Elsevier

CATENA

Volume 158, November 2017, Pages 321-339
CATENA

Water driven processes and landforms evolution rates in mountain geomorphosites: examples from Swiss Alps

https://doi.org/10.1016/j.catena.2017.07.013Get rights and content

Highlights

  • Water driven processes in mountain environments are space and time-dependent.

  • Denudation rates are different depending on bedrock and geomorphic features.

  • Badlands-like landforms are meaningful as active/evolving passive geomorphosites.

  • Knowledge of geomorphic dynamics/rates is necessary to properly manage geoheritage.

Abstract

Geomorphic processes driven by water are particularly active in mountain environments, especially under the current climate conditions. Erosion and dissolution processes shape meaningful landforms, in different kinds of deposits and rocks, and in some cases they are classified as geomorphosites. Such landforms, especially earth pyramids and rock pillars, are usually characterized by a high scientific value (e.g., representativeness, ecologic support role) and by additional values (e.g., cultural and aesthetic value) contributing to the local geoheritage. Mountain geomorphosites are growing in importance within scientific community and their morphological evolution can affect the global value of the site itself (e.g., integrity). In this paper, after a first review on the terminology used for classifying landforms modelled by water runoff and on their meaning within the mountain environment, the results of a detailed research performed at two sample sites, included in the Swiss National Inventory of Geosites, are presented. The two study sites are representative respectively of: i) water runoff on glacial deposits shaping earth pyramids (Pyramides d'Euseigne); ii) water dissolution on gypsum rocks, modelling articulate karst landscapes (Pyramides de gypse du Col de la Croix). For each site, landforms evolution was investigated and denudation rates were estimated by means of different methods: iconographic material analysis, quantitative geomorphology and dendrogeomorphology on exposed roots. Despite the long-term, average rates obtained by means of roots exposure for both water runoff on glacial deposits (e.g., 5.8 mm/y) and dissolution on gypsum rocks (5.6 mm/y) are comparable. Moreover, a strict relation between the activity degree of processes, the integrity of the site and the assignment of geomorphosites to a specific category (i.e., active, passive or evolving passive) emerged from the results.

Introduction

Water driven processes acting along mountain slopes typically shape spectacular deeply dissected landscapes (i.e., badlands-like landforms; Bl-LFs), with distinctive features due to different substrates (i.e., rocks and deposits), that are various for lithology and texture, and different morphoclimatic contexts which they are inserted in. Mountain chains, like Apennines and Alps, are characterized by peculiar landscapes mainly modelled by running waters.

Widespread and famous are the Italian badlands, modelled in arid, semiarid and humid environments, known as “calanchi”. They are shaped mainly in Pliocene clays outcropping diffusely along the Apennines (Buccolini and Coco, 2013), within regions affected by strong seasonal climatic differences (Della Seta et al., 2009). Such landscapes are characterized by a pattern of dense close-up small valleys and gullies, with steep slopes and sharpened edges, and they are often associated with mostly rounded-edged landforms called “biancane” (Alexander, 1980).

In the Alpine contexts water runoff acts on widely diffuse glacial deposits, constituted by elements of different grain sizes, from boulders to silt and clay, shaping other peculiar badlands-like landforms, the earth pyramids. These are columnar landforms resulting from a big boulder protecting the underlying deposits from water runoff (Erikstad, 2006, Crosta et al., 2014).

Where rocks and deposits consist of soluble components (e.g., evaporites or limestone) also the chemical action of water contributes to the mountain landscape modelling. Where dissolution rates are high, as on gypsum (Nicod, 1976), or where landforms are undergoing to such process for a long time, residual pillars characterize mountain landscapes. These features are in some cases called “pyramids” as well. Hence, rocky pinnacles and earth pyramids may be considered convergent landforms from a geomorphological point of view, due to their similar shape.

The high mountain regions are among the most sensitive to climate change and abundant is the inherent literature (e.g., Evans and Clague, 1994, Chiarle and Mortara, 2001, Ballantyne, 2002, Fischer et al., 2006, Chiarle and Mortara, 2009, Mercier, 2009, Pelfini et al., 2014, Reynard et al., 2012a, Stoffel et al., 2014). Nowadays the action of water under different states (glacier ice, ground ice, melting waters from glaciers, permafrost, ice cores of moraines, rainfall) is regulated by the current climate warming trend, whose effects are inducing landform changes. Glacier ablation is responsible of the huge glacier retreats and of the transition from a glacial to a paraglacial system, subject to the morphological work of water driven and gravity processes (i.e., weathering, splash, rill and gully erosion, through-flow and piping) (e.g., Mercier, 2009, Stoffel et al., 2014). The response of paraglacial systems to climate change may span from immediate reaction until million years as indicated by Mercier (2009) who underlined also that paraglacial systems lifespan may depend on different factors, mainly from sediments at disposal to be reworked, climate conditions and geological constraints.

