Filters: Tags: Geomorphology (X) > Categories: Publication (X)
48 results (80ms)
Filters
Date Range
Extensions Types Contacts
Categories Tag Types Tag Schemes |
The combined influence of tree-clearing, road construction, snowmaking, and machine-grading can cause increased flow and sediment loads along streams in or adjacent to commercial ski resorts. These changes to stream channels can increase bank failures, bed material size, pool scour, and, in extreme cases, channel incision. We used field data from the White River National Forest in Colorado, which includes several major ski resorts, to test the hypothesis that ski slope development causes a significant difference in bank stability, undercut banks, fine sediment, wood load, pool residual depth, and particle size (D84) between the ski area project streams and reference streams. We further hypothesize that the changes...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Colorado,
Geomorphology,
bank erosion,
channel change,
commercial ski resorts,
The benefits of gradually removing a dam (through multiple notches) are to reduce the total project cost and reduce possible environmental effects by allowing the impounded sediment to slowly move downstream, and a stable stream and revegetated floodplain to form upstream. Notching, in this study of a dam on Brewster Creek, near St. Charles, Illinois, involves cutting a given height (in five 12–18 inch notches over approximately a 9 month period) across the length (or some portion of the length) of the dam. Brewster Creek is a tributary of the Fox River in northeastern, Illinois. Sediment, dissolved oxygen, and geomorphic response are being monitored before, during, and after a gradual (notching) removal of the...
Categories: Publication;
Types: Citation;
Tags: Analysis,
Automated sampling,
Calculation,
Costs,
Costs analysis,
Landforms along the Pacific, Gulf of Mexico, and Atlantic coastlines for the conterminous United States are attributed with the relative vulnerability of horizontal erosion due to sea-level rise to characterize coastal zone stability. The position and extent of landforms are geospatially indexed as line-events where these coastal zone features are intersected by the linear-referenced 2013 - 2014 U.S. Geological Survey National Hydrography Dataset Coastline, which corresponds to the National Oceanic and Atmospheric Administration (NOAA) 2013 - 2014 mean high water level datum delineated in intertidal zones open to oceans, behind barrier coasts in bays, lagoons, and estuaries, and sometimes where tidal currents reach...
Categories: Data,
Data Release - In Progress,
Publication;
Types: ArcGIS REST Map Service,
ArcGIS Service Definition,
Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: Geomorphology,
Gulf,
Gulf of Mexico,
HEM,
Hydro linked data,
The relationship between form and function has been a central organizing principle in biology throughout its history as a formal science. This concept has been relevant from molecules to organisms but loses meaning at population and community levels where study targets are abstract collectives and assemblages. Ecosystems include organisms and abiotic factors but ecosystem ecology too has developed until recently without a strong spatially explicit reference. Landscape ecology provides an opportunity to once again anneal form and function and to consider reciprocal causation between them. This ecomorphologic view can be applied at a variety of ecologically relevant scales and consists of an investigation of how geomorphology...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Geomorphology,
ecomorphology,
ecosystem,
feedback,
geomorphology,
A regional synthesis of paleoflood chronologies on rivers in Arizona and southern Utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations. The flood chronologies were constructed using fine-grained slackwater deposits that accumulate in protected areas along the margins of bedrock canyons and selectively preserve evidence of the largest events. High-magnitude floods were frequent on rivers throughout the region from 5000 to 360014C yrs BP (dendrocalibrated age = 3800-2200 BC) and increased again after 2200 BP (400 BC), with particularly prominent peaks in magnitude and frequency around 1100-900 BP (AD 900?1100)...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Arizona,
Geomorphology,
Holocene climate,
Utah,
fluvial geomorphology,
Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200?1400 and 1860?1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base of...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: El Nino,
Geological Society of America Bulletin,
Holocene,
alluvial deposits,
arroyos,
Even in heavily engineered river systems, climate still governs flood variability and thus still drives many levee breaks and geomorphic changes. We assemble a 155-year record of levee breaks for a major California river system to find that breaks occurred in 25% of years during the 20th Century. A relation between levee breaks and river discharge is present that sets a discharge threshold above which most levee breaks occurred. That threshold corresponds to small floods with recurrence intervals of ∼2–3 years. Statistical analysis illustrates that levee breaks and peak discharges cycle (broadly) on a 12–15 year time scale, in time with warm-wet storm patterns in California, but more slowly or more quickly than...
