| OCR Text |
Show 3194 Dent- D 1220 and rivers that carry no sand, or very little sand, do not behave in this manner. This crossing bar may be at the end of the freshet, be considerably above the low- water surface of the water. As the freshet plays out and the river begins to fall, a time comes when the river ceases to build the bar higher, and on the contrary, begins to excavate a trend through that bar, which will eventually become the low water channel. The amount to excavation may be very considerable. I was bars along the Colorado river where it is quite certain that the excavation reached four or five feet. In the case of the Arkansas river, I have some in contact with caves where it probably reached twelve or fifteen feet. In the Mississippi, for a few miles below St. Louis, which I have inspected, although I have never been officially in charge of it, they consider that a bar which during the freshet stage does not build higher than the low water surface will cause no worry during the subsequent low water season. In other words, a river will excavate at least nine feet through that bar. In general terms, where the river is curving to the left, the deep water will be in the concave bend, close to the bank. For the trip on the Colorado river we adopted the |