Therefore, in such evolving landscapes, landforms may be more or less preserved mainly depending on the substrate, which they are shaped in, on the age of landforms and on the rates of geomorphic processes they underwent.

A meaningful example of changing landforms in high mountain environment, and in paraglacial systems in particular, is represented by lateral and ground moraines, well known as key sites for the reconstruction of glacial advancing phases and for the observation of the following modifications under different geomorphic processes. Under the current climatic conditions, moraine ridges are affected by geomorphological instability (e.g., Curry, 1999, Hewitt, 1999, Chiarle and Mortara, 2001, Mortara and Chiarle, 2005, Curry et al., 2006, Mercier, 2009, Smiraglia et al., 2009). Over-incision of frontal moraines, erosion at the foot of the moraine slopes, concentrated linear erosion on the inner flank of lateral moraines, that generate new supra-imposed gullies (Bl-LFs), and burial, due to debris falls/flows, are the main processes affecting moraines on the whole Alpine range (Chiarle and Mortara, 2001). The re-modelling of glacigenic sediments has been recognized as one of the most important paraglacial slope adjustments consisting in increasing gravity processes and the sudden development of gully systems. Sediment transportation and formation of debris cones at the base of moraine inner slopes progressively lead to the reduction of the overall slope gradients and concavity in moraine profiles allowing them to reach a new equilibrium (Curry, 1999, Curry et al., 2006). Huge quantities of water released during intense rainfall events and/or from moraine ice core melting favour the process efficacy.

Also at lower altitudes slopes are mantled by glacial deposits, related to the older glaciations and now covered by soils; nevertheless also deeply dissected moraine ridges, continuously reworked by running and channelized waters and by human impact are present.

In this changing morphoclimatic context, rocky outcrops, characterized by erosion glacial landforms (e.g., roches moutonnées, glacial striae, subglacial potholes), when consisting in soluble lithotypes, can be reworked by karst processes (e.g. Chardon, 1996), whose action is added to the ones from other geomorphological active processes. In this context also pillars can develop, as mentioned before.

Water driven denudation processes are active with different rates in the mountain environment, from paraglacial areas as far as lower altitudes, depending on substrate, relief and climate factors (e.g., Delannoy and Rovera, 1996, Taminskas and Marcinkevicius, 2002). Denudation rates in mountain regions are significant at the drainage basin scale and crucial as they are strictly linked with the downstream physical and chemical water load (Descroix and Mathys, 2003). As reported by Chiarle and Mortara (2001), where huge coverage of loose debris are present extreme rainfall events can trigger mass wasting phenomena (as far as 5 × 106 m3 in a single event; Avisio catchment, Eastern Italian Alps). In general, the climate influence on the water runoff processes has been detected in terms of rainfall regime and typologies of rainfall events. In mountain environments the increase in runoff intensities during wet years, following dry ones, was detected (Bollati et al., 2012b, Bollati et al., 2016a, Bollati et al., 2016c and reference therein) and intense rainfall events demonstrated to trigger slope erosion (Bookhagen and Strecker, 2012) and mass wasting events (Guida et al., 2008).

In this framework, denudation rates (i.e., erosion and dissolution rates in the case of the Bl-LFs examined in the framework of the present research) vary in space and time and different values (i.e., local or averaged) may be obtained from different methods of measurement (i.e., direct and indirect) considering among them the natural data archives like tree rings. They are diversely efficient depending also on substratum and active processes.

In a geoheritage perspective, “pyramids” modelled by water driven processes on different substrates may be sites of great geological-geomorphological interest not only for their scientific importance but also for aesthetic reasons and for their links with different components of culture as literature and art, as well as socio-economic and tourist issues (e.g., Giusti, 2012, Bollati et al., 2016a). Deep is the current attention of the scientific community towards mountain geoheritage for both geoconservation and geotourism purposes due to i) its scientific meaning, ii) the presence of various geomorphological features, also in term of landforms activity degree, iii) the particular sensitivity of this environment to climate change and related hazards and iv) its highly aesthetic value (e.g., IAG – Network on Mountain Geomorphosites; Reynard et al., 2011, Reynard et al., 2016, Giusti et al., 2013, Ravanel et al., 2014, Bollati et al., 2016b, Reynard and Coratza, 2016). Hence, improving knowledge about mountain geoheritage evolution rates is crucial since the processes, which have shaped geomorphosites, can be the same that could degrade or destroy them (Hooke, 1994, Pelfini and Bollati, 2014, Bollati et al., 2016a). Analyses for estimation of changes in denudation rates are hence significant when considering changes in geoheritage for what concerns both conservation and impact and hazard assessment (Bollati et al., 2013, Bollati et al., 2016a).