Landforms along the Pacific, Gulf of Mexico, and Atlantic coastlines for the conterminous United States are attributed with the relative vulnerability of horizontal erosion due to sea-level rise to characterize coastal zone stability. The position and extent of landforms are geospatially indexed as line-events where these coastal zone features are intersected by the linear-referenced 2013 - 2014 U.S. Geological Survey National Hydrography Dataset Coastline, which corresponds to the National Oceanic and Atmospheric Administration (NOAA) 2013 - 2014 mean high water level datum delineated in intertidal zones open to oceans, behind barrier coasts in bays, lagoons, and estuaries, and sometimes where tidal currents reach...
Categories: Data,
Data Release - In Progress,
Publication;
Types: ArcGIS REST Map Service,
ArcGIS Service Definition,
Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: Atlantic,
Connecticut,
Delaware,
Florida,
Geomorphology,
The salt valleys over the axis of the salt-cored anticlines in the Paradox fold and fault belt (Canyonlands, Utah and Colorado) are created by subsidence of the anticline crests. Traditionally, the collapse of the anticlinal crests was attributed to dissolution of the salt walls (diapirs) forming the anticline cores. Recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions. This paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation. The development of...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Colorado Plateau,
Geomorphology,
Paradox Basin,
dissolution subsidence,
evaporite karst,
The salt valleys over the axis of the salt-cored anticlines in the Paradox fold and fault belt (Canyonlands, Utah and Colorado) are created by subsidence of the anticline crests. Traditionally, the collapse of the anticlinal crests was attributed to dissolution of the salt walls (diapirs) forming the anticline cores. Recent studies based on scaled physical models and field observations propose that the salt valleys are a result of regional extension and that salt dissolution had only a minor influence in the development of the axial depressions. This paper presents several arguments and lines of evidence that refute the tectonic model and support the salt dissolution subsidence interpretation. The development of...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Colorado Plateau,
Geomorphology,
Paradox Basin,
dissolution subsidence,
evaporite karst,
Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200–1400 and 1860–1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: El Nino,
Geological Society of America Bulletin,
Holocene,
alluvial deposits,
arroyos,
Closure of Glen Canyon Dam in 1963 transformed the Colorado River by reducing the magnitude and duration of spring floods, increasing the magnitude of base flows, and trapping fine sediment delivered from the upper watershed. These changes caused the channel downstream in Glen Canyon to incise, armor, and narrow. This study synthesizes over 45 yr of channel-change measurements and demonstrates that the rate and style of channel adjustment are directly related to both natural processes associated with sediment deficit and human decisions about dam operations. Although bed lowering in lower Glen Canyon began when the first cofferdam was installed in 1959, most incision occurred in 1965 in conjunction with 14 pulsed...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Geological Society of America Bulletin,
alluvial deposits,
channel adjustment,
dams,
erosion,
Alluvial reaches of the Colorado River near Grand Junction, Colorado, provide important habitat for the endangered Colorado squawfish (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus). Populations of these native fishes have declined dramatically in the past several decades, a situation that is often attributed to the hydrological and ecological effects of upstream reservoir operations. This report summarizes research done over the last five years to evaluate the importance of historical changes in streamflow and sediment loads on alluvial reaches of the Colorado River near Grand Junction. In addition, we describe recent changes in the geomorphology of the Colorado River and address the question of...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Average Boundary Shear Stress,
Dimensionless Shear Stress,
backwaters,
bed load sediment,
effective discharge,
Dr. Richard Janda of the USGS began a channel monitoring program in Redwood Creek in northern coastal California in 1973. The USGS continued this work through 2013, when the Research Geologist, Dr. Mary Madej retired. This effort produced 40 years of channel change data in rivers that were disrupted by severe erosion following timber harvest of old-growth redwood forests, a portion of the program's data (plus 1953 data) has been preserved in this data release. Original field surveys documented bank erosion, aggradation, and degradation at 60 cross-sectional transects at annual or biannual timesteps. Three river reaches also have long-term longitudinal channel bed surveys which document the distribution and development...
