Scheldt River

“ At each point of impinge it cuts the alluvium away. It can bear on only a small portion of that which it thus obtains; the greater part of the material is deposited on the opposite side of the stream, but a little lower down, where it makes a shallow. On these shallows water-loving plants and even certain trees, such as the willows and poplars, find a foothold. When the stream rises, the sediment settles in this tangle, and soon extends the alluvial plain from the neighbouring bank, or in rarer cases the river comes to flow on either side of an island of its own construction. ”

“ Even overnight, even in a few short hours, a stream has been known to swell from sudden rains or snow, bringing the water with a rush down steep mountain sides and carrying with it the logs that were left strewn on the slopes or near the bank. Men work with feverish haste to roll the logs into the stream. The whole is swept into the dam, the trigger is released at the right moment and the rush of water with its freight of logs sweeps through the open gate with a mighty roar, carrying its cargo for miles on down to the river. ”

“ Stream water comes from the surface of the land or out of its porous underlayers, then flows seaward through its creases and folds, affecting the land and the land's creatures along the way and being affected by them. Thus, as we have already noted in more than one way, the management of land and the management of water are closely intertwined, from the way human use of a flood plain may demand structural interference with a river's old habits, to the way erosive farming in some West Virginia valley may help to make it harder to navigate Swedish newsprint into Alexandria by ship. ”

“ From Pebbleloggitch we made our way by a long canal-like stillwater through a land wherein no man—not even an Indian, perhaps—has ever made his home, for it lies through a weird, lonely marsh—a sort of meadow which no reaper ever harvested, where none but the wild moose ever feeds.
We were nearing the edge of the unknown now. One of the guides, Del, I think, had been through this stillwater once before, a long time ago. At the end of it, he knew, lay the upper Shelburne River, which was said to flow through a sheet of water called [Pg 96] Irving Lake. ”

“ For lack of a reservoir system to withhold and control the flow of water, the river falls from flood-tide--seventy-one feet--to points so low as to seriously impede or prevent navigation. Sometimes even the smallest steamers and barges fail to pass between Pittsburgh and Cincinnati, and coal famines have not been unfrequent, resulting from difficult navigation. An equable flow of this stream is impossible. It will always be subject to these extremes. ”

“ Thus, to some degree, the deprivation of sediment will work to the harm of the protective levees.
A flood often falls rapidly in stage. During a sudden drop, the waters dump quantities of detritus along the bed. If we deny that during flood stages the sediment can be removed from the tributary streams, we must have fear for the effect of the sudden falls in river stage. Because of the resistance offered by any construction in the flooded stream, sand would tend to accumulate about such works. ”

“ When the earth's crust is thrown up in mountain folds, and between them valleys are formed, the level of rivers is sometimes lowered and the rapidity of their flow is checked. A stream which has torn down its walls at a rapid rate becomes a sluggish water-course, its current clogged with sediment, which it has no power to carry farther. When such a river begins to build and obstruct its own waters it bars its progress and may form a lake as the outlet of its tributary streams. Many ancient rivers have been utterly changed and some obliterated by general movements of the earth's crust. ”

“ An excellent example of the latter type of stream is the Platte River, which is swift and loaded with sediment in its descent from the Rocky Mountains, but, on reaching the relatively more nearly level Nebraska country, it has its current sufficiently checked to force it to deposit sediment and build up its channel along many miles of its course, and this in spite of the fact that it still maintains a considerable current. In a mountainous arid region a more or less intermittent stream at times of flood becomes heavily loaded with rock débris and rushes down the mountain side. ”

“ That dirt all goes out before you'll have another chance to hit the hay."
Bryant arose next morning at seven. The sky was overcast and the thermometer was sixteen below zero when he examined it. Across the snow he could see the north camp stirring to life, awakening in the frosty, pallid light of dawn. Stretching thither ran uneven snowy ridges, save at one place where they lay bare and brown—the banks of the canal. When the small interval still undug was moved, the ditch would be finished from river to ranch, from the Pinas down to Perro. ”

“ Probably ninety-nine per cent of it is at once absorbed and drained away beneath the porous lava-folds of the mountain to gush forth, filtered and pure, in the form of immense springs, so large, some of them, that they give birth to rivers that start on their journey beneath the sun, full-grown and perfect without any childhood. Thus the Shasta River issues from a large lake-like spring in Shasta Valley, and about two thirds of the volume of the McCloud gushes forth in a grand spring on the east side of the mountain, a few miles back from its immediate base. ”

“ From the junction of the two principal sources in the Zardeh Kuh at an altitude of about 8000 ft., the Ab i Kurang is a powerful stream, full, deep and flowing with great velocity for most of its upper course between precipices varying in height from 1000 to 3000 ft. The steepness and height of its banks make it in general useless for irrigation purposes. From its principal sources to Shushter the distance as the crow flies is only about 75 m., but the course of the river is so tortuous that it travels 250 m. ”

“ At the same time the alluvial materials, building out to sea, thus diminish the slope of the stream. In the extreme old age of the river system the mountains are eaten down so that the torrent section disappears, and the stream becomes of something like a uniform slope; the higher alluvial plains gradually waste away, until in the end the valley has no salient features. At this stage in the process, or even before it is attained, the valley is likely to be submerged beneath the sea, where it is buried beneath the deposits formed on the floor ”

