On the south side, above the Xingu, a line of low bluffs extends, in a series of gentle curves with hardly any breaks nearly to Santarem, but a considerable distance inland, bordering the flood-plain, which is many miles wide.
The valley floor of the North Platte in the foot-hills, the flood-plain of an older river, is in places 700 ft or more below the bounding tableland, and 10 to 15 m.
In the rainy season it inundates the country throughout its course to the extent of several hundred thousand square miles, covering the flood-plain, called vargem.
Much high and dry "made" land has been reclaimed from the river flood-plain.
Nearly all of this vast flood-plain lies below the level of high water in the Mississippi, and, but for the protection afforded by the levees, every considerable rise of its waters would inundate vast areas of fertile and cultivated land.
Matthew, and are shown to contain fluviatile or channel beds with water and river-living forms, and neighbouring flood-plain sediments containing remains of plains-living forms. Thus we may complete the former physiographic picture of a vast flood plain east of the Rocky Mountains, traversed by slowly meandering streams.
Below St Paul), a picturesque expansion of the river across its flood-plain, is due to the aggradation of the valley floor where the Chippewa river, coming from the north-east, brought an overload of fluvio-glacial drift.