Geology topics

Luna Bergere Leopold

Publications and source records attributed to Luna Bergere Leopold.

At least 19 recordsLinked to original sources

USGS2014

Rainfall frequency: An aspect of climatic variation

Analyses which have been made in the past have shown no significant trend in annual values of rainfall during the period of rainfall records in the southwestern United States. In the present study, frequency of daily rains of various sizes are analyzed for four long-record stations in New Mexico. It is shown that the frequency of rains smaller than 0.50 inch in a day progressively increased from 1850 to about 1930. Opposite trends in different size classes tended to partially compensate one another in such a way that trends do not appear in the annual rainfall totals. Frequency of rains of various sizes comprising wet years and dry are compared. Some effects of changes in rainfall frequency on vegetation and erosion are discussed.

New Mexico↗

USGS2014

River meanders and vorticity theorem

T he serpentine windings of rivers, which in certain reaches attain a remarkable symmetry and are then called meanders, must represent one aspect of the tendency for establishment of quasi-equilibrium in natural streams. With the increase in knowledge of the interaction of forces operating in rivers, this tendency toward equilibrium has assumed a greater significance.

Eos, Earth and Space Science News↗

USGS2010

On the quantitative inventory of the riverscape

In the vicinity of Berkeley, California, 24 minor valleys were described in terms of factors chosen to represent aspects of the river landscape. A total of 28 factors were evaluated at each site. Some were directly measurable, others were estimated, but each observation was assigned to one of five categories for that factor. Each factor for each site was then expressed as a uniqueness ratio, which depended on the number of sites being in the same category. The uniqueness ratio is believed to represent one way the scarcity of a given riverscape can be ranked quantitatively without bias based on notions of good or bad, and without assigning monetary value.

California↗

USGS2010

An improved method for size distribution of stream bed gravel

Random sampling of surface rocks on a gravel bar is biased toward larger sizes which, because of their area, are more likely to be picked up. Weighting can eliminate this bias. Data on average weight of a single rock are used to change numbers of rocks to weights, thus yielding size frequency data in general agreement with a sieved and weighed sample. The question of what to sample depends on the use to which the data are to be put, and is not treated in detail in this paper.

Water Resources Research↗

USGS2009

The Vigil Network: A means of observing landscape change in drainage basins

Long-term monitoring of geomorphic, hydrological, and biological characteristics of landscapes provides an effective means of relating observed change to possible causes of the change. Identification of changes in basin characteristics, especially in arid areas where the response to altered climate or land use is generally rapid and readily apparent, might provide the initial direct indications that factors such as global warming and cultural impacts have affected the environment. The Vigil Network provides an opportunity for earth and life scientists to participate in a systematic monitoring effort to detect landscape changes over time, and to relate such changes to possible causes. The Vigil Network is an ever-increasing group of sites and basins used to monitor landscape features with as much as 50 years of documented geomorphic and related observations.

Hydrological Sciences Journal↗

USGS2005

Channel and hillslope processes revisited in the Arroyo de los Frijoles watershed near Santa Fe, New Mexico