“ It is not very hard to keep a raft or any floating object in the center of the current of a stream, even if left alone at times, but the number of things which present themselves from time to time to drag it out of this channel seems marvelous.
Old watermen and rafting lumbermen know that while a river is rising it is hard to keep the channel, even the driftwood created by the rise clinging to the shores of the stream. ”

“ The instant a beaver-dam is completed, it has a decided influence on the flow of the water, and especially on the quantity of sediment which the passing water carries. The sediment, instead of going down to fill the channel below, or to clog the river's mouth, fill the harbor, and do damage a thousand miles away, is accumulated in the pond behind the dam, and a level deposit is formed over the entire area of the lake. ”

“ In mountainous districts landslips sometimes occur and block the valley of a stream which then forms a lake. The water gradually rises and eventually flows over the dam and sweeps it away causing a flood, which is of great suddenness and height but decreases very quickly in height as it travels down the valley. In a case which occurred in the Himalayas in 1888 the inhabitants of the valleys, from the dam to the point where the river debouches from the hills, were compelled by Government to vacate all habitations below the probable level of the flood, and no loss of life occurred. ”

“ The rapids thus formed are also ephemeral, for as the gradient of the tributaries is lowered the main stream becomes able to handle the smaller and finer load which they discharge.
A rare class of falls is produced where the minor tributaries of a young river are not able to keep pace with their master stream in the erosion of their beds because of their smaller volume, and thus join it by plunging over the side of its gorge. But as the river approaches grade and slackens its down cutting, the tributaries sooner or later overtake it, and effacing their falls, unite with it on a level. ”

“ Every stream has its load of sediment, as the silt- and sand-filled reservoirs along the edges of the valley so effectively testify. Each sandy river bed is an aggregate of rolling grains, moving with the current, slow where it is slow and faster where the current is accelerated, but travelling always towards the sea. ”

“ If it wasn't for the trees and brush, which prevent us seeing just where every little rise is, it would be comparatively easy, but unless we know the lie of the ground, we might plan a ditch just on the wrong side of a ridge of comparatively solid earth, which would divert the entire stream. Of course, there's a pretty good fall to the river, both the Mud River and the Red Lake River, but even so, an unobserved ridge of earth a few feet high, running along for a couple of miles would throw out the value of that particular ditch and create the cause for a new drainage area. ”

“ At the bottoms of steep slopes, temporary streams build alluvial cones or fans. Along its flood-plain portion, a stream deposits more or less sediment on its flats. The part played by deposition in building a river flat has already been alluded to. A depositing stream often wanders about in an apparently aimless way across its flood plain. At the bends in its course, cutting is often taking place on the outside of a curve while deposition is going on in the inside. The valley of the Baraboo illustrates this process of cutting and building. ”

“ Because of this spreading habit of the stream, the few villages along the way are planted on the higher land at the base of the bluffs, or on an occasional sandy pocket-plateau 245 which the river, as in ages past it has worn its bed to lower levels, has left high and dry above present overflows. Some of these towns, in their fear of floods, are situated two or three miles back from the water highway; others, where the channel chances to closely hug a line of bluffs, are directly abutting the river, which is crossed at such points by either a ferry or a toll-bridge. ”

“ To pass the drift, which is always difficult and dangerous except when the stream is exceptionally low, marks on the rocks have to be consulted. The road does not run direct across the river, but makes a wide bend; it descends to the river bed from the level of the surrounding veldt by a very steep and narrow cutting. There are huge boulders in the stream, hidden in its turbid waters, which render the crossing particularly awkward for waggons. ”

“ The appropriation was secured from the state by Mr. Menocal thirty years ago; it's never been cancelled, and is good to-day. He, however, has been using the water on ranches he owns down the river. A canal from the Pinas along the mountain sides to Perro Creek would be expensive to construct, possibly prohibitive; it appears the natural line; and I suppose this deterred him. I've located a new and practical course for a ditch on the mesa, have surveyed and mapped it in detail, calculated the cost, and compiled a statement of estimates, and can build the project for sixty thousand dollars. ”

“ This is one of the most beautiful and most instructive examples of consequent drainage—that is, of streams whose direction has been determined by the inclination of the surface over which they flow—thus far discovered. Still another feature of much geographical interest is furnished by the rivers on the adjacent plain, two of which, branches of the Cheyenne River, cross the north and south extensions, respectively, of the Black Hills dome. ”

“ They are formed by the deposit of particles of soil brought down into the main river by its tributaries, or by occasional streams created by the melting of the snow, or heavy rains. A shoal is first formed, which, as it accumulates, rises gradually above the ordinary surface, while the stream itself, if it flows like the Connecticut through a soft soil, is continually deepening its bed, and leaving these newly-formed banks out of the reach of accidental floods. ”

“ This action soon changes a straight stream with an even current, to a serpentine course with currents of different velocities, as the outside of a curve has always greater speed than the inside; consequently the outer edge is eroding while the inner is depositing sediment. The Colorado River, in the lower part of its course from Yuma down, overflows its flood plain, and deposits thereon a certain amount of sediment during every high water. ”

“ The upper level, at the outlet from Lough Allen, has a fall of 20 feet in 6 miles. The lowest level, between Castleconnell and Killaloe, contains only 641 acres of lowland, rarely flooded in summer or autumn, and rarely covered by more than 11⁄2 foot of water. To preserve the land from summer and autumn floods the surface of the floods must be lowered 2 feet nearly. A permanently solid embankment, used during many years for a navigation horse tow-path, extends along one side of the river, the only openings being four culverts for side drainage. ”