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Luna Bergere Leopold

Publications and source records attributed to Luna Bergere Leopold.

At least 55 records · Page 3Linked to original sources
USGS1963

Simple measurements of morphological changes in river channels and hillslopes

One of the principal types of observational evidence on climatic changes in the recent geologic past is in river position and elevation. It is well known that river channels, particularly those flowing through alluvium or on relatively soft bedrock, tend to develop flood plains by lateral migration of the channel. Abandoned flood plains at elevations distinctly above the present river channel are the origin of river terraces, widespread through the world but particularly noticeable in arid regions. Climatic change is one of the causes of the abandonment of flood plains and the consequent formation of river terraces. Therefore, the identification and stratigraphy of river terraces is one of the methods by which climatic changes in the recent geologic past can be studied. There are, of course, morphologic changes in river channels of a more subtle nature. Even when a channel is progressively degrading-a trend which will eventually result in the formation of a river terracethere are no obvious criteria by which the current changes in a river channel can be positively identified. For this reason simple techniques, which will aid in the direct observation of current changes in a channel’s position, can be helpful in identifying the nature of changes in progress. It is the purpose of this paper to describe some relatively simple techniques which have been found to be useful in observing morphological changes on slopes and in channels. The methods have been tested primarily in arid climates but to some extent they can also be useful even where vegetation is prominent.

Conference Paper↗
USGS1963

Some climatic indicators in the period A.D. 1200-1400 in New Mexico

Three centuries before Columbus landed in America, the alluvial valleys of the south-western United States teemed with activity. The indigenous peoples had been building for 300 years a culture centred around community life based on flood-water farming and on hunting. A large number of pueblos had developed on sites earlier occupied by pit-house people. Community organization had brought advances in the ceramic and decorative arts, and changes in these artistic activities were sufficiently rapid that accurate chronologies have become available through the work of archaeologists during the twentieth century. These chronologies were at first unrelated to absolute dates, but the excavations of the 1920s at Chaco Canyon (New Mexico) provided the materials through which absolute dates could be established. This was accomplished by matching the changes in tree-ring width backward in time from living trees through successively older samples. Trees overlapping in age provided, by unique successions of distinctive tree-ring widths, a calendar by which individual logs could be dated. Beams found in the excavations at Chaco Canyon gave the first material by which the cultural developments culminating about A.D. 1300 could be dated. As a result of the time sequence provided by the tree-ring calendar, the dates within which different pottery types were developed could be accurately established. The dates of pottery types have been checked at a sufficiently large number of sites throughout the south-western United States that absolute dating of a large number of distinctive patterns can be considered unassailable. The sequence of tree-ring widths gives some climatic indications of great interest both to archaeologists and to climatologists. A relatively large number of logs spanning the period from A.D. 1200 to 1300 and, in particular, the years between 1276 and 1299, indicate that this period was generally characterized by smaller tree-ring widths than in the centuries immediately before and after. As a first approximation, the hundred years of narrow tree-ring widths were interpreted as a time of relative aridity, and have been referred to as the “Pueblo Drought”. More recent studies of tree-ring widths using sophisticated statistical techniques have thrown some doubts on any direct correlation of tree-ring widths with rainfall. Such doubts have been put forward before by Glock (1955) whose studies have been aimed at separating the various effects of seasonal occurrence of precipitation, the amount falling in various seasons, and other climatic factors in their relative influence on tree-ring widths. At present, then, tree-ring widths may be considered more satisfactory for reading chronology than for reading climate. It is this concern about direct correlation of tree-ring width with climate that led to initiation of the present study. This work is a preliminary attempt to obtain independent evidence from pollen concerning the probable nature of the vegetation and thus the climate in a period known to be characterized by narrow tree rings.

New Mexico↗
USGS1963

Association and determinacy in geomorphology

You find a rock. It looks like an ordinary piece of flint, broken and rough. On a part of it is a patina whose soft grey color contrasts with the shiny brownish surfaces of conchoidal fracture. You could have found this rock in nearly any kind of an environment almost anyplace in the world. There is nothing distinctive about it. You hand this same piece of rock to a colleague and ask what he can make of it. He considers it soberly before he says, “You know, that could be an artifact.” There springs to mind then a picture of a primitive man, squatting barefoot before a fire warming his hands. The firelight casts his shadow against the cliff below which he crouches. The difference between the reaction before and after the passing thought that this might indeed be the tool of ancient man is the difference between mild disinterest and a kaleidoscope of mental pictures. This difference reflects differences in the associations of thoughts. The present essay is concerned with how associations are used in geologic reasoning, and then with certain philosophic considerations which seem to be influencing the methodology and direction of geomorphology.

