Relief Evolution of Landslide Slopes in the Kamienne Mts (Central Sudetes, Poland) – Analysis of a High-Resolution DEM from Airborne Lidar

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Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Relief evolution of landslide slopes in the Kamienne Mts (Central Sudetes, Poland) – analysis of a high-resolution DEM from airborne LiDAR

Aleksandra Osika*, Małgorzata Wistuba, Ireneusz Malik

Faculty of Earth Sciences, University of Silesia in Katowice, Bedzinska 60, 41-200 Sosnowiec, Poland * corresponding author: [email protected]

Received: 5th November, 2017 Accepted: 9th January, 2018

Abstract The aim of the study is to reconstruct the development of landslide relief in the Kamienne Mountains (Central Sudetes, SW Poland) based on a DEM from LiDAR data. Analyses of relief and geological maps in ArcGIS 10.5 and of slope cross-sections in Surfer 14 allowed to distinguish different types of landslide relief, developed in latites and trachybasalts lying above claystones and mudstones. The types vary from small, poorly visible landslides to vast landslides with complex relief. They were interpreted as consecutive stages of geomorphic evolution of hillslope-valley topography of the study area. Two main schemes have been established which explain the development of landslide slopes in the Kamienne Mts: (1) upslope, from the base of the slope towards the mountain ridge and (2) downslope, beginning on the top of the mountain ridge. The direction of landslide development depends on the thickness of volcanic rocks in relation to underlying sedimentary rocks. When the latter appear only in the lowest part of the slope, landslides develop upslope. If sedimentary rocks dominate on the slope and volcanic rocks form only its uppermost part, landslides develop downslope. The results show that landsliding leads to significant modifications of relief of the study area, including complete degradation of mountain ridges.

Key words: Landsliding, relief evolution, Kamienne Mountains, DEM, LiDAR

Introduction catchment morphology. This may include even complete deformation of valley floors (Korup Mass movements occur not only in high et al. 2010). To emphasise the role of mountain areas (e.g. Cendrero and Dramis landsliding as a formative process, Crozier 1996; Guglielmi and Cappa 2010; Shroder Jr. (2010) proposed a term “landslide et al. 2011; Pánek et al. 2017; Schwartz et al. geomorphology system” in which “landslides 2017) but also in regions with lower are the dominative forms and process by topography (e.g. Wistuba et al. 2015; Yenes et governing the mechanisms, rhythm and pace of al. 2015). Their importance for relief geomorphic change, in time and space”. development can be significant and appear Geomorphological significance of landsliding through developing new landforms and was previously highlighted also by Cendrero influencing other geomorphic processes, and Dramis (1996). They indicated that in fluvial in particular (e.g. Cendrero and Dramis some cases, like the Canary Islands with vast 1996; Korup et al. 2010). Korup et al. (2010) landslides in volcanic rocks, landsliding may claim that landslides are the main source of be the most important process in the sediments in the mountain areas. Vast topography evolution. landslides modify slope curvature and Despite potentially significant role of inclination, and take major part in reshaping landsliding in moulding hillslope-valley

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

systems, the process is often left unmentioned based only on relief characteristics and the in theories of landscape evolution, not only in need for further, detailed studies to confirm the earliest models (e.g. Davis 1899; Penck potential findings. 1953; Klimaszewski 1967), but also in the later ones (e.g. Lavé and Avouac 2001; Kirby et al. Study area 2003; Snyder et al. 2003; Clark et al. 2004). Moreover, according to Korup et al. (2010), it The study area is located in the Kamienne is a common view that the fluvial network Mts in the Central Sudetes, SW Poland (Fig. controls the slope system, but the landsliding 1). Landslides in this area were described for cannot influence fluvial processes. However, the first time in the 1970s (Grocholski 1972; today mass movements are more and more Pulinowa 1972; Pulinowa and Mazur 1971). often included in schemes of hillslope-valley The results of geomorphology mapping were systems development (e.g. Skempton 1953; presented by Synowiec (2003). Many papers Skempton and Delory 1957; Bisci et al. 1996; describing arrangement, activity and types of Brooks et al. 2002; Azañón et al. 2005; Lévy et movement of these landslides were published al. 2012; Zerathe and Lebourg 2012; Migoń et after 2010 (Kasprzak and Traczyk 2012; al. 2013; Wistuba 2014; 2015), including Migoń 2010; Migoń et al. 2010, 2014a-c). The research conducted in the Carpathian Mts, significant role of landsliding in study area was southern Poland (e.g. Starkel 1960; Ziętara proved by Kasprzak et al. (2016) who used 1974; Kotarba 1986; Gorczyca 2010; Gorczyca LiDAR data to describe the case of a Jeleniec- et al. 2014). Rogowiec mountain ridge degraded by mass Today analyses of landslide relief and the movements. role of landsliding in relief development can be facilitated by airborne LiDAR data. High- resolution DEMs from LiDAR data allow not only to identify individual forms, but also to determine their types of movement and to monitor landslide-affected areas (e.g. Jaboyedoff et al. 2012; Migoń et al. 2013, 2014b). The study attempted to reconstruct the evolution of landslide slopes in a selected part of the Kamienne Mts by analysing their relief. In particular the study aimed to: - distinguish different types of landslide slopes based on their relief characteristics: the degree of landslide development and subsequent Fig.1. Location map of the study area in the reshaping, e.g. by linear erosion, slopewash, Sudetes. creep, particle fall and - analyse relief of landslide-effected slopes in In this paper we have analysed the central- relation to bedrock. eastern part of the Kamienne Mts: the Suche We also tested the possibility to establish Mts (Waligóra, 936 m a.s.l.) and Lesista Range consecutive stages of relief evolution in the (Lesista Wielka, 854 m a.s.l.). The bedrock of study area depending on geological conditions the Kamienne Mts consists of early Permian and geomorphological conditions, with the volcanic and subvolcanic rocks: rhyolite, latite, reservations about the reliability of the model trachybasalts and tuff lying on sedimentary

