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Geology topics

W. R. Osterkamp

Publications and source records attributed to W. R. Osterkamp.

At least 37 records · Page 2Linked to original sources
USGS2000

The disparity between extreme rainfall events and rare floods - with emphasis on the semi-arid American West

Research beginning 40 years ago suggested that semi-arid lands of the USA have higher unit discharges for a given recurrence interval than occur in other areas. Convincing documentation and arguments for this suspicion, however, were not presented. Thus, records of measured rainfall intensities for specified durations and recurrence intervals, and theoretical depths of probable maximum precipitation for specified recurrence intervals and areal scales are considered here for comparing extreme rainfalls of semi-arid areas with those of other climatic areas. Runoff from semi-arid lands, as peaks of rare floods, is compared with that of other areas using various published records. Relative to humid areas, semi-arid parts of the conterminous USA have lower 100-year, 6-h rainfall intensities and smaller depths of 100-year probable maximum precipitation for 26-km 2 areas. Nonetheless, maximum flood peaks, flash-flood potentials, and runoff potentials are generally larger in semi-arid areas than in more humid parts of the nation. Causes of this disparity between rainfall and runoff appear to be results of soil and vegetation that in humid areas absorb and intercept rainfall and attenuate runoff, but in semi-arid areas limit infiltration and enhance runoff from bare, crusted surfaces. These differences in soil and vegetation conditions are indicated by the relatively high curve numbers and drainage densities that are typical of semi-arid areas. Owing to soil and vegetation conditions, rare floods in semi-arid areas are more likely to cause landform change than are floods of similar magnitude elsewhere.

Hydrological Processes↗
USGS2000

Classification of river regimes: A context for hydroecology

Over the past 30 years, ecologists have demostrated the importance of flow and temperature as primary variables in driving running water, riparian and floodplain ecosystems. As it is important to assess the size and timing of discharge variations in relation to those in temperature, a method is proposed that uses multivariate techniques to separately classify annual discharge and temperature regimes according to their 'shape' and 'magnitude', and which then combines the classifications. This paper: (i) describes a generally applicable method; (ii) tests the method by applying it to riparian systems on four British rivers using a 20-year record (1977-97) of flow and air temperature: (iii) proposes a hydroecological interpretation of the classification; (iv) considers the degree to which the methodology might provide information to support the design of ecologically acceptable flow regimes. 'Regimes' are defined for discharge and air temperature using monthly mean data. The results of applying the classification procedure to four British rivers indicates that the 'typical' regimes for each of the four catchments are composite features produced by a small number of clearly defined annual types that reflect interannual variability in hydroclimatological conditions. Annual discharge patterns are dominated by three 'shape' classes (accounting for 94% of the station years: class A, early (November) peak; class B, intermediate (December-January) peak; and class C, late (March) peak) and one 'magnitude' class (70% of the station years fall into class 3, intermediate), with two subordinate 'magnitude' classes: low-flow years (18%) and high flow years (12%). For air temperature, annual patterns are classified evenly into three 'shape' and four 'magnitude' classes. It is argued that this variety of flow-temperature patterns is important for sustaining ecosystem integrity and for establishing benchmark flow regimes and associated frequencies to aid river management. Copyright ?? 2000 John Wiley & Sons, Ltd.Over the past 30 years, ecologists have demonstrated the importance of flow and temperature as primary variables in driving running water, riparian and floodplain ecosystems. As it is important to assess the size and timing of discharge variations in relation to those in temperature, a method is proposed that uses multivariate techniques to separately classify annual discharge and temperature regimes according to their `shape' and `magnitude', and which then combines the classifications. This paper: (i) describes a generally applicable method; (ii) tests the method by applying it to riparian systems on four British rivers using a 20-year record (1977-97) of flow and air temperature; (iii) proposes a hydroecological interpretation of the classification; (iv) considers the degree to which the methodology might provide information to support the design of ecologically acceptable flow regimes. `Regimes' are defined for discharge and air temperature using monthly mean data. The results of applying the classification procedure to four British rivers indicates that the `typical' regimes for each of the four catchments are composite features produced by a small number of clearly defined annual types that reflect interannual variability in hydroclimatological conditions. Annual discharge patterns are dominated by three `shape' classes (accounting for 94% of the station years: class A, early (November) peak; class B, intermediate (December-January) peak; and class C, late (March) peak) and one `magnitude' class (70% of the station years fall into class 3, intermediate), with two subordinate `magnitude' classes: low-flow years (18%) and high flow years (12%). For air temperature, annual patterns are classified evenly into three `shape' and four `magnitude' classes. It is argued that this variety of flow-temperature patterns is important for sustaining ecosystem integrity and for establishing benchmark flow regimes and associated frequencies to aid