Book chapter↗
USGS1963

Conversations on ecology IV

The conversations on ecology have mentioned the pesticide problem, and in such discussion it is easy to lose sight of the basic philosophic view which is an undercurrent in Miss Carson's book. I should like to expand on that philosophic premise and examine some of its implications for planning vegetation management measures as well as other measures for resource development.

The Garden Journal: Journal of the New York Botani↗
USGS1963

Downstream patterns of riverbed scour and fill

Progress has been made in describing riverbed scour and fill at a given stream section. One needs only the data routinely collected at a stream-gaging station to observe scour and fill at that station. However, similar progress has not been made to determine whether or not the scour and fill observed at a given section extends over a relatively long reach of the channel. Gaging stations are generally located too far apart to draw any conclusions as to scour processes between stations. It remains necessary then to establish a sufficient number of cross sections along a channel to describe the downstream pattern of riverbed scour.

Conference Paper↗
USGS1962

The Vigil Network

Those of us who seek to explain the variations in hydrologic phenomena such as may be observed in the occurrence of floods or in changes in the shape of river channels are painfully aware of the lack of adequate data. Our existing data, collected mainly to serve immediate practical needs for water-resources development, usually are deficient in providing information useful for many kinds of scientific inquiry. Hydrologic records are usually obtained on streams that are highly regulated or otherwise put to use, to the neglect of headwater streams better suited to studies of the details of hydrologic processes.

International Association of Scientific Hydrology ↗
USGS1962

The man and the hill

He was sitting on a large slab of rock. As he looked at the cloud of dust hanging hazily on the horizon, the piece of antler and the block of flint he held in his hand hung as if they were suspended from their previous rapid motion. The man gazed intently across the swaying grass which rose in wave-like billows across the distant hills. What was that dust - a herd of buffalo, a band of hunters, or were coyotes chasing the antelope again? After watching for a while he started again to chip the flint with a rapid twisting motion of the bone in his right hand. The little chips of flint fell in the grass before him. It is the same hill but the scene has changed. Seated on the same rock, holding the reins of a saddle horse, a man dressed in buckskin took the fur cap off his head and wiped his brow. He was looking intently across a brown and desolate landscape at a cloud of dust on the far horizon. Was it the hostile tribe of Indians? It could be buffalo. Nervously he kicked at the ground with the deerhide moccasin, pushing the flint chips out of the way. He wiped the dust from his long rifle. What a terrible place - no water, practically no grass, everything bare and brown. Now at sunset, slanting across the hills green with springtime, a cowman sits on a big rock, pushes his sombrero back on his head, and looks across the valley at a large but quiet herd of stock, moving slowly as each steer walks from one lush patch of grass to another, nibbling. Suddenly he stood up. Far on the horizon some dark objects were moving. Is it the sheepmen? Could it be the stage coach from Baggs to the Sweetwater Crossing? Same hill - a gray truck was grinding slowly toward the summit. It pulled up near a small fenced enclosure where there were some instruments painted a bright silver color. A man stepped out of the truck and turned to his younger companion, "You've never found an arrowhead? Maybe you have never thought about it correctly. If you want to find where an Indian camped long ago, put yourself in his place. Where would he sit to chip flint? He would take some high hill above a grassy valley where the breeze would cool him and where he could look across the country, watching for game or for enemies. If I were an Indian, that's what I would do. You change the chart of the rain gage and I am going to walk up to the place where I think he might have sat." He walked over to the crest of the hill and, near a large slab of sandstone, started to pick up pieces of flint. This is an oft-repeated story. A given hill is repeatedly visited, used, loved or hated, protected or marred, by successive generations of men. All these men had characteristics in common. They had a job to do, a livelihood to make; they had their own plans, their own fears, but they were in one way or another connected with the land.

