Geology topics

Luna Bergere Leopold

Publications and source records attributed to Luna Bergere Leopold.

64 records · Page 4Linked to original sources

USGS1955

Flood control problems

Throughout the world, alluvial soils are among the most fertile and easiest cultivated. Alluvial valleys are routes for transportation either by water or by road and railroad. Rivers are sources of water, a necessity of life. But these river valleys and alluvial deposits, which have so many desirable characteristics and which have increased so greatly in population, are periodically occupied by the river in performing its task of removing the excess of precipitation from the land area and carrying away the products of erosion. How a river behaves and how the river flood plain appears depend on the relationships between water and sediment combined with the existing topography. Thus rivers and their alluvial deposits provide an endless variety of forms which are shaped, to a large extent, by the river flow during periods of rapid removal of debris and of excessive rainfall. The mechanics of river formation are such, however, that the highest discharges are not contained within a limited channel. How much water a channel will carry depends upon the frequency of occurrence of a flow. Low flows, which occur very frequently, are not important in channel formation. Neither are the infrequent discharges of very great magnitude which, although powerful, do not occur often enough to shape the channel. Channel characteristics, are dependent on those discharges of moderate size which combine power with frequency of occurrence to modify the channel from. In the highest discharges of a stream, water rises above the confines of its banks and flows over the flood plain. It must be considered, therefore, that floods are natural phenomena which are characteristic of all rivers. They perform a vital function in the maintenance of river forms and out of bank flow may be expected with a reasonable degree of regularity.

Journal of Soil and Water Conservation in India↗

USGS1954

Studies of river morphology

A number of generalizations concerning the behavior and natural characteristics of river channels have been developed by the U.S. Geological Survey in several recently completed studies of river morphology. Measurements of parameters such as the discharge, suspended load, bed material, velocity of flow, channel slope, and channel shape indicate that many river channels are characterized by an orderly, progressive change of these variables from their headwaters to their mouths. The interaction of the variables and the establishment of a stable channel suggest that the morphology of the stream is controlled by a kind of equilibrium.

Science↗

USGS1954

The flood control controversy: Big dams, little dams, and land management

The purpose of this book is to investigate the facts regarding flood control, a subject that has given rise to extreme controversy in the United States in recent years. The question of flood control is obviously a vital one not only to the United States but to many other countries. It is hoped that this book may lead to a far clearer understanding of the facts involved and so may prove a truly important influence in reconciling existing differences of opinion. Most of the material presented here has not previously been available to the general reader nor has it been easily accessible to professional people. Much of it, in fact, has been gathered by the authors from unpublished reports of government agencies and from discussions with technicians in the field. Part of the material, on the other hand, such as the sections on flood plain formation and the hydrologic effect of small dams, stems from original research by the authors.

Book↗

USGS1953

Downstream change of velocity in rivers

Because river slope generally decreases in a downstream direction, it is generally supposed that velocity of flow also decreases downstream. Analysis of some of the large number of velocity measurements made at stream-gaging stations demonstrates that mean velocity generally tends to increase downstream. Although there are many reaches in nearly all rivers where mean velocity decreases downstream, the general tendency for conservation or for downstream increase was found in all data studied. Computations of bed velocity indicate that this parameter also tends to increase downstream. Near the streambed, shear in the vertical profile of velocity (rate of decrease of velocity with depth) tends to decrease downstream. This down-valley decrease of shear implies decreasing competence downstream.

American Journal of Science↗

USGS1953

The hydraulic geometry of stream channels and some physiographic implications

Some hydraulic characteristics of stream channels - depth, width, velocity, and suspended load - are measured quantitatively and vary with discharge as simple power functions at a given river cross section. Similar variations in relation to discharge exist among the cross sections along the length of a river under the condition that discharge at all points is equal in frequency of occurrence. The functions derived for a given cross section and among various cross sections along the river differ only in numerical values of coefficients and exponents.

Professional Paper↗

USGS1953

Relation of suspended-sediment concentration to channel scour and fill

It is known that during the passage of a flood the channel of an alluvial stream scours and fills with considerable rapidity. Though such changes may be random, it seems more likely that there is a definite pattern of channel change directly related both to discharge and to the sediment load provided to the river by the drainage basin. In a study by the authors [1] an analysis was made of concurrent values of suspended sediment load and width, mean depth, mean velocity, and discharge at a number of gaging stations. From the data analyzed it appeared that fairly definite relations exist between these variables.