Hydrological Processes↗
USGS1998

Processes of fluvial island formation, with examples from Plum Creek, Colorado and Snake River, Idaho

A fluvial island is a landform, elevated above and surrounded by stream-channel branches or waterways, that persists sufficiently long to establish permanent vegetation. Natural fluvial islands occur in any part of a drainage network but most commonly in montane, piedmont-valley, and coastal flood-plain environments. Processes, often interactive, by which islands form include avulsion (the sudden separation of land by a flood or by an abrupt change in the course of a stream), rapid and gradual channel incision, channel migration, dissection of both rapidly and slowly deposited bed sediment, and deposition of bed sediment on a vegetated surface or behind a channel obstruction. Products of high-energy conditions, fluvial islands typically lack stability over decades to millennia. Fluvial islands in Plum Creek, Colorado, USA, results of sorting processes following a recent high-magnitude flood, and in the Snake River, Idaho, USA, partly results of the Pleistocene Bonneville Flood, illustrate how islands form, develop, and disappear. The examples consider differing conditions of island shape, size, height, sediment, and vegetation.

Colorado, Idaho↗
USGS1998

Downstream effects of dams on channel geometry and bottomland vegetation: Regional patterns in the Great Plains

The response of rivers and riparian forests to upstream dams shows a regional pattern related to physiographic and climatic factors that influence channel geometry. We carried out a spatial analysis of the response of channel geometry to 35 dams in the Great Plains and Central Lowlands, USA. The principal response of a braided channel to an upstream dam is channel-narrowing, and the principal response of a meandering channel is a reduction in channel migration rate. Prior to water management, braided channels were most common in the southwestern Plains where sand is abundant, whereas meandering channels were most common in the northern and eastern Plains. The dominant response to upstream dams has been channel-narrowing in the southwestern Plains (e.g., six of nine cases in the High Plains) and reduction in migration rate in the north and east (e.g., all of twelve cases in the Missouri Plateau and Western Lake Regions). Channel-narrowing is associated with a burst of establishment of native and exotic woody riparian pioneer species on the former channel bed. In contrast, reduction in channel migration rate is associated with a decrease in reproduction of woody riparian pioneers. Thus, riparian pioneer forests along large rivers in the southwestern Plains have temporarily increased following dam construction while such forests in the north and east have decreased. These patterns explain apparent contradictions in conclusions of studies that focused on single rivers or small regions and provide a framework for predicting effects of dams on large rivers in the Great Plains and elsewhere. These conclusions are valid only for large rivers. A spatial analysis of channel width along 286 streams ranging in mean annual discharge from 0.004 to 1370 cubic meters per second did not produce the same clear regional pattern, in part because the channel geometries of small and large streams are affected differently by a sandy watershed.

Great Plains↗
USGS1997

Geomorphic considerations for erosion prediction

Current soil-erosion prediction technology addresses processes of rainsplash, overland-flow sediment transport, and rill erosion in small watersheds. The effects of factors determining sediment yield from larger-scale drainage basins, in which sediment movement is controlled by the combined small-scale processes and a complex set of channel and other basin-scale sediment-delivery processes, such as soil creep, bioturbation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated. General suggestions are provided for the development of erosion-prediction technology at the geomorphic or drainage-basin scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss. An emerging technology must consider: (1) the effects on sediment yield of climate, geology and soils, topography, biotic interactions with other soil processes, and land-use practices; (2) all processes of sediment delivery to a channel system; and (3) the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction.

Environmental Geology↗
USGS1996

Riparian vegetation and fluvial geomorphic processes

Riparian vegetation and fluvial-geomorphic processes and landforms are intimately connected parts of the bottomland landscape. Relations among vegetation, processes, and landforms are described here for representative streams of four areas of the United States: high-gradient streams of the humid east, coastal-plain streams. Great Plains streams, and stream channels of the southwestern United States. Vegetation patterns suggest that species distributions in the humid east are largely controlled by frequency, duration, and intensity of floods. Along channelized streams, vegetation distribution is largely controlled by variation in fluvial geomorphic processes (cycles of degradation and aggradation) in response to increases in channel gradient associated with channelization. Similarly, riparian vegetation of Great Plains streams may be controlled by fluxes in sediment deposition and erosion along braided streams. Patterns of riparian vegetation in semi-arid regions may be most closely related to patterns of water availability, unlike most other streams in more humid environments. Channel-equilibrium conditions control stability of the coincident fluvial landform and attendant vegetation pattern throughout the continent. In most situations, riparian-vegetation patterns are indicative of specific landforms and, thus, of ambient hydrogeomorphic conditions.