Detailed documentation of geomorphic changes in the landscape of more than a few years is rarely possible. Channel cross sections, channel profiles, sediment deposition behind dams, and hillslope-erosion plots, originally benchmarked within several watersheds outside Santa Fe, New Mexico, in the 1950’s and 1960’s, for a 1966 report that documented processes and rates of arid-region sediment production and deposition, were resurveyed in the mid-1990’s. Many of the original study sites were relocated and surveyed in the mid-1990’s to determine subsequent channel and hillslope changes and to determine whether trends of channel and hillslope aggradation and degradation that were evident in the 1950’s and 1960’s have continued. In general, the net change in channel geometry has been small over the last 30–40 years. The average change in cross-sectional area of 32 resurveyed cross sections was erosion of 0.27 square meter, which equates to a 4-percent increase in cross-sectional area. The average net change in thalweg elevation for 51 resurveyed cross sections was degradation of 0.04 meter. Unpublished data (1964–68) from the scour chains showed that 371 chains had an average scour of 0.14 ± 0.14 meter and that 372 chains showed an average fill of 0.13 + 0.11 meter. Scour, found in the original study (1958–64) to be proportional to the square root of discharge, was confirmed with the addition of unpublished data (1964–68). The observed channel changes have no consistent trend, compared either to results observed in the original 1966 study or to distance from the watershed divide. The conclusion drawn in the original study was that most channels were aggrading; the resurvey showed that aggradation did not continue. An increase in housing and population in the Arroyo de los Frijoles watershed since the 1950’s has led to more roads. Channel degradation is most noticeable at road crossings. The greatest degradation of the main channel Arroyo de los Frijoles, 1.53 meters, and the greatest aggradation, 0.38 meter, occur downstream and upstream, respectively, from a culvert in a dirt road. Periods of high average annual rainfall intensity reported for Santa Fe for 1853–80 immediately preceded late 19th century arroyo incision, and another period of high-intensity rainfall began in 1967. This may indicate that climatic factors are again favorable for arroyo incision in this part of New Mexico; data from this resurvey, however, do not provide evidence of a renewed cycle of erosion. At a 1930’s Civilian Conservation Corps-constructed dam on Coyote C. Arroyo, the measured sediment yield from 1966 to 1993 was 139 metric tonnes per square kilometer per year. Sediment yields have decreased through time because of either a decrease in the trap efficiency of the reservoir over time or a decrease in sediment delivery to the reservoir because of upstream channel storage. The effects of base-level rise on the channel profile were documented in 1993 through resurveys of sediment deposits behind two small dams, Big Sweat Dam and Little Sweat Dam. Both dams, built in 1960, showed sediment deposition that extends 20 and 9.3 meters upstream, respectively, and the 1993 sediment gradient was nearly the same as the unaffected channel upstream. Big Sweat Dam showed fluctuations in channel gradient within 5.3 meters of the dam, which may be a result of local scour following complete filling of the dam, scour from increased sinuosity, or differences in the location of surveying stations over time. The sinuosity of the channel has increased over time, presumably from a reduction in slope. Channel gradients 0 to 11.0 meters upstream from Little Sweat Dam have remained constant at about 0.028 from 1964 to 1993. Measurement of erosion or hillslope-erosion plots show that average values of surface erosion range from 0.019 to 0.096 centimeters per year and are within values reported for regional erosion and denudation studies. Sediment yield from the Slopewash Tributary erosion plot was 307 metric tonnes per square kilometer per year. The reproducibility and accuracy of the resurveys from the 1950’s to the 1990’s attest to the concepts used to quantify geomorphic features established in the Vigil Network. With relatively simple techniques, more than 30 years of geomorphic change were observed in this study.

New Mexico↗

USGS2004

Data and understanding

In the year 1534 when Cabeza de Vaca escaped from the aborigines of southern Texas by whom he had been enslaved for six years, he made his way on foot from the vicinity of Galveston to the west coast of Mexico. Although his Relación was not printed until 1542, the verbal report of Cabeza de Vaca gave impetus to the growing interest in exploration of New Spain. Estevanico, the black, one of de Vaca's companions, served as guide to Fray Marcos de Niza on the first Spanish reconnaissance to reach the village of Zuni in New Mexico. The earliest Spanish exploring parties hoped to find riches, but expected to acquire, at the least, facts. These "gentlemen of high quality," as Castaneda called them, wanted to see for themselves whether the cities of Cibola had streets of silver. Hearsay was not enough. Rumor was to be replaced by first-hand knowledge. Without discounting the hope for personal gain, these men presumably were fired with some further intellectual and spiritual motivation, among which must have been the desire for facts about these parts where we are assembled. Inscription Rock, only a few miles west of Albuquerque, bears illuminating tidbits of history. Don Diego de Vargas, says the carved inscription of 1692, came here "A su costa"—at his own expense. We are attempting to survey and correlate some of the facts which people have gained about the nature of semi-arid lands. We are better off than the early Spanish explorers, for in the intervening period data and information have been accumulated in scope and in detail beyond the imagination of our predecessors. We have available excellent maps, knowledge of the soils and of the rocks, both at the surface and below the ground, measurements of precipitation, descriptions of the vegetation, data on the flow of streams, experience in the use, if not the husbandry, of the land. It is true that for the purposes of our complex civilization, the need for additional data has far outstripped the programs of fact-finding. But it appears that an indefinite expansion of the collection of routine measurements would still leave something lacking. I draw the distinction between measurement data and understanding; between the collection of facts and knowledge of processes and interrelationships. Although we have a wealth of data, our understanding of the semi-arid environment is poor. Understanding the physical and biologic processes operating in an environment is important for living in and with the land. As an example, let us look briefly at the interrelation of the water and sediment in ephemeral streams, and the problem of valley trenching or arroyo cutting.