Conference Paper↗

USGS1953

The use of soils and paleosols for interpreting geomorphic and climatic history of arid regions

The study of modern surface soils, and ancient weathering zones, which occur either buried or as surface relicts, has contributed materially to understanding the complex events of the glacial and post-glacial period both in glaciated areas and in regions not influenced by glaciation. Most work of this kind in the United States has been done by geologists. Numerous Pleistocene geologists have noted weathered zones between sheets of glacial drift or loess in the middle western United States. These include Condra, et al 5 ; Frye 7 ; Frye and Leonard 8 ; Kay and Pearce 13 ; Leighton and MacClintock 15 ; Leverett 16 , 17 , 18 ; Lugn 19 ; Peltier 23 ; Schultz and Stout 26 ; Schultz, et al 27 ; and Simonson 28 . Kay and Pearce 13 interpreted the weathered zones between sheets of glacial drift as profiles of ancient soils which they referred to as gumbotil. Hseung, Marshall and Krusekopf 10 have recently questioned the pedogenic character of gumbotil, but have failed to offer a satisfactory alternative explanation. Thorp, and coworkers 30 , in a general review of buried soils, apparently consider gumbotil a product of ancient soil-forming processes.

Research Council of Israel Special Publication↗

USGS1951

Vegetation of Southwestern watersheds in the nineteenth century

The recollections of many old-timers who tell of grass “stirrup high” have given rise to the idea that vegetation in the Southwest was uniformly better in the middle of the last century than it is at present. The change is usually attributed to overgrazing, which timed if it did not cause extensive gullying of the alluvial valleys, I lowering the water table and decreasing the availability of water for plant use. This idea of an originally verdant vegetation, deteriorated as a result of man’s activities, has led to overoptimism concerning the possible results of reduced grazing. Obviously, any decrease in grazing pressure is a step in the right direction, but it is no exaggeration to say that recovery fo vegetation density on depleted ranges, even after protection for years, has been spotty and, in many places, disappointing. We may have allowed ourselves to be deluded by hopes of ‘restoring’ over large areas a level of vegetation density that was originally attained only in selected localities. This conclusion is supported by the published diaries and field notes of members of early American exploring parties. They show that in certain places, particularly in south-central Arizona where grass is now meager, the alluvial valleys formerly supported large expanses of grassland. However, there were also many areas, even alluvial valleys, where grass was so poor that forage for a string of horses could hardly be obtained. Other areas, such as the Rio Puerco Valley, supported good grass in some places but only scattered shrubs, furnishing poor forage, in others, though until well past the middle of the nineteenth century extensive grazing had been prevented by frequent raids of hostile Indians.

Southwest↗

USGS1951

Alluvial fills near Gallup, New Mexico

Valleys near Gallup, N. Mex., similar to many in the Southwest, were filled in Recent time with alluvium. This material is now being eroded by systems of gullies, and the walls of these gullies provide exposures by which the history of the deposition of the alluvium can be traced. Alluvial fills near Gallup have been eroded at least twice previously within Recent time. The middle fill of the three that are recognizable contains potsherds of Pueblo II age, indicating that deposition was occurring as late as A. D. 1200. The chronology of alluviation and degradation for valleys in the Gallup area appears to agree with that for other valleys in the Southwest which have been studied.

New Mexico↗

USGS1951

Conservation: Where we stand: Review of Water, land, and people

A distinguished conservationist, just returned from more than a year in those Pacific islands held in trust by the United States, reports that representatives of the government there are nearly completely concerned with the maintenance of an administrative organization. Actual advances in matters of land use, of maintaining the material and mental welfare of the native population, and the preservation of the most interesting remnants of untouched habitat, are just never made. Any such oversimplification is, of course, subject to error in detail, but it nevertheless stands as a touchstone to where we stand in conservation. In much more guarded phrases, and with considerable supporting data, Bernard Frank and Anthony Netboy say much the same thing about governmental conservation in the United States in their recently published Water, Land, and People .

The Living Wilderness↗