Geomorphology↗
USGS1996

The role of vegetation and bed-level fluctuations in the process of channel narrowing

A catastrophic flood in 1965 on Plum Creek, a perennial sandbed stream in the western Great Plains, removed most of the bottomland vegetation and transformed the single-thalweg stream into a wider, braided channel. Following eight years of further widening associated with minor high flows, a process of channel narrowing began in 1973; narrowing continues today. The history of channel narrowing was reconstructed by counting the annual rings of 129 trees and shrubs along a 5-km reach of Plum Creek near Louviers, Colorado. Sixty-three of these plants were excavated in order to determine the age and elevation of the germination point. The reconstructed record of channel change was verified from historical aerial photographs, and then compared to sediment stratigraphy and records of discharge and bed elevation from a streamflow gaging station in the study reach. Channel narrowing at Plum Creek occurs in two ways. First, during periods of high flow, sand and fine gravel are delivered to the channel, temporarily raising the general bed-level. Subsequently, several years of uninterrupted low flows incise a narrower channel. Second, during years of low flow, vegetation becomes established on the subaerial part of the present channel bed. In both cases, surfaces stabilize as a result of vegetation growth and vertical accretion of sediment.

Geomorphology↗
USGS1996

Channel narrowing and vegetation development following a great plains flood

Streams in the plains of eastern Colorado are prone to intense floods following summer thunderstorms. Here, and in other semiarid and arid regions, channel recovery after a flood may take several decades. As a result, flood history strongly influences spatial and temporal variability in bottomland vegetation. Interpretation of these patterns must be based on understanding the long—term response of bottomland morphology and vegetation to specific floods. A major flood in 1965 on Plum Creek, a perennial sandbed stream, removed most of the bottomland vegetation and transformed the single—thread stream into a wider, braided channel. Channel narrowing began in 1973 and continues today. In 1991, we determined occurrences of 150 vascular plant species in 341 plots (0.5 m 2 ) along a 7—km reach of Plum Creek near Louviers, Colorado. We related patterns of vegetation to elevation, litter cover, vegetative cover, sediment particle size, shade, and year of formation of the underlying surface (based on age of the excavated root flare of the oldest woody plants). Geomorphic investigation determined that Plum Creek fluvial surfaces sort into five groups by year of formation: terraces of fine sand formed before 1965; terraces of coarse sand deposited by the 1965 flood; stable bars formed by channel narrowing during periods of relatively high bed level (1973—1986); stable bars similarly formed during a recent period of low bed level (1987—1990); and the present channel bed (1991). Canonical correspondence analysis indicates a strong influence of elevation and litter cover, and lesser effects of vegetative cover, shade, and sediment particle size. However, the sum of all canonical eigenvalues explained by these factors is less than that explained by an analysis including only the dummy variables that define the five geomorphically determined age groups. The effect of age group is significant even when all five other environmental variables are specified as covariables. Therefore, the process of postflood channel narrowing has a dominant influence on vegetation pattern. Channel narrowing at Plum Creek includes a successional process: annual and perennial plants become established on the channel bed, sediment accretes around the vegetation, and increasing litter cover, shade, and scarcity of water eliminate species that are not rhizomatous perennials. However, successional trajectories of individual surfaces are modified by flow—related fluctuations of the bed level; surfaces deposited by the 1965 flood have had distinct sediment and vegetation since their formation. Species richness is highest on surfaces dating to 1987—1990; the many species restricted to this transitory assemblage are perpetuated by flood—related fluctuations in channel width. Since the 1965 flood, seedling establishment of the dominant trees (genus Populus) has occurred only on low surfaces formed during channel narrowing. Thus, the flood has indirectly promoted Populus establishment over a 26—yr period.

Ecology↗
USGS1995

Little River revisited - thirty-five years after Hack and Goodlett

In possibly the first detailed study to relate geomorphology, vegetation, and hydrology at a watershed scale, Hack and Goodlett (1960) documented variation in the eastern forest with topograhic positions of cove, side slope, and nose. Runoff identified as convergent, parallel, or divergent, supported forest types, respectively, of northern hardwood, oak, and yellow pine. The study, conducted in the Little River Basin of northwestern Virginia, also described effects on landforms and vegetation of a catastrophic flood that occurred in June, 1949. Field investigations, conducted nearly 4 decades later, review selected parts of the study by Hack and Goodlett (1960). Replicate data provide a basis to evaluate interpretations of Hack and Goodlett, to document geomorphic change within the Little River Basin since the 1949 flood, and to identify vegetation change in uplands and bottomlands. Results suggest that change to hillslope landforms has been minor since 1949, but that changes have occurred to the Little River and its tributaries, seemingly during flow events of 1952, 1955, and 1985. Change in areal extent of forest types was not detected. Change in the relative abundances of dominant species may have resulted from 20th-century fire suppression.