Circular↗
USGS1962

A national network of hydrological benchmarks

We are engaged in great national programs of water control and development. An expanding population demands ever-increasing supplies of the natural resources which are to be found in or upon the landscape soil, water, minerals, food, timber, and fiber. By his works, by his extractions, man's mark upon his environment becomes ever deeper, his effects more indelible. We often read that water tables are falling, that floods are increasing, that springs go dry more often now than in grandfather's time, or that rivers are muddier than before. Such changes, if true, are troublesome but water is a fluctuating resource, responding over time to changes in the environment. A recurring question of our times, and one that we anticipate will be increasingly vexing to posterity, is to know how much of the change in our environment is caused by man and how much is natural. In trying to answer this question we immediately face the insurmountable fact that changes must be measured relative to some standard base or datum. What can we compare against? The most pervasive and probably the most important of the slow and subtle changes result directly or indirectly from variations in climate. Over a shorter or longer period of time, pulsations in precipitation and temperature change the amounts of water that are evaporated or transpired by the soil and vegetation, the amount of water that replenishes soil water, the quantity of water for recharge to ground water and for riverflow. Climatic variations also cause changes in the pattern of erosion, of which some spectacular consequences can be observed in the arid zones. Changes in climatic pattern, through their effects on the hydrologic cycle, on soil, and on vegetation, can produce results remarkably similar to those effected by the works of man.

Circular↗
USGS1962

The concept of entropy in landscape evolution

The concept of entropy is expressed in terms of probability of various states. Entropy treats of the distribution of energy. The principle is introduced that the most probable condition exists when energy in a river system is as uniformly distributed as may be permitted by physical constraints. From these general considerations equations for the longitudinal profiles of rivers are derived that are mathematically comparable to those observed in the field. The most probable river profiles approach the condition in which the downstream rate of production of entropy per unit mass is constant. Hydraulic equations are insufficient to determine the velocity, depths, and slopes of rivers that are themselves authors of their own hydraulic geometries. A solution becomes possible by introducing the concept that the distribution of energy tends toward the most probable. This solution leads to a theoretical definition of the hydraulic geometry of river channels that agrees closely with field observations. The most probable state for certain physical systems can also be illustrated by random-walk models. Average longitudinal profiles and drainage networks were so derived and these have the properties implied by the theory. The drainage networks derived from random walks have some of the principal properties demonstrated by the Horton analysis; specifically, the logarithms of stream length and stream numbers are proportional to stream order.

Professional Paper↗
USGS1962

Rivers

Rivers are both the means and the routes by which the products of continental weathering are carried to the oceans of the world. Except in the most arid areas more water falls as precipitation than is lost by evaporation and transpiration from the land surface to the atmosphere. Thus there is an excess of water, which must flow to the ocean. Rivers, then, are the routes by which this excess water flows to the ultimate base level. The excess of precipitation over evaporation and transpiration provides the flow of rivers and springs, recharges ground-water storage, and is the supply from which man draws water for his needs.

American Scientist↗
USGS1962

Water and the arid zone of the United States

In a pluvial period associated with Wisconsin glaciation the closed basin of the Estancia Valley in New Mexico held a lake which, at its maximum extent, was 150 feet deep and had a surface area of 450 square miles. This basin, with a mean elevation of about 6,000 feet, has at present an annual precipitation of about 14 inches. Estimates have been made of the Pleistocene precipitation necessary to maintain this pluvial lake. Instead of the present annual average of 14 inches it has been variously estimated that the precipitation must have been between 20 and 24 inches. Lakes existed during Pleistocene time in many places in the western United States that are now true deserts - with a precipitation of less than 4 inches - and there is abundant evidence that early man lived on the shores of these lakes. He must have adapted himself to the increasing aridity; this adaptation can be seen even at present in the form of floodwater farming practices, which have been highly developed by the Hopi Indians, particularly in northeastern Arizona. A gradually changing climate is only one, and not the most important, of the changing conditions to which man must gradually adjust in his particular relation to the use of water. The changes in his own culture in conjunction with changes in population density are usually even more important determinants of man’s use of and attitude toward his water supplies. In a desert area of Central Arizona, near Florence, the remains of irrigation systems developed by the aborigines to irrigate the alluvial valley floor with water diverted from the Gila River, which was at that time perennial, have been mapped and partially excavated. Irrigated agriculture was not practised nearly so extensively in the arid portions of the United States as in Persia, India, and many Mediterranean countries, nor was the general culture of indigenous American tribes so highly developed. Even in the simple cultures of the American Indians patterns of adjustment to a changing climate and to a changing culture and population level can be discerned. These patterns include, however crudely, the development of irrigated agriculture, floodwater farming, water storage for both stock and community use, spring development, and even efforts at rain-making through the offices of prayers, rattles, and dances. These same patterns, more complex to be sure, can be seen to have characterized the adjustment of modern culture to the limited water supplies of the arid climates, even including the prayers and rattles. An aspect of the development of American culture in the arid areas is probably typical and may have a counterpart in certain of the underdeveloped areas in other parts of the world at the present time. The local civilization of the arid climate usually does not develop to a very high level in situ. The indigenous cultures are usually transfused with new bursts of energy and knowledge by the incursion of other cultures which have developed in other climes. The cultural advances in the Fertile Crescent of Mesopotamia were gradually influenced by the barbarian invasion, which added much to, as well as detracted from, the locally developing society. Similarly the spurt of civilization which has characterized the arid parts of the United States since 1846 was determined by the superposition of a culture from the eastern United States on the essentially Spanish culture which had been developing since the initial exploration of the southwestern desert in 1630.

