Controls on the Spatial Distribution of Trace Metal Concentrations along the Bedrock-Dominated South Fork New River, North Carolina

In marked contrast to alluvial rivers, few studies have examined the physical and geochemical controls on the spatial distribution of toxic trace metals along bedrock channels. This study examined the factors controlling the geographical pattern of selected trace metal (Cu, Cr, and Zn) concentrations along the bedrock-dominated channel of the South Fork New River (SFNR). The SFNR is located in the Blue Ridge Physiographic Province of North Carolina, and is representative of many rivers in mountainous terrains that are often subjected to the influx of toxic trace metals from historic and contemporary mining operations. The topography of the SFNR’s channel bed is highly variable and can be subdivided into pool and shallow bedrock reaches. The latter contained localized cascades characterized by topographically higher bedrock ribs that are separated by topographic lows, both of which are oriented oblique to flow. Accumulations of bed sediments are predominantly associated with the traverse bedrock ribs that generate high hydraulic roughness. Except for a few localized zones of enrichment, sediment-associated trace metal concentrations tended to vary within a narrow range of background values over the 36 km study reach. Elevated trace metal concentrations were closely linked to zones of high Fe and Mn concentrations, and were associated with pools located within or immediately downstream of bedrock cascades. The elevated concentrations of the metals appear to be derived from the erosion of lithologic units within the cascades that contain sulfidic layers or zones of mafic mineral enrichment, and which are known to occur in the underlying bedrock. Once eroded, these minerals and/or rock fragments were deposited within low-velocity zones created by the transverse ribs or within downstream pools. The enrichment of trace metals downstream of the cascades may also be due to the formation of Fe and Mn oxyhydroxides as turbulent flows aerate river waters as they traverse the cascades. Chemically reactive fine-grained (<63 µm) sediments had a relatively limited influence on the downstream variations in metal concentrations, presumably because the channel bed sediments are composed primarily of sand-sized and larger particles. Although a principal component analysis (PCA) suggested that reach-scale variations in channel and valley morphology may have partly influenced downstream variations in trace metal concentrations, the geographical patterns were primarily controlled by local geological and geomorphic factors associated with the bedrock cascades. The design of future sampling programs along such coarse-grained, bedrock rivers should consider the significance of these local controls on trace metal storage to effectively characterize and interpret downstream patterns in metal concentrations.

Effects of Streamside Buffers on Stream Temperatures Associated With Forest Management and Harvesting Using DHSVM-RBM; South Fork Caspar Creek, California

Forest harvesting has been shown to effect water quantity and water quality parameters, highlighting the need for comprehensive forest practice rules. Being able to understand and predict these impacts on stream temperature is especially critical where federally threatened or endangered fish species are located. The goal of this research was to predict responses in stream temperature to potential riparian and forest harvest treatments in a maritime, mountainous environment. The Distributed Hydrology Soil Vegetation Model (DHSVM) and River Basin Model (RBM) were calibrated to measured streamflow and stream temperatures in the South Fork of the Caspar Creek Experimental Watersheds during critical summer periods when temperatures are highest and flows are low for hydrologic years 2010–2016. The modeling scenarios evaluated were (1) varying percentages of stream buffer canopy cover, (2) a harvest plan involving incrementally reduced stand densities in gauged sub-watersheds, and (3) an experimental design converting dominant riparian vegetation along set reaches. The model predicted a noticeable rise in stream temperatures beginning when stream buffer canopy cover was reduced to 25 and 0% retention levels. Larger increases in Maximum Weekly Maximum Temperatures (MWMT), compared to Maximum Weekly Average Temperatures (MWAT), occurred across all scenarios. There was essentially no difference in MWAT or MWMT between altering buffers along only fish bearing (Class I) watercourses and altering buffers along all watercourses. For the scenario with stream buffers at 0% retention, MWMTs consistently rose above recommended thermal limits for coho salmon (Oncorhynchus kisutch). Predictions when clearcutting the entire watershed showed less of an effect than simulations with 0% buffer retention, suggesting groundwater inflows mitigate stream temperature rises in the South Fork. The harvest simulation showed a small but consistent increase in MWATs (avg. 0.11°C), and more varied increases in MWMTs (avg. 0.32°C). Sensitivity analyses suggest potentially unrealistic tracking of downstream temperatures, making the vegetation conversion simulations inconclusive. Additional sensitivity analyses suggest tree height and monthly extinction coefficient (a function of leaf area index) were most influential on temperatures in the South Fork, which was consistent with other modeling studies suggesting management focus on tall, dense buffers compared to wider buffer widths.

