Controls on modern fan morphology in Calabria, Southern Italy

doi:10.1016/S0169-555X(97)00079-2

Geomorphology

Volume 24, Issues 2–3, August 1998, Pages 169-187

https://doi.org/10.1016/S0169-555X(97)00079-2 Get rights and content

Abstract

Alluvial fans are widespread throughout Calabria, but only a minority display evidence of current activity. In order to understand if and to what extent fan types and their morphology are dependent on the physical environment, including characteristics and processes of the depositional site and drainage basin, we performed a series of discriminant analyses. These analyses used as classification factors the presence or absence of fill in the feeder channel, conditions of confinement by host terrain, the dominant depositional process (debris-flow or sheetflood); and morphometric attributes of fans and drainage basins as the discriminant function variables. In general, fan slope, area and width–length ratio, and, for basins, Melton's ruggedness number and source ratio, were the most useful variables for classification. Best results were obtained by discriminating the types of fan deposits and the presence versus absence of fill in the feeder channel, if the feeder source is singular. Fan morphology is controlled by constructional processes and is tightly linked to basin morphology. On the other hand, fan and basin morphology are also strongly dependent on the rock mechanical characteristics, with hard rocks imparting to the basin a high ruggedness and to fans a high gradient. Larger fans, however, are those where sheetflooding predominates. Results of discriminant analysis based on fan and basin variables are much more significant than those based on fan variables only. This means that the differences between characteristics of fan-and-basin systems are better defined than those between characteristics of fans only.

Introduction

Studies concerning the morphology, hydrology, and sedimentology of alluvial fans are numerous (e.g., Blissenbach, 1954; Bull, 1972; Nilsen, 1982; Harvey, 1988; Blair and McPherson, 1994), however, few studies have explored, on a probabilistic basis, the relationships between sedimentary facies, fan morphology, and drainage-basin geology and morphology (Melton, 1965; Kostaschuck et al., 1986; Marchi et al., 1993; Sorriso-Valvo and Sylvester, 1993). The purpose of this work is to examine the relationships between some of the distinctive morphometric elements of alluvial fans and their catchments, including fan facies, clast composition, area, length, overall slope and shape; and drainage-basin area, length, relief and ruggedness, and siting of the localized deposit source zone. We also explored the influence on fan morphology of the dominant depositional processes, and of the mechanical characteristics of the slope material, such as the rock hardness, as determined on a rank scale in the field. Our database includes a sample population of 68 cases.

Section snippets

Setting

Fan populations used in this study come from three study zones and two sites in north Calabria (Fig. 1). Calabria is the southernmost part of continental Italy and is characterized by a complex geological framework. Its geomorphology is strongly controlled by its bedrock geology and neotectonics. The bedrock geology in the central and southern part of the region consists of Neogene sedimentary rocks that cover a thick stack of allochthonous nappes. These nappes consist of crystalline rocks

Survey and measurement

We measured or assessed at 83 sites, the following alluvial-fan parameters: area, length, width, slope angle, and horizontal distance along the feeder channel from the active part of the catchment to the fan apex (Table 1). The latter parameter, called the source ratio (SRCR) is illustrated in Fig. 3. For the drainage basins we determined area, length, relief. We also determined the following non-parametric variables: presence or absence of sediment storage in the feeder channel, confinement

Alluvial-fan characteristics

Fans can be distinguished on the basis of several criteria. For the purpose of this paper, we differentiate the fans according to: (1) a mountain front or intramontane-valley setting, in which constraints are imposed by the host morphology in terms of confinement; (2) mechanical resistance of the clasts; and (3) the type of dominant depositional process (water flows vs. mass flows). Applying the fan terminology of Blair and McPherson (1994), we have designed as CI fans those whose deposits are

Statistical analysis of fan and drainage basin elements

We described the morphology of the fans and their drainage basins by means of variables which displayed their average and statistical dispersion parameters, including mean square residuals, minimum and maximum values (Table 2). The relationships between the different variables was first investigated through a correlation analysis (Table 3). The values of Pearson's correlation coefficient (r) are shown for the variables that could be measured for the whole sample population and, separately, for