In this perspective, after a short review on badlands-like landforms in mountain environment and their meaning in the geoheritage framework, two will be the aims to be pursued: i) to present the results of a multidisciplinary analysis on denudation rates characterizing selected geomorphosites shaped by water driven processes (i.e., physical and chemical) acting on different substrates (i.e., glacial deposits and soluble rocks); ii) to integrate site specific results in a discussion on spatio-temporal evolution of geomorphosites, and the related classification, according to geomorphic processes activity they are affected by.

Section snippets

A short review of badlands-like landforms in the framework of climate change

Terminology used for classifying badlands-like landforms is quite diversified (i.e., pyramids, pillars, towers; Perna, 1963) and usually local names are applied, often linked with tradition and legends. A short summary is reported in Table 1 and some pictures are illustrated in Fig. 1. Badlands-like landforms mainly derive from water action (physical erosion and chemical dissolution) on different kinds of substrates characterized by different textures (more or less heterometric in grain-size),

Study areas

The two study sites are included in the Swiss National Inventory of Geosites (SNIG) (Reynard et al., 2012b) (C and E, Fig. 4) and are located in the Western Swiss Alps. Both are named “Pyramids” even if the modelling process is different: i) Pyramides d'Euseigne - PE (Canton Valais) are earth pyramids shaped by water runoff on ancient glacial deposits; ii) Pyramides de gypse du Col de la Croix - PCC (Canton Vaud) are rock pillars deriving from chemical dissolution on gypsum outcrops. Both areas

Materials and methods

The sensitivity of an area to erosion may be determined considering mainly the morphometric factors (e.g., drainage density and setting, length of the slope or relief ratio, exposure and slope angle), the geological features (e.g., lithology, structures affecting drainage patterns) and the vegetation coverage (Latulippe and Peiry, 1996, Descroix and Mathys, 2003, Gyssels et al., 2005). In the Alpine environment, measurements of denudation rates, in relation with different substrates, have been

Morphometric measurements on historical photographs

The analysis of the iconographic material allows evidencing the progressive morphological changes of the site since the end of the 19th century (Fig. 9, Fig. 10).

One of the most evident changes is related to Group 1, characterized by the fall of a big boulder (A1 and A2, Fig. 9) that verified in the time interval 1906–1925. Therefore, after the fall of the block, the earth pyramid underlying the boulder has been evidently thinning more rapidly than the surrounding pyramids. In Group 1, the

Denudation rates at the study sites in comparison with literature data

In Table 7 a summary of the quantitative values of erosion on glacial deposits available in literature is reported, in comparison with those obtained in the present research.

According to Latulippe and Peiry (1996) the erosion on glacial deposits (as are Pyramides d'Euseigne) should be considered qualitatively “very strong” due to their unconsolidated structure. Nevertheless this is not true for very compact lodgement till, as observed in some cases for earth pyramids (Crosta et al., 2014),

Conclusions

From the short review on badlands-like landforms in mountain environment, it emerges that water driven processes related to climate are significant modelling agents in mountain environments. They can change in intensity and frequency, during different time periods and in relation with the involved substratum, producing landforms transforming through times. Results obtained from multidisciplinary and multitemporal analysis on mountain landforms, changing under water action, allowed us to

Acknowledgements

This study has been developed within the framework of the PRIN 2010–2011 project (grant number 2010AYKTAB_006) “Response of morphoclimatic system dynamics to global changes and related geomorphological hazards” (local leader C. Smiraglia and national leader C. Baroni). The Authors are grateful to the Canton of Valais administration (Landscape and Forest Service, director: M. Olivier Guex) for authorizing us to investigate the protected area of Pyramides d'Euseigne and to the Ollon Municipality

References (93)

  • F. Gutiérrez et al.

    Surface morphology of gypsum karst

    Treatise Geomorphol.

    (2013)
  • K. Hewitt

    Quaternary moraines vs catastrophic rock avalanches in the Karakoram Himalaya, northern Pakistan

    Quat. Res.

    (1999)
  • J.W. Poesen et al.

    Effects of rock fragments on soil erosion by water at different spatial scales: a review

    Catena

    (1994)
  • M. Stoffel et al.

    Climate change impacts on mass movements—case studies from the European Alps

    Sci. Total Environ.

    (2014)
  • J. Alestalo

    Dendrochronological interpretation of geomorphic processes

    Fennia

    (1971)
  • D.E. Alexander

    I calanchi. Accelerated erosion in Italy

    Geography

    (1980)
  • M. Avanzini et al.

    Geomorphosites in Trentino: a first census

    Il Quaternario

    (2005)
  • J.A. Ballesteros-Cánovas et al.

    Combining terrestrial laser scanning and root exposure to estimate erosion rates

    Plant Soil

    (2015)
  • D. Bianco et al.

