RIVER ACTION PHENOMENA 489 



floodplain. This was strongly brought out by an investigation of the great flood 

 of the Missouri river in 1881.* 

 The main facts of the report are given as follows: 



" From Sioux City to a point below Glasgow, Missouri " [that is, for GOO miles], " the valley was 

 submerged essentially from bluff to bluff. Between Sioux City and Omaha, between Platsmouth 

 and White Cloud, and between Kansas City and Glasgow, where the valley is much above the 

 average width, the overflow was not very deep, but much of the water flowed off through sloughs 

 and low portions of the valley and did not pass the gauges at all. Near Omaha, from Saint Joseph 

 to Kansas City, and from Glasgow down, the valley is narrow. In the two first mentioned portions 

 the overflow was deep, and the bed proper was disregarded, the river flowing down the center of 

 the valley. Near Glasgow the same was true to a great extent, but between that point and Cedar 

 City the river got between its banks, and from there down there was no overflow of any consequence 

 And no diversion of the water from the bed proper. The latter was quite generally silted up — at 

 least we can infer so from the deposits— from G to 12 feet in depth, which were afterwards measured 

 on islands and bars which were sheltered from the fierce currents which set up when the river 

 returned Mathin its banks. Deposits on the bottom lands were enormous in quantity and extent, 

 the immediate banks being raised for long distances from 4 to 6 feet. This afforded a very inter- 

 esting exemplification of the manner in which the banks of silt-bearing streams are raised above 

 the general level of the country. From Omaha, Saint Joseph, Kansas City, and Glasgow reports 

 were received that after the river got out of its banks the rate of rise increased, while the current 

 was so materially slackened in the course of a few hours that skiffs could row about with ease, 

 although before the river left its banks and after it returned to them the current was so strong 

 that even steamboats were unable to stem it. 



" The greatest rises heretofore observed were about 7 feet lower at Sioux City than the one under 

 consideration. Their crests took from 6 to 7 days to reach Saint Charles, while this one took 

 12 days." [Moreover, this retardation was mainly in the wide portions of the valley.] " Now it is, 

 we think, obvious that these extraordinary results can only be explained by the fact that the river 

 was out of its banks. It was practically transferred from its normal section to one of small depth 

 but miles in width. The slope was about double, but this was not enough to offset the immense 

 increase of frictional resistance. Consequently the freedom of flow was so greatly checked that 

 the water in the rear piled up on that in front and produced the abnormal rise. 



"Any fill which took plac« in the bed proper during the overflow was pretty much scoured out 

 on the falling stage, after the river got within its banks again. From all points it was reported 

 that during this period the force and velocity of the current were extraordinary. Bars which had 

 been permanent fixtures for years were removed, and a general deepening was noted on all 

 sounded sections ; but on islands and bars which were sheltered from this great scour the depth 

 of the deposits gives sufficient evidence of the extent to which fill took place during the overflow. 

 It was thought that the effect of the flood would be to leave permanent deposits which would affect 

 the low-water plane, but such does not seem to have been the case." f 



This possibility of a river putting on lacustrine conditions while its slope is 

 much increased is not only surprising but has several important bearings. 



1. It explains the common loam or silt capping extensively bottom lands and 

 terraces. To be sure, ordinary overflows tend in the same direction, but they are 

 evidently incompetent to produce the deep loam uniformly covering all such re- 

 gions. This loam is found not only deeply covering the bottom lands of the Mis- 

 souri, but also the high terraces of the Glacial epoch. Upon the latter it is found 

 frequently more than a dozen feet in depth and sometimes reaches a depth of 30 

 feet. The latter depths are found not far below the mouth of the Cheyenne river, 

 and Doctor Hayden in his report seems to have classified them with his "cal- 

 careous marl" or "loess," which he says extends along the Missouri to that point. 

 The low-level loess at Saint Joseph, Kansas City, and Glasgow, Missouri, may be 



* Report of the Mississippi River Commission, 1881, p. 13G. 

 t Missouri Geological Survey Report, vol. x, p. 207. 