Discussion

In Calabria, fans appear to have been much more active in the past. Indeed, most of the fans studied here are inactive, and some are reduced to remnants by dissection. The large majority of fans are of the CI type, indicating that rapid, high-magnitude and relatively rare processes, control fan evolution. Several fans are cast as inset fills in the main channel of older fans. This aggradation and dissection pattern commonly is observed in Calabria (Sorriso-Valvo, 1990) and elsewhere (Harvey,

Conclusions

In conclusion, it appears that fan morphology is controlled to varying degrees by different factors in the fan setting (mountain front versus intramontane valleys). In general, fan form is controlled by fan constructional processes and is tightly linked to basin morphology. Fans seem to be much more regular in the spatially constrained mountain front (Table 3), but the influence of constructional processes on fan morphology is higher in the intramontane valleys. On the other hand, fan and basin

Acknowledgements

The authors wish to thank T. Blair, A. Harvey, J. McPherson and H. Mills for fruitful discussion and suggestions.

References (23)

E Grüger
Pollenanalytiische Untersuchung zur würmzeitalichen Vegetationsgeschichte von Kalabrien (Süditalien)
Flora
(1977)
A.M Harvey
Aggradation and dissection sequences on Spanish alluvial fans: influence on morphological development
Catena
(1984)
T.C Blair et al.
Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies
J. Sediment. Res.
(1994)
E Blissenbach
Geology of alluvial fans in semi-arid regions
Geol. Soc. Am. Bull.
(1954)
W.B Bull
Recognition of alluvial fan deposits in the stratigraphic record. In: Rigby, J.K., Hamblin, W.K. (Eds.), Recognition of Ancient Sedimentary Environments.
SEPM Special Publication
(1972)
D Caloiero et al.
Le precipitazioni in Calabria (1921–1980)
Geodata
(1990)
P Ergenzinger
Regional erosion: rates and scale problems in the Buonamico basin, Calabria
Catena Suppl.
(1988)
A.M Harvey
Controls of alluvial fan development: the alluvial fans of the Sierra de Carrascoy, Murcia, Spain
Catena Suppl.
(1988)
Kock, G.S. Jr., Link, R.F., 1970. Statistical Analysis of Geological Data. Dover Publications, vol. 1, 375 pp. and vol....
R.A Kostaschuck et al.
Depositional process and alluvial fan-drainage basin morphometric relationships near Banff, Alberta, Canada
Earth Surf. Process. Landforms
(1986)

L Marchi et al.

Flow processes on alluvial fans in the eastern Italian Alps

Z. Geomorphol. Neue Fold

(1993)

Cited by (72)

