River system

“ They are short-lived, for their destruction is soon accomplished by several means. As a river system advances toward maturity the deepening and extending valleys of the tributaries lower the ground-water surface and invade the undrained depressions of the region. ”

“ There is nothing more striking in geography than the perfection of the adjustment of a great river system to its valleys when the land has remained stable for a very lengthened period. Before full adjustment has been attained the river bed may be broken in places by waterfalls or interrupted by lakes; after adjustment the bed assumes a permanent outline, the slope diminishing more and more gradually, without a break in its symmetrical descent. ”

“ Stately and slow that river moves down to the bay, into which it empties its load. The rain that falls on hundreds of square miles of territory flows into the streams that feed this trunk. The little spring that is the headwater of the system is but one of many pockets in the hillsides that hold the water that soaks into the ground and give it out by slow degrees. Surface water after a rain flows quickly into the streams. It is the springs that hold back their supply and keep the rivers from running dry in hot weather. ”

“ These are the natural consequences which must follow if the land has long been worked upon by streams, and no other process has ever been suggested which is competent to produce them. We must conclude that valley systems have been formed by the river systems which drain them, aided by the work of the weather; they are not gaping fissures in the earth's crust, as early observers imagined, but are the furrows which running water has drawn upon the land. ”

“ There remains but one important point to be considered—one which has exerted a very great influence on the diversity of structure in all river systems, controlling the area of their drainage, their volume of water, their effect on human culture, and on the ethnographic character of the people dwelling on their banks. ”

“ A torrent that issues from its source in the mountains is not the river which reaches the sea. On its long journey from highland to lowland it receives now the milky waters of a glacier-fed stream, now a muddy tributary from agricultural lands, now the clear waters from a limestone plateau, while all the time its racing current bears a burden of soil torn from its own banks. Now it rests in a lake, where it lays down its weight of silt, then goes on, perhaps across an arid stretch where its water is sucked up by the thirsty air or diverted to irrigate fields of grain. ”

“ A river that spreads out into the indeterminate earthform of a marsh is an effective barrier; but one that gathers waters into a natural basin and forms a lake retains the uniting power of a navigable stream and also, by the extension of its area and elimination of its current, approaches the nature of an enclosed sea. Mountain rivers, characterized by small volume and turbulent flow, first become navigable when they check their impetuosity and gather their store of water in some lake basin. ”

“ Two or three hundred yards has been the limit of the view ahead, as the stream swerves gracefully from the slightest rise of land, and flows now east, now north, now east, now south again. So long a stretch of navigable water is not common on the Delectable River, and we make the most of it, moving leisurely, and prisoning the everchanging picture with the imperfect camera of the eyes. ”

“ If we would discover how a watercourse is formed, from the very first bog-streams up in the mountain, we must follow a multitude of tiny rills, receiving one fresh stream after another from every side, running together into burns, which grow and grow and form little rivers, till we come to the end of the wooded hillside and are suddenly face to face with the great river in the valley below. ”

“ So our rivers are doing to-day what they have always done—they are tearing down rocks, grinding and sifting the fragments, and letting them fall where the current of fresh water meets a great body of water that is still, or has currents contrary to that of the river.
Do you see a little dead fish in the water? It is on the way to become a fossil, and the mud that sifts over it, to become a layer of slate. Every seashore buries its dead in layers of sand and mud. ”

“ The soil and the deep-striking roots of the forest terminate far above you, looking like a black rim on the inclosing precipices; the bed of the river and its sky-sustaining walls are of solid rock, and, with the tremendous descent of the stream—forming for miles one continuous succession of falls and rapids—the channel is worn into curves and cavities which throw the clear waters into forms of inconceivable brilliancy and variety. ”

“ The rain continuing, and the stream rapidly rising, we halted at some farm-houses in the midst of a long rice-field. Fording the river is difficult work; the water rushing down at headlong speed, renders it necessary to exert one’s utmost strength to avoid being carried away: the pole in both hands, placed well to seaward, one foot advanced cautiously before the other, to avoid the slippery rocks and loose stones. I found that this fatigued me more than the walking. The water became much cooler as we approached the mountain, while the land is rapidly increasing in elevation. ”

“ When full they are inevitably muddy, and when empty are very empty indeed; lifeless, and mute at the best, at the worst actually dry. The river of low-country birth acquires, in short, neither{2} character nor quality worthy of consideration till as a full-grown stream it can trace a shining coil in the valley, or reflect the shadow of spire, bridge or mill, of willow or poplar. ”

“ The regulation of a river consists in straightening its channel by cutting off bends, securing its banks from erosion by floods, and, where necessary, by constructing embankments to confine the waters and prevent them from overflowing and stagnating upon the low grounds which skirt their current. ”

“ They flow between low, rounded hills, and are joined by quiet streams, that occupy the separating grooves between the hills. This is the oldest type of river. It has done its work. Rainfall and stream-flow have brought the level of the land nearly to the level of the stream. Very little more is left to be ground down and carried away. The landscape is beautiful, but it is no longer picturesque. Wind and water have smoothed away unevennesses. Trees and grass and other vegetation check erosion, and the river has little to do but to carry away the surface water that falls as rain. ”

“ Whether a river begins its life on a lake plain, as in the example just cited, or upon a coastal plain lifted from beneath the sea or on a spread of glacial drift left by the retreat of continental ice sheets, such as covers much of Canada and the northeastern parts of the United States, its infantile stage presents the same characteristic features,—a narrow and shallow valley, with undeveloped tributaries and undrained interstream areas. Ground water stands high, and, exuding in the undrained initial depressions, forms marshes and lakes. ”