Conference Paper↗

USGS1997

Bedload and river hydraulics - Inferences from the East Fork River, Wyoming

During 1973-79, bedload data were collected in a sophisticated trap on a river of moderate size, the East Fork. The transport rate was measured most days through a full snowmelt season, and the rate was determined separately for eight zones across the channel width. The quantitative data are unique and unlikely to be repeated. Nor need they be, because as a result of this effort a practical bedload sampler was adequately tested against full river measurement. It was shown that bedload moves sporadically and randomly on the river bed. Therefore, transport rate is highly variable in short periods of time. There is also a wide variance from day to day. Yet, different rivers have transport rates, which are functions of discharge, depth, and sediment size, that are clearly distinct. Comparison of computed and measured transport rates indicates that a major problem remains: What grain size is representative of the bedload when there is a wide or heterogeneous particle-size distribution? Size of the bedload in motion may be very different from the size of bed material obtained from samples of the streambed. For general computation, the river channel slope may be averaged, and it may be assumed that water-surface slope does not change materially with changing discharge. Indeed, this generality is correct, in that, compared with depth, velocity, and width, slope is conservative at-a-station. However, in more detail, slope changes importantly with discharge in short reaches of channel, and those changes are very different in pool and riffle. These local changes in slope are not merely an aspect of a detailed longitudinal profile but involve cross-channel as well as down-channel components. The pool and riffle sequence involves not only undulation of bed elevation and bar formation on alternate sides of the channel, but alternation of the zone of superovulation of the water surface, and changing relation of watersurface slope to discharge. These details can be seen only in the full topography of the water surface. Riffles fill during high flow and scour at low flow. Changes in local water-surface slope illustrate this process. Pools are a storage zone for sediment in the low-flow season. Even though large volumes of sediment move, the distance moved is not large—in the East Fork River, sand of size 0.5-1 millimeter moved 650 meters during the 1979 snowmelt runoff season. Bedload transport is greatest over or near bars and not in the deepest part of the channel. Direct observation of the locus of sediment transport indicates that this locus moves from one side of the channel to the other in concert with the occurrence of alternate bars. Separately, data indicate that at constant stream power, transport rate increases as depth decreases.

Wyoming↗

USGS1976

Data for calibrating unsteady-flow sediment-transport models, East Fork River, Wyoming, 1975

In 1975, data to calibrate a one-dimensional unsteady-flow and sediment-transport routing model were collected on a reach of the East Fork River of western Wyoming. The reach, 3.1 miles (5 kilometers) in length, wan immediately upstream from a previously established bedload sampling station. Nineteen channel cross sections were sounded at regular intervals during the spring-runoff period. Four stage recorders provided continuous records of water-surface elevations. Samples of bed material at most of the cross sections were obtained prior to high water. Streamflow and sediment-discharge measurements were collected at four of the sections. The physiography and hydrology of the contributing watershed, the study reach, and the equipment and techniques used in data collection are described briefly. The bulk of the report is a presentation of data for the several-week period of late May to early June 1975, for which concurrent water discharge data, bedload transport and size data, and cross-section depth measurements were collected. In addition, some data collected in 1973 and 1974 and before and after the calibration period in 1975 are included for completeness.

Wyoming↗

USGS1973

River channel change with time : An example

Monumented channel cross sections were resurveyed over a period of 20 yrs (1953 to 1972) to determine the amount and kind of change of channel area and position on a 3.7-sq-mi basin, Watts Branch near Rockville, Maryland. For the first 12 yrs, the channel progressively but slowly became smaller as urbanization of the basin gradually proceeded. After 1966, a threshold of change apparently was passed and, probably as a result of an increased rate of land alteration upstream, large amounts of sediment were deposited within the channel and overbank. The number of floods exceeding channel capacity increased dramatically from an average of two to more than ten per year. Simultaneously, the channel area began to increase. Despite the trend toward increasing cross-sectional area, the net result after 20 yrs was a channel smaller by 20 percent than it had been originally. Urbanization did not alter the rate of channel migration.