Basin-scale reconstruction of late Pleistocene-Holocene fluvial landform evolution and its mechanisms in transitional areas between Taihang Mountain and North China Plain
2024, Palaeogeography, Palaeoclimatology, Palaeoecology
The processes and mechanisms of fluvial landform evolution, especially in the transitional zones between mountains and plains, are of great significance for predicting future regional sustainability and ecosystem stability in the basin. As a region of significant cultural and ecological importance, the transitional area between Taihang Mountain and North China Plain still has a limited understanding of the fluvial landform evolution. With detailed field surveys and 39 optically stimulated luminescence (OSL) ages of 14 sections, we reconstruct fluvial landform evolution in the southern piedmont of the Taihang Mountain since the late Pleistocene. The results show that two major fluvial processes occurred during 18–10 ka BP and 9–3 ka BP. Meanwhile, the late Pleistocene-Holocene can be divided into 5 intervals in the alluvial fan and floodplain areas, with corresponding ages of 3 ka BP, 9–3 ka BP, 10–9 ka BP, 18–10 ka BP, and before 20 ka BP, respectively. The results also indicate that the regional fluvial processes primarily result from climate change and tectonic activities, and secondarily result from sea level fluctuation. Additionally, the prehistoric settlement pattern was also shaped by the evolution of regional rivers. Our research is significant for understanding the evolution and mechanisms of fluvial landforms in transitional zones.
The global distribution and morphologic characteristics of fan-shaped sedimentary landforms on Mars
2022, Icarus
Citation Excerpt :
These include the Aklavik Range, Northern Canada (Palucis et al., 2021), Costa Rica (Saito, pers. comm.), Death Valley, CA (Blair, 1999), Central California (Bull, 1964), Japan (Saito and Oguchi, 2005), Nevada (Ferrill et al., 1996; Ritter et al., 2000), Owens Valley, CA (Whipple and Trayler, 1996), the Po Valley, Italy (Guzzetti et al., 1997), and southern Italy (Sorriso-Valvo et al., 1998). Several previous studies have used crater counting to find that alluvial fans were active during the Hesperian or Amazonian Periods.
Fan-shaped sedimentary landforms on Mars are important geomorphic markers of past water flow and characterizing the distribution and morphology of these features can yield insights into the planet's climatic evolution. We present a new database of 1501 martian fan-shaped sedimentary landforms that builds upon previous surveys and uses Context Camera images. This comprehensive global survey includes both alluvial fans and putative deltas, which we term scarp-fronted fan deposits (SFDs), across the entire martian surface. We classified each fan-shaped landforms based on their morphology as alluvial fans, channelized SFDs, smooth SFDs, and terraced SFDs. Martian alluvial fans are highly concentrated in the high southern tropical latitudes while SFDs are more common near the equator. Both alluvial fans and SFDs are found at lower elevations than Late Noachian to Early Hesperian valley networks, suggesting a climatic change in the locations of stable liquid water. Alluvial fans within impact craters are preferentially located on north, south, and east facing slopes, and are concentrated near the location of highest rim topographic relief; together these observations support orographically-influenced precipitation and snowmelt as a runoff source. For every fan in the database we collected morphologic data, which we compare with terrestrial alluvial fans. Relationships between alluvial fan catchment and fan morphology vary little across the martian surface, suggesting relatively similar processes. Although stratigraphic evidence of a deltaic deposition is lacking, previously conducted experiments along with the depositional basins of the channelized and terraced SFDs generally support deltaic formation. Crater counts indicate that many alluvial fans are within Hesperian and Amazonian impact craters, indicating that significant fluvial erosion occurred during Mars' relatively recent history.
Waters Divided: A History of Alluvial Fan Research and a View of Its Future
2022, Treatise on Geomorphology
Flows exiting confined valleys tend to deposit sediment in fan-shaped landforms. Where deposition is wholly or largely by the tractive forces of flowing water, these landforms are called alluvial fans. They are the product of the progressive division of water and sediment downfan, from slopes that may exceed 0.10 to distal slopes that may be below 0.01. Channel depths also tend to decline, from values that approach one to several meters at steep fanheads, to a few decimeters at distal fan margins. The result is a radiating, depositional ramp where confined or unconfined flows transport sediment from source basins to bounding streams, subsiding basins, or stable platforms. Where streams or subsiding basins consume the sediment supply from the source basin, the fan may approach a steady form whose extent and distal slope are set by stream location or subsidence rate. Where boundary conditions do not remove sediment, the fan may prograde out to long distances and low slopes (<0.01). Theoretical and experimental work