نتایج جستجو برای: Alluvial

تعداد نتایج: 3577  

Journal: :Proceedings of the National Academy of Sciences of the United States of America 2000
W J Trush S M McBain L B Leopold

Rivers around the world are being regulated by dams to accommodate the needs of a rapidly growing global population. These regulatory efforts usually oppose the natural tendency of rivers to flood, move sediment, and migrate. Although an economic benefit, river regulation has come at unforeseen and unevaluated cumulative ecological costs. Historic and contemporary approaches to remedy environme...

2004
Demetre P. Argialas Angelos Tzotsos

There is a need to automate terrain feature mapping so that to make the process more objective and less time consuming by using proper feature extraction techniques. The objective of this study was the use of object-oriented image analysis methods for the automatic extraction of alluvial fan terrain units. The study area was located in the Death Valley, Nevada, USA. The data used included an AS...

2016
Daniel Hunkeler

Alluvial aquifers in mountainous regions cover typically a limited area. Their contribution to catchment storage and outflow is rarely isolated; alluvial groundwater discharge under gauging stations is generally assumed negligible; and hydrological models tend to lump alluvial storage with other units. The role of alluvial aquifers remains therefore unclear: can they contribute significantly to...

2001
G. A. Smith

Alluvial slopes are piedmonts characterized by parallel steam channels rather than alluvial fans. They are common landforms in extensional basins of the south-western United States but have received little attention from geomorphologists or sedimentologists. Persistence of channellized flow across piedmonts, as opposed to sheetflooding due to loss of flow confinement on alluvialfan surfaces, di...

Journal: :تحقیقات جغرافیایی 0
علیرضا تقیان دانشگاه اصفهان

abstract alluvial fans are the most striking phenomena o fluvial geomorphology . these forms are found in frount of mountains and pediments of arid and semiarid zones . alluvial fans are affected by climate changes and tectonics . occurring of tectonic events lead to reaction of alluvial fans . some of these reactions appear on dissection of alluvial fans and displacement of depocenters on allu...

2007
A. M. HARVEY

This volume presents a series of papers on the geomorphology, sedimentology and dynamics of alluvial fans, selected from those presented at the 'Alluvial Fans' Conference held in Sorbas, SE Spain in June 2003. The conference was sponsored primarily by the British Geomorphological Research Group and the British Sedimentological Research Group, both organizations affiliated to the Geological Soci...

2005
Jeffrey M. Moore Alan D. Howard

[1] Several dozen distinct alluvial fans, 10 to 40 km long downslope, have been observed in highlands craters. Within a search region between 0 and 30 S, alluvial fan-containing craters were found only between 18 and 29 S, and they all occur at around ±1 km of the MOLA-defined Martian datum. Within the study area they are not randomly distributed but instead form three distinct clusters. Fans t...

2013
Vicente M. Ortuño José D. Gilgado Alberto Jiménez-Valverde Alberto Sendra Gonzalo Pérez-Suárez Juan J. Herrero-Borgoñón

In this paper we describe a new type of subterranean habitat associated with dry watercourses in the Eastern Iberian Peninsula, the "Alluvial Mesovoid Shallow Substratum" (alluvial MSS). Historical observations and data from field sampling specially designed to study MSS fauna in the streambeds of temporary watercourses support the description of this new habitat. To conduct the sampling, 16 su...

2012
PETER C. PATTON

Harris Wash, a tributary of the Escalante River in south-central Utah, has two wellpreserved alluvial terraces of compound origin in its lower reaches. The alluvial stratigraphy of the deposits that compose these terraces reflects the complex processes of canyon filling and erosion. The compound terraces were formed by general aggradation of the valley, by deposition from large floods that also...

2015
Enrica Viparelli Jeffrey A. Nittrouer Gary Parker

The lowermost Mississippi River, defined herein as the river segment downstream of the Old River Control Structure and hydrodynamically influenced by the Gulf of Mexico, extends for approximately 500 km. This segment includes a bedrock (or more precisely, mixed bedrock-alluvial) reach that is bounded by an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition. Here w...

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