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Show 241 which we have, they refer to the creation of a head in the water. Just for the record, will you explain what you mean by a head? A. Well, I have used the word " head" in the same way that you use it in speaking of the head of a dam-- the difference in the elevation above and below the dam; it is the difference in elevation above and below the riffle. Q. When you say a head will be created of three feet in a distance of a thousand feet, that means it will be a fall? A. I mean the profiles or surveys show that there was an actual fall of three feet in that distance of 1,000 feet. Q. Now, in the study of river flows, where, for instance, a rise of two feet is indicated on the gauge, will that necessarily produce a two- foot depth of water on riffles and sandbars? A. No, sir. Q. Well, just explain the situation with reference to that. A. Well, on account of the changes in slope of a river, and changes of width at different places, a rise of two feet at any one place did not necessarily mean that there would be a two- foot rise at any other place. Given the same hydraulic conditions, the same cross section, and the same slope at another cross section, there would probably the same two- foot rise. But if you increase your width, or change your slope, 2204 |