over the past several decades support the notion that alluvial fan long-profiles become steeper as sediment supply increases or transport capacity decreases, and increasingly concave upward as the rate of bed material deposition decreases downfan. Grainsize distributions of alluvial fans seem to span the range observed in alluvial rivers, with no processes that uniquely identify them, apart from the distributary pattern of deposition. Bed sand cover tends to increase downfan in arid-region fans, with an absence of systematic downfan fining of coarser grain sizes. Surficial mapping and geochronology have demonstrated that fan deposition varies greatly through time, arguably from climate variations that alter hillslope sediment supply. The combination of surficial mapping and hydraulic modeling with high-resolution topography can now produce detailed flood susceptibility maps. The effective use of these maps to protect lives and property, however, depends on answering many of the enduring questions about the mechanics of how water and sediment divide down alluvial fans.
Sediment–water flows in mountain catchments: Insights into transport mechanisms as responses to high-magnitude hydrological events
2021, Journal of Hydrology
Citation Excerpt :
The flow types recognized from such surveys were regarded, similar to the processes inferred from the stratigraphic record, as representative of the ordinary flows characterizing each sub-reach of the stream. Morphometric parameters are powerful indicators for predicting the sediment–water flows occurring in response to high-magnitude events in mountain catchments (Kostaschuk et al., 1986; Jackson et al., 1987; Marchi et al., 1993; Calvache et al., 1997; Sorriso-Valvo et al., 1998; Marchi and Brochot, 2000; De Scally and Owens, 2004; Wilford et al., 2004; Santangelo et al., 2012; Bertrand et al., 2013). High-magnitude flow types are related to morphometric indexes, such as the channel slope, watershed length, and Melton’s number (i.e., the ratio of catchment relief to the square root of a catchment area; Melton, 1965).
Sediment transfer in mountain streams occurs via processes classified as debris flows, hyperconcentrated flows, debris floods, and water flows under the control of the water energy and the amount of involved sediment. Despite the extensive documentation of the channel changes caused by high-magnitude hydrological events, the analysis of the sediment–water flows occurring during such floods is currently a minimally explored issue. This study investigated how the transport mechanisms activated in a mountain stream during a high-magnitude flood differ from those triggered during ordinary floods. It also evaluated the effectiveness of three morphometric approaches in predicting high-magnitude flows expectable in a channel sub-reach. The study area is the Tegnas catchment (Dolomites, Italy), a mountain basin affected in 2018 by a severe hydrological event (Vaia Storm), whose recurrence interval is approximately 200 years. We determined the transport processes typifying the stream network in the catchment during ordinary floods through field surveys and direct monitoring and compared these flows with the high-magnitude flow types that occurred during the Vaia Storm. Additionally, we examined the flows predicted using the morphometric approaches for high-magnitude events. We observed water flow as a response to ordinary events occurring along the entire Tegnas main stem, whereas debris flow ordinarily determines sediment transfer at steep tributaries. During the Vaia Storm, water flow still dominated along the Tegnas Torrent, although debris flows and debris floods were also documented at several sub-reaches of the main stem. The morphometric approaches satisfactorily predicted debris flows but often failed to recognize the debris floods occurred during the high-magnitude 2018 flooding. The analysis of different flow types enabled us to infer relationships among transport mechanisms, hydraulic forcing, and channel dynamics and to gain new insights on the poorly explored debris flood processes. Water flows transitioned into debris floods under unit stream powers exceeding the threshold of 5000 to 5500 W m⁻² or downstream of sediment-injection points. The occurrence of debris floods, which caused higher channel widening than that induced by water flows, appeared to be facilitated by the presence of tributaries prone to debris flow occurrence connected to a receiving stream, the injection of fine material into the flows, and channels characterized by high slope and narrow section. The morphometric approaches enabled adequate first-order discrimination of expectable high-magnitude flows, but a more detailed characterization that includes field observations is necessary to understand the transport mechanisms that can affect a specific channel site during high-magnitude hydrological events for a more accurate and reliable definition of flood hazard at the local scale.
A review and prospects of debris flow waste-shoal land use in typical debris flow areas, China
2020, Land Use Policy