Conference Paper↗
USGS1962

Water

What do you use water for? If someone asked you this question you would probably think right away of water for drinking. Then you would think of water for bathing, brushing teeth, flushing the toilet. Your list would get longer as you thought of water for cooking, washing the dishes, running the garbage grinder. Water for lawn watering, for play pools, for swimming pools, for washing the car and the dog. Water for washing machines and for air conditioning. You can hardly do without water for fun and pleasure—water for swimming, boating, fishing, water-skiing, and skin diving. In school or the public library, you need water to wash your hands, or to have a drink. If your home or school bursts into flames, quantities of water are needed to put it out. In fact, life to Americans is unthinkable without large supplies of fresh, clean water. If you give the matter a little thought, you will realize that people in many countries, even in our own, may suffer from disease and dirt simply because their homes are not equipped with running water. Imagine your own town if for some reason - an explosion, perhaps - water service were cut off for a week or several weeks. You would have to drive or walk to a neighboring town and bring water back in pails. Certainly if people had to carry water themselves they might not be inclined to bathe very often; washing clothes would be a real chore. Nothing can live without water. The earth is covered by water over three-fourths of its surface - water as a liquid in rivers, lakes and oceans, and water as ice and snow on the tops of high mountains and in the polar regions. Only one-quarter of our bodies is bone and muscle; the other three-fourths is made of water. We need water to live, and so do plants and animals. People and animals can live a long time without food, but without water they die in a few days. Without water, everything would die, and the world would turn into a huge desert.

Book↗
USGS1961

Philosophy for water development

There is probably no one in this room who has not had an experience analogous to the one I here describe. You sat at the dinner table next to a nice lady who impressed you with her breadth of interest in community affairs. She said to you "Oh, you work in the field of water resources. That certainly is a major problem facing the United States, isn't it? You know, we have had long discussions about this matter in a club to which I belong. We have made a considerable study of this matter and all of us are convinced that a key element in the survival of America is to find a solution to our water problem. "You know," she said, "there are certainly a lot of different kinds of organizations mixing up in the field of water. They all seem to be running off in different directions. It seems to me that one of the things we need most is a national water policy. Don't you think so?” I know how you answered the question. You must have about got started on a discussion of some of the complications when the conversation turned to the question of how long did it take you to get home in that last big snow. So, in effect, you continue to talk about the water problem even if merely as you exchange pleasantries about the day's weather. But then you went home and you thought some more about what the nice lady said and you asked yourself "well, now, truly how do we solve the Nation's water problem? What has a national water policy to do with a solution of this problem?" In the next few minutes I wish to exchange with you some of our thoughts on this matter.