PENGUKURAN DEBIT ALIRAN SUNGAI DENGAN MENGGUNAKAN LAJU TERUKUR DAN GEOMETRI ALIRAN

Pengukuran debit laju aliran sungai memiliki peran yang penting misalnya sebagai data ketersediaan pasokan air untuk minum dan irigasi, perhitungan total beban harian maksimum untuk pembuangan bahan kimia, dan energi yang tersedia untuk pembangkit listrik tenaga air. Salah satu metode untuk mengukur deras aliran sungai adalah dengan menggunakan profil kedalaman dan kecepatan deras aliran untuk menghitung aliran rata-rata melalui beberapa bagian dan kemudian menjumlahkannya di bagian-bagian tersebut. Untuk menguji pendekatan ini, pengukuran dilakukan di Sungai South Fork Palouse di Pullman, WA, Amerika Serikat di dua lokasi pengukuran dan pada dua hari yang berbeda. Hasil penelitian menunjukkan bahwa rata-rata laju aliran yang diukur pada dua lokasi pada hari pertama adalah 3,2 dan 3,0 ft kubik per detik (cfs) dan pada hari kedua adalah 2,8 dan 2,88 cfs. Laju aliran ini sedikit lebih rendah dari laju aliran resmi yang diukur oleh USGS (kesalahan antara 7% hingga 11%). Namun perbedaan ini dapat dijelaskan dengan adanya faktor kontribusi anak sungai . Secara statistik, tidak ada perbedaan antara pasangan lokasi dan hari yang signifikan secara statistik pada α = 0,05, namun, tampaknya aliran lebih mirip antara dua lokasi pada hari yang sama dibandingkan antara dua hari di lokasi yang sama. Tingkat kesalahan dan variabilitas cukup rendah sehingga metode penghitungan aliran sungai ini kemungkinan besar akan cukup akurat untuk sebagian besar aplikasi dan paling dapat diterapkan di tempat-tempat di mana pengambilan data aliran sungai jarang dilakukan. Kata Kunci: debit aliran sungai, Pullman, kecepatan terukur, geometri aliran

Topographic Thresholds and Soil Preservation along the Southern High Plains Eastern Escarpment, Northwest Texas, USA

The eastern escarpment of the Southern High Plains (USA) is today a semi-arid erosional landscape delineated by canyon breaks and topographic relief. A series of buried soils were identified, described, and sampled at 19 soil profile localities exposed along terraces of the South Fork of the Double Mountain Fork of the Brazos River (South Fork) and two associated tributaries (Spring Creek and Macy 285 drainage). Radiocarbon dating revealed late-Pleistocene to early Holocene (~12,580–9100 14C B.P.), middle-Holocene (~6025–4600 14C B.P.), and late-Holocene (~2000–800 14C B.P.) buried soils. The late-Pleistocene to middle-Holocene soils were preserved only at higher elevations within the upper section of the South Fork and Spring Creek. A topographic position analysis was conducted using GIS to identify and examine the impacts of a soil topographic threshold on the preservation and distribution of buried soils within this geomorphic system. Above the identified ~810 m threshold, lateral migration of channels was constrained. Extensive channel migration below the threshold removed older terraces that were replaced with late-Holocene terraces and associated buried soils. Landscape topography constraints on geomorphic processes and soil formation impacted the preservation of archaeological sites in this semi-arid region.