Geomorphology↗
USGS1995

Identifying trends in sediment discharge from alterations in upstream land use

Environmental monitoring is a primary reason for collecting sediment data. One emphasis of this monitoring is identification of trends in suspended sediment discharge. A stochastic equation was used to generate time series of annual suspended sediment discharges using statistics from gaging stations with drainage areas between 1606 and 1 805 230 km2. Annual sediment discharge was increased linearly to yield a given increase at the end of a fixed period and trend statistics were computed for each simulation series using Kendal's tau (at 0.05 significance level). A parameter was calculated from two factors that control trend detection time: (a) the magnitude of change in sediment discharge, and (b) the natural variability of sediment discharge. In this analysis the detection of a trend at most stations is well over 100 years for a 20% increase in sediment discharge. Further research is needed to assess the sensitivity of detecting trends at sediment stations.

Effects of scale on interpretation and management ↗
USGS1994

The healing of disturbed hillslopes by gully gravure

Results of accelerated erosion on certain constructed surfaces in southeastern Arizona appear similar to those described by Bryan (1940) as gully gravure. Twenty cross-section excavations in eight rills incised into silt-rich lacustrine and fluvial deposits reveal partial filling of the rills by debris derived from overlying fluvial sand, gravel, and cobbles. Interstices of the coarse material gradually fill with fine-grained erosion products, decreasing permeability of the fill and deflecting subsequent runoff to the margins of the fill. Rills and rill fillings thus increase in width with time, and complete veneering of the surface by coarse debris ultimately may occur. Through incision, filling, lateral planation, and armoring, channels of the dissected surface heal and the new hillslope approaches an equilibrium condition. Natural hillslopes in the area with similar geologic conditions have inclinations of 16°-22°, have generally unbroken veneers of coarse debris, and appear subject to the same erosional processes identified at constructed hillslopes. Field measurements and the revised universal soil loss equation (RUSLE) were used to estimate soil loss on natural and constructed hillslopes. Results suggest that erosion may be almost three orders of magnitude greater on steep, non-veneered, nonvegetated constructed surfaces than on natural hillslopes. Attributes of stable natural hillslopes provide criteria for the design of stable constructed hillslopes.

Geological Society of America Bulletin↗
USGS1993

Prediction by regression and intrarange data scatter in surface-process studies

Modeling is a major component of contemporary earth science, and regression analysis occupies a central position in the parameterization, calibration, and validation of geomorphic and hydrologic models. Although this methodology can be used in many ways, we are primarily concerned with the prediction of values for one variable from another variable. Examination of the literature reveals considerable inconsistency in the presentation of the results of regression analysis and the occurrence of patterns in the scatter of data points about the regression line. Both circumstances confound utilization and evaluation of the models. Statisticians are well aware of various problems associated with the use of regression analysis and offer improved practices; often, however, their guidelines are not followed. After a review of the aforementioned circumstances and until standard criteria for model evaluation become established, we recommend, as a minimum, inclusion of scatter diagrams, the standard error of the estimate, and sample size in reporting the results of regression analyses for most surface-process studies. ?? 1993 Springer-Verlag.

Environmental Geology↗
USGS1987

Playa-lake basins on the Southern High Plains of Texas and New Mexico: Part II. A hydrologic model and mass-balance arguments for their development.

Hydrologic, geologic, geomorphic, and mass-balance data suggest that most of the ∼30,000 playa lake basins on the Southern High Plains have developed by a combination of dissolution of caliche and piping of surface material into the unsaturated zone rather than by eolian processes as has generally been stated. A conceptual model suggests that particulate organic material, much of which is sorbed on smectite clays, is carried downward from the surface into the unsaturated zone by recharging water. The organic material is oxidized to CO 2 , which dissolves in the water, forms carbonic acid, and dissolves lithologic carbonates. Because organic material is transported and oxidized deep in the unsaturated zone, CO 2 concentrations are much higher at depth than in the soil zone, and recharging water remains thermodynamically subsaturated with respect to carbonates and thus able to dissolve them throughout the unsaturated zone. Dissolution promotes lithologic instability, leading to piping and eluviation of material within the unsaturated zone. Playa basins expand laterally as recharge is concentrated at the edge of the playa floor because of lowered permeability in the center that results from accumulation of clays and other fine sediment. Mass-balance calculations of gas, liquid, and solid fluxes beneath a playa basin suggest that sufficient mass is transported to account for the volume of the depression. Particulate flux is estimated by relating it to the CO 2 flux out of the unsaturated zone. Solute flux is estimated from the difference between input values from the playa lake water and that observed in ground water. Gas flux is measured directly from gas samples at specific depths below the: surface.

Geological Society of America Bulletin↗