Maryland↗

USGS1972

Some rates of geomorphological processes

This brief report summarizes three sets of measurement data on certain processes. The first concerns the rate of movement of soil on hillslopes, especially by mass movement or slow gravitational creep. The results are abstracted from an unpublished manuscript by the junior author who reports on the measurements which Leopold began 10 or more years ago and to which in more recent years Emmett has added new sites and has carried on the annual remeasurement. The results are those from "mass-movement lines", which consist of a series of pins or iron rods, 10 inches (25 cm) long driven vertically into the ground along a straight line-of-sight, secured at each end with stiff iron posts. The Survey consists of setting a theodolite over one of the end bench marks and orienting on the other. The distance of each individual pin from the line of sight is recorded. Resurveys are usually made annually.

Geographia Polonica↗

USGS1971

Trees and streams: The efficiency of branching patterns

Extending the analysis of branching patterns of the drainage net of rivers, originated by Horton, the relation of average numbers and lengths of tree branches to size of branch was investigated. Size of branch was defined by branch order, or its position in the hierarchy of tributaries. It was found that, as in river drainage nets, there is a definite logarithmic relation between branch order and lengths and numbers. This definite relation is quantitatively comparable, within limits, among river networks, tree branching systems, and several random-walk models in both two and three dimensions. Such a relation appears to be the most probable under the applicable constraints. Moreover the most probable arrangement appears to minimize the total length of all stems in the branching system within other constraints and so, to that extent, achieves a certain efficiency.

Journal of Theoretical Biology↗

USGS1971

A procedure for evaluating environmental impact

In a recent article in "Science" discussing the Environmental Policy Act of 1969, Gillette (1971) states "The law's instructions for preparing an impact report apparently are not specific enough to insure that an agency will fully, or even usefully, examine the environmental effects of the projects it plans." This report contains a procedure that may assist in developing uniform environmental impact statements. The Department of the Interior and the Council on Environmental Quality will appreciate comments on the procedure here proposed. The heart of the system is a matrix which is general enough to be used as a reference checklist or a reminder of the full range of actions and impacts on the environment that may relate to proposed actions. The marked matrix also serves as an abstract of the text of the environmental assessment to enable the many reviewers of impact reports to determine quickly what are considered to be the significant impacts and their relative importance as evaluated by the originator of the impact report. Many exhaustive studies of the use of matrices for environmental studies are now being undertaken. (See Sorensen, 1971.) This comparatively simple system is intended as a guide for the many people who are faced with the evaluation and preparation of environmental impact reports before the results of these studies have been completed. It should be borne in mind that there is presently no uniformity in approach or agreement upon objectives in an impact analysis and this generalized matrix is a step in that direction. The procedure does not limit the development of detail in any specific aspect of the environment; a separate expanded matrix for any environmental aspect can easily be developed within the framework provided.

Circular↗

USGS1971

Hydrology of two small river basins in Pennsylvania before urbanization, with a section on observation of stream fauna

Basic data on water quantity, chemical quality, and suspended sediment are tabulated to record the conditions existing in two basins near Philadelphia, each about 32 square miles in area. The basins in 1970 are agricultural land for the most part, but urban and industrial development is imminent as the Philadelphia metropolitan area expands. Hopefully, as changes caused by urbanization occur in future years, data published herein will be useful as a base for comparison. Pickering Creek basin has a higher population than the upper East Branch Brandywine Creek basin. The two are comparable in discharge characteristics and in shapes and sizes of channels, but the Pickering Creek basin is producing a considerably larger suspended-sediment load. Also the effects of urbanization are discernible in some chemical parameters. During the study, a small subbasin, one-half square mile in area, was converted from agricultural use to an industrial park. This change resulted in a marked increase in sulfates, nitrates, chlorides, and dissolved solids in the streamflow.

