Interaction of two tributary glacier branches and implications for surge behavior

Thesis (M.S.) University of Alaska Fairbanks, 2018A glacier surge is a dynamic phenomenon where the glacier after a long period of quiescence, increases its velocities by up to two orders of magnitude. These surges tend to have complex interactions with tributaries, yet the role of these tributary interactions towards glacier surging has yet to be fully investigated. In this work we construct a synthetic glacier with an adjustable tributary intersection angle to study tributary interaction with the trunk glacier. The geometry we choose is loosely based on the main trunk and tributary interaction of Black Rapids Glacier, AK, USA, which last surged in 1936-1937. We investigate surface elevations, medial moraine locations, and erosive power at the bed of the glacier in response to our adjustable domain and relative flux. A nonlinear relationship between tributary flux and surface elevations is found that indicates flow restrictions can occur with geometries like Black Rapids Glacier. These flow restrictions cause increased ice thicknesses up-glacier which can lead to surges via increased stresses

Influence of junction angle on three-dimensional flow structure and bed morphology at confluent meander bends during different hydrological conditions

© 2014 John Wiley & Sons, Ltd. Recent field and modeling investigations have examined the fluvial dynamics of confluent meander bends where a straight tributary channel enters a meandering river at the apex of a bend with a 90° junction angle. Past work on confluences with asymmetrical and symmetrical planforms has shown that the angle of tributary entry has a strong influence on mutual deflection of confluent flows and the spatial extent of confluence hydrodynamic and morphodynamic features. This paper examines three-dimensional flow structure and bed morphology for incoming flows with high and low momentum-flux ratios at two large, natural confluent meander bends that have different tributary entry angles. At the high-angle (90°) confluent meander bend, mutual deflection of converging flows abruptly turns fluid from the lateral tributary into the downstream channel and flow in the main river is deflected away from the outer bank of the bend by a bar that extends downstream of the junction corner along the inner bank of the tributary. Two counter-rotating helical cells inherited from upstream flow curvature flank the mixing interface, which overlies a central pool. A large influx of sediment to the confluence from a meander cutoff immediately upstream has produced substantial morphologic change during large, tributary-dominant discharge events, resulting in displacement of the pool inward and substantial erosion of the point bar in the main channel. In contrast, flow deflection is less pronounced at the low-angle (36°) confluent meander bend, where the converging flows are nearly parallel to one another upon entering the confluence. A large helical cell imparted from upstream flow curvature in the main river occupies most of the downstream channel for prevailing low momentum-flux ratio conditions and a weak counter-rotating cell forms during infrequent tributary-dominant flow events. Bed morphology remains relatively stable and does not exhibit extensive scour that often occurs at confluences with concordant beds

Analysis of New Artifact Collections from Archaic to Ancestral Caddo Sites in the Saline Creek Basin in Northern Smith County, Texas

This article concerns the continued documentation of prehistoric and/or historic artifacts from four sites in the Saline Creek drainage basin in the Post Oak Savannah in northern Smith County, Texas. Perttula and Walters discussed an earlier analysis of a set of collections from these same sites. Saline Creek is a northward-flowing tributary to the Sabine River. The sites are ca. 10 km south of the confluence of Saline Creek with the Sabine River. Saline Creek enters into the Sabine River about 6 km east (downstream) of the confluence of another major tributary, Lake Fork Creek, with the river

Tributary Glacier Surges: An Exceptional Concentration at Panmah Glacier, Karakoram Himalaya

Four tributaries of Panmah Glacier have surged in less than a decade, three in quick succession between 2001 and 2005. Since 1985, 13 surges have been recorded in the Karakoram Himalaya, more than in any comparable period since the 1850s. Ten were tributary surges. In these ten a full run-out of surge ice is prevented, but extended post-surge episodes affect the tributary and main glacier. The sudden concentration of events at Panmah Glacier is without precedent and at odds with known surge intervals for the glaciers. Interpretations must consider the response of thermally complex glaciers, at exceptionally high altitudes and of high relief, to changes in a distinctive regional climate. It is suggested that high-altitude warming affecting snow and glacier thermal regimes, or bringing intense, short-term melting episodes, may be more significant than mass-balance change

Mobility in a Wyoming Population of Speyeria Atlantis as Determined by Tagging (Lepidoptera: Nymphalidae)