The shortage of land resources is one of the most pressing policy challenges faced by China, where many attempts have been made to increase the quantity and quality of land available for human use while protecting the environment. In the regard, the use of debris flow waste-shoal land (DFWSL) has achieved success. Although DFWSL is being developed and used, it has not yet received sufficient attention, and many challenges remain in the process of utilization. In order to improve awareness regarding DFWSL use and identify the opportunities and challenges, we evaluated the current policies and practices guiding the use and management of DFWSL in China using a combination of literature review and field studies. The results show that DFWSL development in China can be classified into three main stages: initial (risk assessment), development (analysis of soil properties and production potential), and mature (efficient and safe use). Ongoing research has placed increasing attention on the coordinated development of economic and ecological security, but some problems remain. First, the geomorphic nature of DFWSL is not always clearly recognized, leading to utilization that does not follow best practices. Second, the current theoretical system for development is insufficient, presenting barriers to scientifically informed and rational utilization. Third, there is a lack of clear and comprehensive policy guidance from the government. Therefore, we propose a new conceptual framework for DFWSL development that emphasizes a landscape-friendly trajectory that balances economic development and security. We expect this study to increase the focus on development in mountainous regions of China and encourage further investigation of the marginal land use potential in ecologically fragile areas where debris flows frequently occur.
Morphotectonics of the northern Bogd fault and implications for Middle Pleistocene to modern uplift rates in southern Mongolia
2020, Geomorphology
Assessing the activity of strike-slip faults is often facilitated by cumulative offsets of morphological features. The December 4th 1957 Mongolia earthquake, generally referred to as the “Gobi Altai” or “Bogd” earthquake, had M_W 8.1 and created long and complex surface ruptures of c. 350 km length along the Bogd fault that cuts across the foothills of the Gurvan Bogd mountains. Several left-laterally and vertically displaced Quaternary alluvial fans and morphogenic markers show cumulative offsets, allowing for an assessment of the effect of repeated earthquakes and active tectonics on landscape evolution. We propose to expand the active tectonic record along this fault up to a Middle Pleistocene time scale that spans regional climatic fluctuations, i.e. repeated glacial-interglacial cycles, and hence varying erosional and depositional rates.
Five main drainage areas crosscutting the North Ikh Bogd segment of the Bogd fault were analysed and compared in terms of hypsometry, drainage steepness and alluvial fan slope inclination. Along the mountain front, deposits from all drainages form multiple alluvial fan levels that reflect recurring deposition-incision cycles. Previously published ages, as well as the spatial distribution of these fan levels, suggest that their incision and abandonment is induced by regionally dominant climate fluctuations. However, the increase of fan slope angles over time and the increased intensity of sub-surface folding observed in ground-penetrating radar profiles, suggests that cumulative tectonic uplift also has a strong impact on alluvial fan morphology. Estimates of the increase of fan slope angles as a result of cumulative tectonic uplift imply that Middle Pleistocene to modern vertical slip rates along the North Ikh Bogd segment of the Bogd fault are in the order of 0.9–1 mm/yr. However, much slower vertical slip rates along individual fault segments, ranging between 0.06 ± 0.01 mm/yr and 0.28 ± 0.07 mm/yr, indicate that uplift of the Ikh Bogd plateau occurs as a result of distributed deformation across multiple parallel fault strands within bedrock as well as alluvial fans. Our results emphasise the importance of regional studies along active faults that take into account the complexity of surface ruptures as well as the occurrence of related structures that can accommodate deformation.

View all citing articles on Scopus

View full text

Controls on modern fan morphology in Calabria, Southern Italy

Abstract

Introduction

Section snippets

Setting

Survey and measurement

Alluvial-fan characteristics

Statistical analysis of fan and drainage basin elements

Discussion

Conclusions

Acknowledgements

Flora

Catena

Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies

J. Sediment. Res.

Geology of alluvial fans in semi-arid regions

Geol. Soc. Am. Bull.

Recognition of alluvial fan deposits in the stratigraphic record. In: Rigby, J.K., Hamblin, W.K. (Eds.), Recognition of Ancient Sedimentary Environments.

SEPM Special Publication

Le precipitazioni in Calabria (1921–1980)

Geodata

Regional erosion: rates and scale problems in the Buonamico basin, Calabria

Catena Suppl.

Controls of alluvial fan development: the alluvial fans of the Sierra de Carrascoy, Murcia, Spain

Catena Suppl.

Depositional process and alluvial fan-drainage basin morphometric relationships near Banff, Alberta, Canada

Earth Surf. Process. Landforms

Flow processes on alluvial fans in the eastern Italian Alps

Z. Geomorphol. Neue Fold