نتایج جستجو برای: layered gravel
تعداد نتایج: 37400 فیلتر نتایج به سال:
Deposits of open-framework gravel occurring in gravelly streambeds can exert a significant influence on hyporheic flow. The influence was quantified using a numerical model of the hyporheic zone. The model included open-framework gravel stratasets represented with commonly observed characteristics including a volume fraction of about one-third of the streambed sediment, a hydraulic conductivity...
Natural gravel bed channels commonly contain a fine mode of sand and fine gravel that fills voids of the bed framework of coarser gravel. If the supply of fine bed material exceeds the storage capacity of framework voids, excess fine material forms surficial patches, which can be voluminous in pools during low flow. Data collected in 34 natural channels in northern California and southern Orego...
Field investigations at Dugway Proving Ground in western Utah have produced new data on the chronology and human occupation of late Pleistocene and early Holocene lakes, rivers, and wetlands in the Lake Bonneville basin. We have classified paleo-river channels of these ages as “gravel channels” and “sand channels.” Gravel channels are straight to curved, digitate, and have abrupt bulbous ends. ...
10 Domestic wells in North America and elsewhere are typically constructed at relatively shallow 11 depths and with the sand or gravel pack extending far above the intake screen of the well (shallow 12 well seal). The source areas of these domestic wells and the effect of an extended gravel pack on the 13 source area are typically unknown and few resources exist for estimating these. In this pa...
How the captive environment influences the behavior of animals is relevant to the well-being of captive animals. Captivity diverges from the natural environment in many ways, and one goal of enrichment practices is to encourage species-typical behavior in these unnatural environments. This study investigated the influence of grass vs. gravel substrate on activity budgets and degree of hair loss...
Radiocarbon dating of a wood sample from the upper part of a sequence of coarse fluvial gravels at Branchs Creek has confirmed that accumulation of coarse fluvial gravels continued into the late Mid Holocene, prior to an influx of up to 3 m of sand during the last two millenia. Ongoing erosion at Branchs Creek has revealed that clay previously interpreted as a separate unit beneath the gravels ...
Airborne Laser Scanning or LiDAR data are widely used nowadays in river valleys for topography and hydro-morphology. However, the large data sets of unprocessed 3D point clouds require some challenging treatment and end-users may prefer to deal with DTMs (Digital Terrain Models) derived from LiDAR surveys. Without any complementary data (such as field survey or photographs) detecting position a...
In many gravel-bedded rivers, floods that fill the channel banks create just enough shear stress to move the median-sized gravel particles on the bed surface (D50). Because this observation is common and is supported by theory, the coincidence of bankfull flow and the incipient motion of D50 has become a commonly used assumption. However, not all natural gravel channels actually conform to this...
Coarse-grained beaches are particularly prevalent in the UK, composed of accumulations of either gravel, or mixed sand and gravel sediments. Understanding and predicting their morphological behaviour in response to short-term and long-term forcing has been the subject of recent research. Despite the focus on sandy beaches, it is important to understand that the balance of processes that govern ...
—Endangered Interior Least Terns ( Sterna antillarum athalassos ) and threatened Piping Plovers ( Charadrius melodus ) nest in Nebraska at gravel mines where they are vulnerable to disturbance and nest loss. Conflicts occur when their nesting and protected status delay mining activities. The possibility of shifting nesting from active to inactive mining areas by using a deterrent (mylar flaggin...
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