470 JOHN LYON RICH 



The Intrenched Meander Valley^ is one whose stream, having 

 inherited a meandering course from a previous erosion cycle, has 

 sunk itself into the rock with little modification of its original course. 



The In-grown Meander Valley is one whose stream, which may or 

 may not have inherited a meandering course from a previous cycle, 

 has developed such a course or expanded its inherited one as it cut 

 down. Thus, as the stream sunk its channel lower and lower into 

 the bed-rock, the meanders were continually growing or expanding. 

 The term "in-grown" has been chosen to express this idea. 



Three valleys illustrating the above types have been selected 

 from the United States Topographic Atlas. A brief description of 

 each should bring out the most essential characteristics of its type : 



I . Typical of the first group, the open valley, is that of the Kana- 

 wha River as depicted on the Charleston (W.Va.) special sheet; 

 U.S. Geol. Survey (see Fig. i). The valley of Elk River, entering 

 the Kanawha at Charleston, also illustrates this type as developed 

 by a smaller stream. 



The "thalweg," or immediate trough of the Kanawha River, is 

 sunk some six or seven hundred feet below the general level of the 

 neighboring upland, which it traverses in broad, open curves. The 

 valley bottom is fiat and about two-thirds of a mile wide, or about 

 six times as wide as the stream. The sides are steep and trimmed 

 to remarkable regularity — being, in fact, practically parallel. There 

 is a slight tendency to greater steepness of the concave bank on the 

 sharper bends. In this open, fiat-bottomed valley the stream 

 swings in broad, free curves, now hugging one bank, now the other. 

 A space of something like six miles intervenes between successive 

 points of impingement against the same bank. The curves of the 

 stream in its swinging do not everywhere correspond with those of 

 the valley trough. 



The flat bottom, so conspicuous in the valley of the Kanawha, 

 is not considered an essential feature of the open valley. A non- 

 meandering valley with a V-shaped cross-section would, in the sense 



'The term "incised meander" has, apparently, been used synonymously with 

 intrenched meander in previous writings. Would it not be well to use "incised 

 meander" as a generic term covering both the above-described cases, and to restrict 

 the meaning of intrenched meander as indicated above? 



