20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I47 



to place, back and forth, stopped and flowed on, as they deposited 

 their load of sandy silt and thus annually freshened areas for cultiva- 

 tion. This silting-up process was a slow one since floodwaters drop 

 only part of their burden in passing and are lightly turned aside by 

 a tuft of grass, a clump of greasewood, or a temporary barrier of 

 wind-borne sand. 



Some of that sandy silt was laid down so uniformly by gently flow- 

 ing floods as to leave floor-smooth surfaces varying in width from a 

 few feet to several hundred. Where W. H. Jackson in 1877 noted the 

 foundations of small P. Ill ruin "5 or 6 feet below the general level 

 of the valley" (Jackson, 1878, p. 443), bedded silt previously de- 

 posited extends out on either side, northward to surround Pueblo del 

 Arroyo and southward across the width of the canyon (Bryan, 1954, 

 pi. 6, upper). We came upon similar layers beneath the floors of 

 Pueblo Bonito and farther east, under the abandoned foundations of 

 a proposed Late Bonitian addition. 



In their normal course, wandering floodwaters may erode channels 

 of greater or less permanence. One such, close under the south walls 

 of Pueblo Bonito, had persisted year after year despite determined 

 efforts to dam it with village debris. It had attained a depth of 10 

 feet and its course had been turned repeatedly toward mid-valley 

 before the Bonitians won the struggle. It was a forerunner of Chaco 

 Canyon's destructive 12th-century arroyo which became Kirk 

 Bryan's primary interest in 1924 and 1925. 



Bryan first came upon this prehistoric arroyo near the southeast 

 corner of Pueblo del Arroyo where Jackson in 1877 had discovered an 

 earlier exposure 14 feet deep (Bryan, 1954, p. 32). From that 

 point of discovery Bryan traced the ancient channel up and down 

 canyon for several miles. Because sand and silt had gradually filled it 

 to overflowing and continued thereafter to accumulate until its banks 

 were buried under an additional 4 or 5 feet of alluvium, Bryan soon 

 came to refer to that prehistoric arroyo as "the buried channel." And 

 because potsherds found on the bottom of it could be correlated with 

 the final decades of Pueblo Bonito, he often employed a second 

 descriptive term, "the post-Bonito channel" (Bryan, 1925, 1926, 1941, 

 1954). 



In his published papers, and especially that of 1954, Bryan reviews 

 the history of this buried watercourse and discusses its probable 

 influence upon the occupants of Pueblo Bonito. Where Douglass 

 blames the builders for decimating the ancient Chaco forests and 

 thus hastening arroyo formation, Bryan blames the arroyo. It was his 



] 