    Tutela e valorizzazione delle aree carsiche italiane nelle rocce evaporitiche: problemi e prospettive

  • Y. Biedermann et al.

    Typologie des sols sur gypse et végétation associée en Suisse

    Bull. Société Vaudoise Sci. Nat.

    (2014)
  • J.M. Bodoque et al.

    Source of error and uncertainty in sheet erosion rates estimated from dendrogeomorphology

    Earth Surf. Process. Landf.

    (2015)
  • I. Bollati et al.

    A geomorphosites selection method for educational purposes: a case study in Trebbia Valley (Emilia Romagna, Italy)

    Geogr. Fis. Din. Quat.

    (2012)
  • I. Bollati et al.

    Assessment and selection of geomorphosites and trails in the Miage Glacier Area (Western Italian Alps)

    Environ. Manag.

    (2013)
  • I. Bollati et al.

    The role of the ecological value in geomorphosites assessment at the debris-covered Miage Glacier (Western Italian Alps) based on a review of 2.5 centuries of scientific study

    Geoheritage

    (2015)
  • I. Bollati et al.

    A methodological proposal for the assessment of cliffs equipped for climbing as a component of geoheritage and tools for Earth Science education: the case of the Verbano-Cusio-Ossola (Western Italian Alps)

  • I. Bollati et al.

    Runoff impact on active geomorphosites in unconsolidated substrate. A comparison between landforms in glacial and marine clay sediments: two case studies from the Swiss Alps and the Italian Apennines

    Geoheritage

    (2016)
  • I. Bollati et al.

    Multitemporal dendrogeomorphological analysis of slope instability in Upper Orcia Valley (Southern Tuscany, Italy)

    Geogr. Fis. Din. Quat.

    (2016)
  • V. Brazier et al.

    Making space for nature in a changing climate: the role of geodiversity in biodiversity conservation

    Scott. Geogr. J.

    (2012)
  • J. Brilha

    Inventory and quantitative assessment of geosites and geodiversity sites: a review

    Geoheritage

    (2016)
  • M. Chardon

    Évolution récente des karsts de la Vanoise orientale

  • M. Chardon

    La mesure de l'érosion dans le gypse anhydrite des Alpes Françaises du Nord. Méthodes et état des connaissances

    Rev. Géogr. Alp.

    (1996)
  • M. Chiarle et al.

    Esempi di rimodellamento di apparati morenici nell'arco alpino italiano

    Suppl. Geogr. Fis. Dinam. Quat

    (2001)
  • M. Chiarle et al.

    Geomorphological impact of climate change on Alpine glacial and periglacial areas

  • A.A. Cigna

    A classification of karstic phenomena

    Int. J. Speleol.

    (1978)
  • A.A. Cigna

    Some remarks on phase equilibria of evaporites and other karstifiable rocks

    Le Grotte d'Italia

    (1986)
  • L. Comănescu et al.

    Public perception of the hazards affecting geomorphological heritage – case study: the central area of Bucegi Mts. (Southern Carpathians, Romania)

    Environ. Earth Sci.

    (2015)
  • S. Coutterand

    The Lateglacial of Hérens valley (Valais, Switzerland): palaeogeographical and chronological reconstructions of deglaciation stages

    Quat. Int.

    (2012)
  • R. Crosta et al.

    Earth pyramids: precarious structures surviving recurrent perturbations

  • A.M. Curry

    Paraglacial modification of slope form

    Earth Surf. Process. Landf.

    (1999)
  • A.M. Curry et al.

    Paraglacial response of steep, sediment-mantled slopes to post-‘Little Ice Age’ glacier recession in the central Swiss Alps

    J. Quat. Sci.

    (2006)
  • J.J. Delannoy et al.

    Conclusion: L'érosion dans les Alpes occidentales: contribution à un bilan des mesures et des méthodes/erosion in the western alps: a contribution to an assessment of measurements and methods

    Rev. Géogr. Alp.

    (1996)
  • L. Descroix et al.

    Processes, spatio-temporal factors and measurements of current erosion in the French southern Alps: a review

    Earth Surf. Process. Landf.

    (2003)
  • G. Diolaiuti et al.

    Changing glaciers in a changing climate: how vanishing geomorphosites have been driving deep changes in mountain landscapes and environments

    Géomorphologie

    (2010)
  • L. Erikstad

    Protection and management of finite nature resources representing active geoprocesses Case: Kvitskriuprestin natural monument, Norway

  • L. Fischer et al.

    Geology, glacier retreat and permafrost degradation as controlling factors of slope instabilities in a high-mountain rock wall: the Monte Rosa east face

    Nat. Hazard Earth Sys.

    (2006)
  • P. Forti

    Gypsum karst

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