Conference Paper↗
USGS1960

River meanders

Most river curves have nearly the same value of the ratio of curvature radius to channel width, in the range of 2 to 3. Meanders formed by meltwater on the surface of glaciers, and by the main current of the Gulf Stream, have a relation of meander length to channel width similar to rivers. Because such meanders carry no sediment, the shapes of curves in rivers are evidently determined primarily by the dynamics of flow rather than by relation to debris load. Velocity distributions along river curves provide a generalized picture of flow characteristics. Evidence on flow resistance in curved channels suggests that a basic aspect of meander mechanics may be related to the distribution of energy loss provided by a particular configuration or curvature. No general theory of meanders is as yet satisfactory, however; in fact, present evidence suggests that no single theory will explain the formation and characteristics of all meanders and that few of the physical principles involved have yet been clearly identified.

Geological Society of America Bulletin↗
USGS1960

A primer on water

When you open the faucet you expect water to flow. And you expect it to flow night or day, summer or winter, whether you want to fill a glass or water the lawn. It should be clean and pure, without any odor. You have seen or read about places where the water doesn't have these qualities. You may have lived in a city where you were allowed to water the lawn only during a few hours of certain days. We know a large town where the water turns brown after every big rainstorm. Beginning shortly after World War II, large areas in the Southwestern United States had a 10-year drought, and newspapers published a lot of information about its effects. Some people say that the growing demand for water will cause serious shortages over much of the country in the next 10 to 40 years. But it has always been true that while water wells and springs dry up in some places, floods may be occurring in other places at the same time. Nearly every month news stories are published describing floods somewhere in the country. In fact, every year, on the average, 75,000 persons are forced from their homes by floods. In some years, as in 1951 when the lower Kansas River experienced a great flood, half a million people are affected. To understand the reasons for such recurring distress, it is necessary to know something about rivers and about the flat land or flood plain that borders the river. Interest in water and related problems is growing as our population increases and as the use of water becomes steadily greater. To help meet this heightened interest in general information about water and its use and control is the reason this primer was written. The primer is in two parts. The first part tells about hydrology, or the science that concerns the relation of water to our earth, and the second part describes the development of water supplies and the use of water. The Geological Survey is publishing this primer in nontechnical language in the hope that it will enable the general reader to understand the facts about water as a part of nature, and that by having this understanding the people can solve their water problems. We, as representatives of the Geological Survey, acknowledge with thanks the helpful suggestions made on an early draft by Marion Loizeaux, Maria Lord Converse, Constance Foley, Laura R. Langbein, and Bruce C. Leopold. We are also indebted to various geologists and engineers of the Survey for their discerning critical reviews.

General Interest Publication↗
USGS1960

Conservation and protection

When I was a child we had a burro I called Gacho. He was a typical burro, omnivorous in his eating habits and prone to streaks of extreme recalcitrance. Our yard wasn't very large, but it did produce enough grass and weeds to keep old Gacho in good fettle. His first preference was for the native grasses, and he chose to graze the lush patches rather than the shriveled plants on the areas of thin soil. Nevertheless, he was not particular and seemed to graze to some extent all over the yard. He often nibbled in the flower beds and I sometimes wondered whether he did this just for spite. After a time I arranged some crude fences and a tethering rope to keep him out of the most important flower beds. The yard was so small that we had a waste problem. To ignore the problem would hardly have been civilized, but, on the other hand, one couldn't follow him around all day with a shovel. So a workable compromise was adopted by keeping him penned up at night in a small enclosure, which, of course, could not be kept immaculate but was at least reasonably clean. We had the burro and we weren't getting rid of him. He was useful; we enjoyed riding him and hitching him up to our wagons. But he was a bother sometimes. Here was a simple case of resource use and resource development. The case is incomplete, but it demonstrates a principle. The resource, represented by the vegetation, was being utilized, or developed if you will, by a small juggernaut which was only partly controllable by my youthful skills. There was no need to urge utilization. That followed as a matter of course. The problem was that the one who utilized the resource, in this case the burro, was not very discerning of relative values. To Gacho the choice of which plant to eat and where to get rid of the waste was governed only by his own interests and convenience. Now, when a planning body convenes, one may bet that either the burro has Jain down in a flower bed or he has messed up the yard. By this time everybody is already in a lather. An appreciation of the existence of problems usually leads to a period of organizing the facts, assessing the current situation, and surveying the future possibilities. In the New England area such an assessment has recently been completed. Since that stage has been reached, it is logical to discuss the function of a planning unit as a prelude to the next phase. I should like to outline my own thoughts on this matter, but I do so without expecting to convince all others.

Circular↗