“ The banks of the stream are sandstone and sand, and the channel scarcely three yards wide, with a strip of grassy thicket twenty yards in width along the stream, which is the only feed near the river, as the plain through which it runs produces nothing but scrub and banksia with a few grass-trees. ”

“ But, frequently, a very large marsh is traversed by a tortuous stream which occupies a large area, and which, although the tidal water which it contains gives it the appearance of a river, is only the outlet of an insignificant stream, which might be carried along the edge of the upland in an ordinary mill-race. ”

“ A river flowing to the sea or emptying itself into an inland lake, carries its burden of gravel, sand, and mud, and sooner or later, as the rate of flow slackens, it deposits the materials in the river-bed or on the floor of the sea or lake. ”

“ As far as the eye could reach was a prosperous plain, watered by a wide river, abundantly irrigated by canals and subterranean aqueducts, broken up by green hedges and well-cultivated fields; for the ground was rich, and the temperate climate favorable to farming. ”

“ This is the typical river of which there are infinite varieties, yet every variety would, if time were given, and the land remained unchanged in level relatively to the sea, ultimately approach to the type.Adjustment of rivers to land. Movements of the land either of subsidence or elevation, changes in the land by the action of erosion in cutting back an escarpment or cutting through a col, changes in climate by affecting the rainfall and the volume of water, all tend to throw the river valley out of harmony with the actual condition of its stream. ”

“ More to the purpose of the present moment, the government engineers have expelled the quicksands and confined the waters so that from the vagaries of running waves of sand and shallow films of water, true channels have been forced through, and the old two or three feet of available low-water depth has been increased to eight or ten feet, practically guaranteed up a thousand miles of river. ”

“ Alluding to the custom of irrigation in the eastern countries, where streams are conducted from a canal or river to different parts of the ground, and turned off or on at pleasure; the person having no more to do than by his foot to turn a sod from the side of one stream, to cause it to share its waters with the other parts to which he wishes to direct his course. ”

“ In regions of abundant rainfall every slope is abundantly supplied with streams, and therefore those streams which cut back their region of origin most rapidly will necessarily encroach upon their neighbours’ territory. They therefore tend to tap some of the tributaries of the other streams, a phenomenon which has sometimes considerable human importance, and has been extensively studied of late years under the name of river-capture. ”

“ It is because of this progressive reduction of grades with increasing age that the early stages of a river’s life are much the most turbulent of its history. The water then rushes down the steep grades in rapids, and is often at times opened out in some basin to form a lake where differences of uplift have been characteristic of neighboring sections. ”

“ The slope of the river bed diminishes until the plain compels the river to move slowly, swinging in meanders proportioned to its size, and gradually, controlled by the flattening land, ceasing to transport material, but raising its banks and silting up its bed by the dropped sediment, until, split up and shoaled, its distributaries struggle across its delta to the sea. ”

“ Winding walks of great extent, pass through close thickets and groves interspersed with lawns; and streams, diverted from the river Isar, traverse the grounds swiftly in various directions, the water of which, stained with the clay of the soil it has corroded in its descent from the upper country, is frequently of a turbid white colour. ”

“ The forest-born stream is the useful and beautiful one. It has a steady flow of clear water, and fishermen cheerfully come to its green, mossy banks. The buildings along its course are safe from floods, and are steadily served with the power of its reliable flow; its channel is free from mud and full of water; it allows the busy boats of commerce freely to come and go; in countless ways it serves the activities of man. It never causes damage, and always enriches and gladdens the valley through which it flows on to the sea. ”

“ Model the upper part of a river valley, showing the river with its tributary streams and ravines. Show the high rocky banks where the river is narrow and the low banks where the stream is wider. Determine at what place in the river a dam would be apt to be formed during the melting of the snow in the springtime, and what parts of the valley would be flooded first. Then get a clear idea of the way that the flood that is referred to in this lesson took place by modeling an underground channel that connects with the river on the one hand and with the outer world on the other. ”

“ Even richer, if that be possible, than the fauna of the river, and at any rate more diverse, is that to be found at the proper season on the shores and surface of all the lakes and larger water-pools which lie within the forest and are filled either by the spring rains or by the full floods of the river. ”

“ Any newly formed land surface, like a recently drained lake bed or part of the marginal sea bottom which has been raised into land, has a drainage system developed upon it. In the early or youthful stage of such a new land area lying well above sea level, under ordinary climatic conditions a few streams only form and these tend to follow the natural or initial slope of the land. ”

“ Torrential streams tend to excavate or to raise their beds according to the inclination, and to the character of the material they transport. No general law on this point can be laid down in relation to the middle and lower courses of rivers. The conditions which determine the question of the depression or elevation of a river-bed are too multifarious, variable, and complex, to be subjected to formulae, and they can scarcely even be enumerated. ”

“ When, in consequence of the flow of a river channel through an alluvial soil not yet REGULATED, or, in other words, which has not acquired its normal inclination, the course of the river has not become established, it is natural that its bed should rise more rapidly after its embankment. ”

“ When several such valleys run into a common one, like so many tributaries to a river, and especially when the upper reaches contain snow and the whole section is devoid of forest, the aerial river is likely to become torrential in nature along the lower reaches of the drainage channel. ”