Metamorphic Temperatures and Pressures across the Eastern Franciscan: Implications for Underplating and Exhumation

The Eastern Belt of the Franciscan Complex in the northern California Coast Ranges consists of coherent thrust sheets predominately made up of ocean floor sediments subducted in the Early Cretaceous and then accreted to the overriding plate at depths of 25-40 km. Progressive packet accretion resulted in the juxtaposition of a series of thrust sheets of differing metamorphic grades. This study utilizes laser Raman analysis of carbonaceous material to determine peak metamorphic temperatures across the Eastern Belt and phengite barometry to determine peak metamorphic pressures. Locating faults that separate packets in the field is difficult, but they can be accurately located based on differences in peak metamorphic temperature revealed by Raman analysis. The Taliaferro Metamorphic Complex in the west reached 323-336°C at a minimum pressure of ~11 kbar; the surrounding Yolla Bolly Unit 215–290°C; the Valentine Springs Unit 282-288°C at 7.8±0.7 kbar; the South Fork Mountain Schist 314–349°C at 8.6–9.5 kbar, a thin slice in the eastern portion of the SFMS, identified here for the first time, was metamorphosed at ~365°C and 9.7±0.7 kbar; and a slice attributed to the Galice Formation of the Western Klamath Mountains at 281±13°C. Temperatures in the Yolla Bolly Unit and Galice slice were too low for the application of phengite barometry. Microfossil fragments in the South Fork Mountain Schist are smaller and less abundant than in the underlying Valentine Springs Unit, providing an additional method of identifying the boundary between the two units. Faults that record a temperature difference across them were active after peak metamorphism while faults that do not were active prior to peak metamorphism, allowing for the location of packet bounding faults at the time of accretion. The South Fork Mountain Schist consists of two accreted packets with thicknesses of 300 m and 3.5 km. The existence of imbricate thrust faults both with and without differences in peak metamorphic temperature across them provides evidence for synconvergent exhumation.

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

The South Fork of Wright Valley contains one of the largest rock glaciers in the McMurdo Dry Valleys, Antarctica, stretching 7 km from the eastern boundary of the Labyrinth and terminating at Don Juan Pond (DJP). Here, we use results from ground-penetrating radar (GPR), qualitative field observations, soil leaching analyses and X-ray diffraction analyses to investigate rock glacier development. The absence of significant clean ice in GPR data, paired with observations of talus and interstitial ice influx from the valley walls, support rock glacier formation via talus accumulation. A quartz-dominated subsurface composition and discontinuous, well-developed desert pavements suggest initial rock glacier formation occurred before the late Quaternary. Major ion data from soil leaching analyses show higher salt concentrations in the rock glacier and talus samples that are close to hypersaline DJP. These observations suggest that DJP acts as a local salt source to the rock glacier, as well as the surrounding talus slopes that host water track systems that deliver solutes back into the lake, suggesting a local feedback system. Finally, the lack of lacustrine sedimentation on the rock glacier is inconsistent with the advance of a glacially dammed lake into South Fork during the Last Glacial Maximum.

Archeological Investigations in the Upper Trinity River Basin in Parker County, Texas

Homer Norris (1929-2018), a commercial artist by profession and a life-time resident of eastern Parker County, in North-Central Texas, in the South Fork and Clear Fork drainages of the upper Trinity River basin, roamed the landscape from at least 30-50 years ago in search of archeological evidence of Native American use and settlement in the basin. He took and maintained detailed notes, records, and drawings of the sites he found and the artifacts he recovered, as well as pertinent information on the context of finds, including those noted eroding out of stream cut banks and in stream beds of the South Fork and Clear Fork in the Anetta-Aledo areas of Parker County, about 15 miles west of Fort Worth, an area of about 5 miles on a side. This information, made available by his daughter Lanie Garmon of Aledo, Texas, from his archeological investigations is detailed herein, along with a summary of how his investigations contribute to a fuller understanding of the native history of this region of Texas.