Alluvial fans of the Eastern Italian Alps: morphometry and depositional processes

1995 ◽  
Vol 8 (1) ◽  
pp. 20-27 ◽  
Author(s):  
L. Marchi ◽  
P.R. Tecca
1993 ◽  
Vol 37 (4) ◽  
pp. 447-458
Author(s):  
Lorenzo Marchi ◽  
Alessandro Pausto ◽  
Pia R. Tecca

2016 ◽  
Vol 47 (1) ◽  
pp. 344 ◽  
Author(s):  
K. Valkanou ◽  
E. Karymbalis ◽  
D. Papanastassiou ◽  
K. Gaki-Papanastassiou ◽  
P. Giles

This paper deals with the morphometric analysis of 42, late Holocene, coastal alluvial fans located along the coasts of the tectonically active North Evoikos Gulf in central Greece. Thirty six of the fans have been formed by streams that discharge along the east coast of the Gulf (Evia Island) while the rest are located on the opposite side (Continental Greece). Selected morphometric parameters of the drainage basins were measured using topographic maps at the scale of 1:50,000 while those of the fans were derived from detailed topographic diagrams at the scale of 1:5,000 utilizing ESRI’s ArcGIS9.3 software. Fans were classified into four groups according to the primary depositional processes (fluvial and/or debris flow). Another classification criterion was the relationship between the location of the fan-catchment system and the local tectonic patterns (active faults). Fan-basin morphometric relationships for each fan group were also investigated. A strong positive relation was found between the size of the fan and the drainage basin area while the correlation between drainage area and fan slope was negative. Large catchments located near fault terminations have formed gently sloping fans dominated by fluvial processes, whereas torrents with small rough drainage basins, developed on the footwall, have formed steep fans likely dominated by debris-flow along the east coast of the Gulf


2017 ◽  
Vol 21 (2) ◽  
pp. 721-733 ◽  
Author(s):  
Lin Zhu ◽  
Huili Gong ◽  
Zhenxue Dai ◽  
Gaoxuan Guo ◽  
Pietro Teatini

Abstract. Alluvial fans are highly heterogeneous in hydraulic properties due to complex depositional processes, which make it difficult to characterize the spatial distribution of the hydraulic conductivity (K). An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional (3-D) setting by using geological and geophysical data. More specifically, a large number of inexpensive vertical electric soundings are integrated with a facies model developed from borehole lithologic data to simulate the log10(K) continuous distributions in multiple-zone heterogeneous alluvial megafans. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multiple-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (zone 1) to the lower (zone 3) portion along the flow direction. In zone 1, sediments were moved by higher-energy flooding, which induces poor sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from zone 1 to zone 3. The results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of K in alluvial fans.


2000 ◽  
Vol 22 ◽  
Author(s):  
F. Maotovani ◽  
A. Pasuto ◽  
S. Silvaoo

The correct interpretation of landslide hazard, and consequently the optimisation of the interventions to be carried out in order to mitigate the loss of human lives and economic assets, depends on some general considerations. Firstly, gravitational phenomena should be regarded as an effect of natural landscape evolution, and secondly, the interaction of these phenomena with human activities and structures causes casualties and damage. Indeed, the population growth has led to greater needs for space and natural resources. On the other hand, the constant technological progress and improvement of living standards have caused remarkable changes in natural environment. Consequently, the events such as landslides have had increasingly serious consequences on human life and activities. The Eastern Italian Alps, and in particular the Dolomites, are famous mountainous areas for their well-organised winter and summer resorts located at different elevations along the slopes and in the valleys.  The territory includes high (more than 3,000 m) peaks alternating with densely populated valleys. Most of the villages are located on alluvial fans, at the bottom of the valley, or on the toe of ancient landslide accumulations. This fact implies a high degree of risk for civil populations, urban settlements, and infrastructure. The Dolomites are prone to sliding owing to their steeps lopes and unfavourable structural setting (i.e. an intensely faulted and jointed sequence of rigid and plastic formations).  In this framework, the paper describes some experience of landslide investigations and monitoring carried out in this area.