Categories: Data,
Publication;
Types: Citation,
Downloadable,
Map Service,
OGC WFS Layer,
OGC WMS Layer,
Shapefile;
Tags: 44 Creek,
Bond Creek,
California,
Dolason Creek,
Elam Creek,
A field study was conducted to ascertain the amount of protection that mesquite-dominated communities provide to the surface from wind erosion. The dynamics of the locally accelerated evolution of a mesquite/coppice dune landscape and the undetermined spatial dependence of potential erosion by wind from a shear stress partition model were investigated. Sediment transport and dust emission processes are governed by the amount of protection that can be provided by roughness elements. Although shear stress partition models exist that can describe this, their accuracy has only been tested against a limited dataset because instrumentation has previously been unable to provide the necessary measurements. This study combines...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Geomorphology,
atmospheric boundary layer,
drag partition,
field study,
shear stress partitioning,
Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200?1400 and 1860?1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base of...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: El Nino,
Geological Society of America Bulletin,
Holocene,
alluvial deposits,
arroyos,
As in many areas of high relief, debris flows are an important process linkage between hillslopes and the Green River in the canyons of the eastern Uinta Mountains, yet the physical conditions that lead to debris flow initiation are unknown. A recent episode of enhanced debris-flow and wildfire activity provided an opportunity to examine the geomorphic impact of fire and the processes by which weathered bedrock is transported to the Green River. Field investigations and analysis of elevation and precipitation data were undertaken in 15 catchments with recent debris flows to determine how surficial geology, wildfire, topography, bedrock strength, and meteorology influence hillslope processes. The recent debris flows...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Geomorphology,
Green River,
bedrock,
debris flow,
eastern Uinta Mountains,
Land use practices in Colorado during the last two centuries altered the supply of sediment and water to many channels in the upper South Platte Basin. As a result of increased supply of sediment and mobility and reduced peak flows, the characteristics of pools associated with channel constrictions, referred to as forced pools, may have been altered. Increased supply of sediment and reduced transport capacity of high flows could lead to aggradation in forced pools. Channel confined by road corridors could lead to high velocities at normal flows, increased energy dissipation from riprap, or even increased pool frequency resulting from failed riprap. To assess potential alterations, four hypotheses were tested: (1)...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Bankfull pool spacing,
Colorado Front Range,
Forced pools,
Geomorphology,
Land use effects,
Land degradation in drylands is one of the major environmental issues of the 21st century particularly due to its impact on world food security and environmental quality. Climate change, shifts in vegetation composition, accelerated soil erosion processes, and disturbances have rendered these landscapes susceptible to rapid degradation that has important feedbacks on regional climate and desertification. Even though the role of hydrologic–aeolian erosion and vegetation dynamic processes in accelerating land degradation is well recognized, most studies have concentrated only on the role of one or two of these components, and not on the interactions among all three. Drawing on relevant published studies, here we...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Drylands,
Ecogeomorphology,
Geomorphology,
Land degradation,
Sediment transport,
This study examines bed and bank adjustment in the 105-km reach of the Green River immediately downstream from Flaming Gorge Dam by the use of historical aerial and oblique photographs, analysis of current and abandoned stream-gaging records, and field observations. Although this segment has been previously characterized as sediment deficient, these data show that sediment is accumulating in all reaches and that the bed has not degraded at any location where historical data are available. Adjustment is occurring through a combination of deposition of post-dam sediment and stabilization of pre-dam deposits, resulting in a 10?30% reduction in average width of the channel. All post-dam surfaces are colonized by woody...
Categories: Publication;
Types: Citation,
Journal Citation;
Tags: Geomorphology,
channel adjustment,
channel narrowing,
dams,
degradation,
|
|