Pennsylvania↗

USGS1970

Hydrologic research on instrumented watersheds

The successful research man is the one who asks himself the right question. Research must go on primarily in the mind and only secondarily in the physical and biological world. It is only too easy to confuse the choice of a proper tool and the choice of a proper question. Some tools are quite unsuited to certain questions and some questions cannot be answered without the appropriate tool. There has been in recent years a large amount of discussion about whether the high costs and the extensive time period required for experimental watershed* research is really worth the investment. Recent discussions of this matter have cited as major criticisms of the instrumented basin that they are expensive, they leak water, they are unrepresentative, they produce changes too small for detection, and it is difficult to transfer the results. (See Hewlett, Lull, and Reinhart, 1969.) These are all questions worth talking about, but in one sense they tend to obscure the main issue. The main issue is what do we want to learn? If we can decide what it is we want to know, then we can logically ask ourselves what is the best way of going about obtaining that knowledge. It is in this context that we are most likely to place the experimental watershed in a useful and logical position in a classification of research methods.

Conference Paper↗

USGS1970

Let's Sing 'Auld Lang Syne' for the Upper Brandywine: Or, to continue with Burns, how the best laid environmental schemes of men "gang aft a-gley"

Perhaps the most lamentable mistake that one can make is to be right too soon. This was the story of the Brandywine Plan, an attempt to organize local people for the permanent protection of the environmental amenities of their own land. The Upper East Branch of Brandywine Creek drains a rolling basin of farms, fields, woodlands, and a sprinkling of residential areas. Because it lies at the far edge of the commuting range to the population centers of Philadelphia and Wilmington, the basin's natural beauty has barely been touched by the blight of suburban sprawl. The waters of its streams are clear; its ample woodlands and fields are filled with wildlife. Driving slowly through the basin's winding roads and across its narrow bridges evokes the feeling of a pastoral painting, of the ideal landscape of rural eastern America. For two years, I had the privilege of working closely with a group preparing a land plan for the Brandywine area. The plan was designed to offer the inhabitants of the basin a feasible way to preserve forever the natural qualities of their region from the inevitable wave of urbanization. A report in Science magazine called it the perfect plan that failed.

Natural History↗

USGS1969

Quantitative comparison of some aesthetic factors among rivers

It is difficult to evaluate the factors contributing to aesthetic or nonmonetary aspects of a landscape. In contrast, aspects which lend themselves to cost-benefit comparisons are now treated in a routine way. As a result, nonmonetary values are described either in emotion-loaded words or else are mentioned and thence forgotten. The present report is a preliminary attempt to quantify some elements of aesthetic appeal while eliminating, insofar as possible, value judgments or personal preferences. If methods of recording such factors can be developed, the results promise to be a useful, new kind of basic data needed in many planning and decision-making circumstances. Such data would be especially useful when choices must be made among alternative courses of action. Such data would tend to provide a more prominent consideration of the nonmonetary aspects of a landscape. Assignment of quantitative estimates to aesthetic factors leads not so much to ratios of value as to relative rank positions. In fact, value itself tends to carry a connotation of preference, whereas ranking can more easily be used for categorization without attribution of preference and thus it tends to a void the introduction at too early a stage of differences in preference. Because the Federal Power Commission has been studying an application for a permit to construct one or more additional hydropower dams in the vicinity of Hells Canyon of the Snake River, the localities studied for the present discussion are in that region of Idaho. Hopefully, the data collected will provide some useful information on factors related to nonmonetary values in the region. The present discussion has been kept free of the preference judgments of the writer, and throughout the discussions observations are treated as facts.

Idaho↗

USGS1969

The Colorado River region and John Wesley Powell

A century ago John Wesley Powell-teacher, scientist, and veteran of the Civil War-set out to explore the unknown reaches of the Colorado River. He emerged from the forbidding canyons with a compelling interest in the nature of the western lands and how they could be developed for the greatest benefit to the Nation. A man gifted with imagination, yet always tempered by the scientist's appreciation for facts, Powell became one of the country's most vigorous proponents for the orderly development of the public domain and the wise use of its natural resources. Throughout his lifetime, Powell stood firm in his belief that science, as a sound basis for human progress, should serve all the people, and he played an important role in organizing and directing scientific activities of the U.S. Government. His zeal led to the establishment of the Geological Survey in the U.S. Department of the Interior and the Bureau of Ethnology in the Smithsonian Institution. On this 100th Anniversary of the Powell Colorado River Expedition, the U.S. Department of the Interior, Smithsonian Institution, and National Geographic Society (which Powell helped to found) have joined many organizations and individuals to recall the works of this man ;and to examine anew the imprints of his mind. His prescient concepts for the Nation's programs concerning people and their environment have been enhanced through a century of national development.

Colorado River↗