2016 ◽  
Author(s):  
Lin Zhu ◽  
Huili Gong ◽  
Zhenxue Dai ◽  
Gaoxuan Guo ◽  
Pietro Teatini

Abstract. Alluvial fans are highly heterogeneous due to complex depositional processes, which make difficult to characterize the spatial distribution of the hydraulic conductivity K. An original methodology is developed to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity in a three-dimensional setting by using geological and geophysical data. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the proposed approach. Due to the non-stationary property of the K distribution in the alluvial fan, a multi-zone parameterization approach is applied to analyze the conductivity statistical properties of different hydrofacies in the various zones. The composite variance in each zone is computed to describe the evolution of the conductivity along the flow direction. Consistently with the scales of the sedimentary transport energy, the results show that conductivity variances of fine sand, medium-coarse sand, and gravel decrease from the upper (Zone 1) to the lower (Zone 3) portion along the flow direction. In Zone 1, sediments were moved by higher-energy flooding, which induces bad sorting and larger conductivity variances. The composite variance confirms this feature with statistically different facies from Zone 1 to Zone 3. The results of this study provide insights to improve our understanding on conductivity heterogeneity and a method for characterizing the spatial distribution of K in alluvial fans.


2018 ◽  
Vol 12 (5) ◽  
pp. 1735-1744 ◽  
Author(s):  
Juri Palmtag ◽  
Stefanie Cable ◽  
Hanne H. Christiansen ◽  
Gustaf Hugelius ◽  
Peter Kuhry

Abstract. Soils in the northern high latitudes are a key component in the global carbon cycle, with potential feedback on climate. This study aims to improve the previous soil organic carbon (SOC) and total nitrogen (TN) storage estimates for the Zackenberg area (NE Greenland) that were based on a land cover classification (LCC) approach, by using geomorphological upscaling. In addition, novel organic carbon (OC) estimates for deeper alluvial and deltaic deposits (down to 300 cm depth) are presented. We hypothesise that landforms will better represent the long-term slope and depositional processes that result in deep SOC burial in this type of mountain permafrost environments. The updated mean SOC storage for the 0–100 cm soil depth is 4.8 kg C m−2, which is 42 % lower than the previous estimate of 8.3 kg C m−2 based on land cover upscaling. Similarly, the mean soil TN storage in the 0–100 cm depth decreased with 44 % from 0.50 kg (± 0.1 CI) to 0.28 (±0.1 CI) kg TN m−2. We ascribe the differences to a previous areal overestimate of SOC- and TN-rich vegetated land cover classes. The landform-based approach more correctly constrains the depositional areas in alluvial fans and deltas with high SOC and TN storage. These are also areas of deep carbon storage with an additional 2.4 kg C m−2 in the 100–300 cm depth interval. This research emphasises the need to consider geomorphology when assessing SOC pools in mountain permafrost landscapes.


Author(s):  
A. Moscariello ◽  
L. Marchi ◽  
F. Maraga ◽  
G. Mortara

Author(s):  
Paul J. Wright

Most industrial and academic geologists are familiar with the beautiful red and orange cathodoluminescence colours produced by carbonate minerals in an optical microscope with a cold cathode electron gun attached. The cement stratigraphies interpreted from colour photographs have been widely used to determine the post depositional processes which have modified sedimentary rock textures.However to study quartzose materials high electron densities and kV's are necessary to stimulate sufficient emission. A scanning electron microscope with an optical collection system and monochromator provides an adequate tool and gives the advantage of providing secondary and backscattered electron imaging as well as elemental analysis and distribution mapping via standard EDS/WDS facilities.It has been known that the incorporation of many elements modify the characteristics of the CL emissions from geological materials. They do this by taking up positions between the valence and conduction band thus providing sites to assist in the recombination of electron hole pairs.


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