The glacial-lain 

 deposits of sand and gravel, over which the majority of these streams run 

 their course, are easily molded and reworked. It is usually difficult to 

 recognize, and to map planimetrically, fresh cutting in sand and gravel 

 unless the change is of large magnitude. Several cross section stations 

 were established on Maybeso Creek and Harris River, in 1954 and 1955, which 

 will permit a quantitative analysis of the magnitude of cutting in sand 

 and gravel banks. An intensive study at the confluence of Harris River and 

 Indian Creek, begun in 1950 to measure streambed contour change as a result 

 of deposition and bottom scour, also allows a quantitative analysis to be 

 made of cutting in sand and gravel. 



Intertidal zone change . The intertidal zones-' of many streams in South- 

 east Alaska are widely \ised by pink salmon ( Onchorhynch\js gorbuscha ) as 

 spawning areas. A very high percentage of the total number of pink salmon 

 using Harris River and Indian Creek have been observed to spawn in the 

 riffle area at the confluence of these two streams. Salmon eggs and fry 

 buried in the gravels in this zone are covered with salt water diiring a 

 substantial part of the incubation period. 



The intertidal zone at the confluence of Harris River-Indian Creek is com- 

 posed of alluvial deposits of sand and gravel. Intertidal sections are 

 frequently less stable than stream channels above high-tide level, and 

 streambed material is easily molded and reworked by heavy fall and winter 

 floods. The stream mapping project, mentioned earlier, showed that a con- 

 siderable amount of streambed material is shifted annually in this zone. 



The welfare of salmon eggs and fry which are in the streambed gravels is 

 directly affected by the magnitude of movement of fragmental mineral debris - 

 gravel, sand, silt, and clay - in important spawning areas. Heavy mortality 

 of eggs and fry might occur as a result of the deposition of fine material, 

 or streambed scouring which removes the protective covering of gravel. 



Another agent of distiirbance in intertidal areas is the action of winter 

 ice. Large sheets of ice are broken and moved over the spawning beds. 

 This action results in considerable grinding and scouring of streambeds. 

 Quantities of rock and sediment are deposited in the grass flats when this 

 ice is forced out of the stream channels onto the banks. 



6/ The intertidal zone is considered to be the stream sections between 

 the lower low-tide and higher high-tide level o 



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