Excerpt: In my study of Speyeria distribution (Moeck, 1957; Grey & Moeck, 1962; Grey, Moeck & Evans, 1963) it was found desirable to determine the degree of mobility of the individuals in a population of Speyeria atlantis (Edwards). For this study I selected an isolated population of atlantis along a tributary of Horse Creek on the eastern slope of the South Laramie Range, some 17 or 18 miles northwest of Laramie. The specimens along this tributary were dark and well silvered, closely approaching the typical appalachian form in the Black Hills. This colony, furthermore, was the only population of atlantis found in about four parallel tributaries of Horse Creek. By the term appalachian Grey and I refer to the parent stock of the species, ranging in the East from the Maritime Provinces to West Virginia and westward toward the Great Lakes

Propagation and deposition of stony debris flows at channel confluences

The fluid dynamics of stony debris flows generated in two small tributaries adjacent to each other and flowing into a main receiving channel was analyzed experimentally at a laboratory scale. The analysis on the propagation along the tributaries and deposition in the main channel provide information about sediment-water mobility, dangerous damming, and potential hazard. Debris flows were generated by releasing a preset water discharge over an erodible layer of saturated gravels material. As a consequence, the debris flow sediment concentration varied accordingly to the entrainment rate which, in turn, was strongly controlled by the tributary slope. The data collected by acoustic level sensors, pore fluid pressure transducers, and a load cell were used to characterize the evolution of bulk density and solid concentration of the sediment-water mixture. These two parameters were relevant to assess the stony debris flow mobility which contributes to determine the shape of sediment deposits in the main channel. The detailed bed topography surveys carried out in the main channel at the end of each experiment provided information on the morphology of these deposits and on the interplay of adjacent confluences. The influences of conflu- ence angle, tributary slopes, and triggering conditions have been investigated, for a total of 18 different configurations. Within the investigated range of parameters, the slope angle was the parameter that mainly influences the stony debris flow mobility while, for adjacent confluences, the degree of obstruction within the receiving channel was strongly influenced by the triggering scenario

A mineral reconnaissance survey of the Abington-Biggar-Moffat-area, south-central Scotland

Panned heavy mineral concentrates, mostly obtained from stream sediments, were collected from 195 sites in the Abington-Biggar-Moffat area. The project area, which lies immediately east of the formerly important mining district of Wanlockhead-Leadhills, covers approximately 500 km2 of the north-central sector of the Southern Uplands. It incorporates the Hart Fell range of hills, the headwaters catchment for the River Tweed and River Annan, some tributaries of the River Clyde, and, to the east, the Culter Water, Talla Reservoir, Megget Water and the head of the Ettrick valley. Numerous new occurrences of lead, zinc, copper and barium minerals were found and nine areas are recommended for further investigation. Minor amounts of baryte and traces of cupriferous pyrite were identified in the basal breccia of the-New Red Sandstone deposits in Annandale. The mercury mineral, cinnabar, was identified for the first time in Scotland, occurring in trace amounts in stream sediment concentrates in the Coulter area close to the Southern Upland Fault. Chromiferous spine1 was recognised as a major constituent in the majority of panned samples. It is present as a detrital mineral in greywackes but must have been originally derived from ultrabasic rocks. An unusual mineral widely dispersed in trace amounts is corundum (including some gem-quality sapphire). Historical references (Lauder Lindsay, 1868-9, 1871) to a wide distribution for particle gold were confirmed and many new occurrences found. A local provenance for the element is now considered certain. Some placer concentration of gold and chromiferous spine1 is likely in the alluvium of the valleys of the River Tweed and the Megget Water. Six greywacke formations, previously defined in other parts of the Southern Uplands, were mapped in the project area, each distinguished by a characteristic lithology and heavy mineral content

Toward systematical understanding of “Tributary system” in the Ming dynasty:

In arguing about the theoretical framework of the Chinese “tributary system”, itsSino-centric basis and its function as an expedient for trade have often been mixed up.To clear up this confusion, it would be helpful to reexamine its function andtransformation from the perspective that the tributary system was built up through anaccumulation of activities related with paying a tribute. In this paper, I firstly examinepreviously published tables of tributary cases in the Ming dynasty, and confirm theimportance of traffic of envoys with tributary activities. Secondly I present a table oftributary cases in twenty-three years and eight months of the reign of EmperorXianzong, based on Ming shilu (the Veritable Records of the Ming Dynasty), then bringup dimensions of tributary activities in the Ming dynasty and future subjects to construct the tables of tributary cases