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

rocks: Carboniferous to early Permian prepare shaded relief maps (lighting azimuth claystones, mudstones, sandstones and 315° and 135°) and slope maps (degrees) in conglomerates (Bossowski et al. 1995). In the ArcGIS 10.5 (Fig. 2). Each time data were study area mountain ridges are dissected by classified with Natural Breaks (Jenks) method. short, V-shaped or flat-bottomed valleys The aforesaid maps were a basis for on screen (Kasprzak and Traczyk 2012). Relief of the digitalization of landslide areas using Kamienne Mts reflects contrast in erosion morphological criteria suggested by Dickau et resistance of rocks, thus mountain ridges al. (vide Migoń et al. 2014a): represent more resistant volcanic rocks and - linear or arched scarps in the upper part of river valleys are incised into sedimentary slopes, rocks. Mean slope angles are 20-40°, but - steep-alike arrangement of landslide blocks, locally they exceed 60° (Migoń et al. 2010). - hummocky, irregular relief of the lower parts The climate of the Kamienne Mts is cool of slopes, temperate (Migoń et al. 2014c). In the period - steep landslide toes and 1977-2007 the mean annual temperature was - wide valley floors with irregular relief. 5.5°C and the mean annual precipitation was According to Migoń et al. (2014a), 776 mm at the nearby weather station in another important diagnostic feature is the Mieroszów (500 m a.s.l.) (Migoń et al. 2014c). contrast between varied landslide relief and smooth surface of surrounding inactive slopes. Materials and methods Landslides outlined in this study were divided into “distinct” (with clear relief) and Analysis of landslides location and their extent “indistinct” (with unclear relief). Further was carried out using GIS software: ArcGIS detailed analysis of landslide topography was 10.5 and Surfer 14. The studies were based on based on relief maps combined with scanned a high resolution DEM (1 m x 1 m) from “Bare geological maps (1:25 000) in ArcGIS 10.5 Earth” LiDAR data. The data were obtained (Fig. 3) and on 70 slope cross-sections in from Central Office for Geodetic and Surfer 14. This was a basis of classifying Cartographic Documentation (CODGIK) in landslides according to their bedrock and Poland. The scanning has been made in 2011- distinguishing different types of landslide 2014. The point density was 6 per 1 m2 and the relief and then interpreting these types as maximum vertical error was 30 cm. The data consecutive stages of geomorphic evolution of were obtained as *.asc files and transformed relief in the study area (Figs. 4, 5). into a point cloud. Then, DEM was used to

Fig.2. Example of landslide-affected slopes on shaded relief maps (A – standard 315° lightning, B – 135° lightning) and slope map (C) (DEM from airborne LiDAR).

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.3. Bedrock of the study area and a shaded relief map from LiDAR data with landslide extent.

Fig.4. Distribution of slope cross sections representing types of landslide relief in latites. Each color of cross sections lines marks a different type of landslide relief (L1-L6) (cross sections: Fig. 7).

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.5. Distribution of slope cross sections representing types of landslide relief in trachybasalts. Each color of cross sections lines marks a different type of landslide relief (B1-B7) (cross sections: Fig. 8).

Results with complex relief. The mean landslide rate (amount of landslides per area unit) is 1.16 per General features of landslide relief of the study 1 km2 and the mean landslide area is 0.10 km2. area Detailed analysis of landslide arrangement in relation to geology of the Kamienne Mts Analysed part of the Kamienne Mts covers allowed to distinguish three groups of 34.46 km2 including 3.93 km2 of landslide landslides, based on types of rocks in which relief (11.4% of the study area). Analysis of the main scarps developed: latites, shaded relief maps and slope maps allowed us trachybasalts and tuffs (Fig. 6). to distinguish 40 landslides (Fig. 3). Three of Almost three quarters of landslides in the them are vast landslide slopes (0.46-0.64 km2) study area (71% of landslide-effected areas)

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

occur on the northern, north-eastern and north- IV). Landslides developed in tuffs have been western slopes. Only 11% of landslides omitted in further analysis as there are only developed on the southern slopes and 2% on few of them (5). south-eastern slopes (Fig. 6). The analysis of The L1 type of landslide relief developed landslide distribution in relation to the geology in latites is represented by small, poorly of Kamienne Mts has shown that landslides developed landslides in the lower part of developed in latites generally occurs on the slopes with indistinct head scarps and distinct, northern slopes. Landslides developed in single toes (Figs. 4, 7 A-A′, B-B′). As opposed trachybasalts occurs on both northern and to the other types, this landslides are very southern slopes. The former are, however, shallow and occur on slopes that consists only more extensive and have more complex relief of volcanic rocks. Other types of landslides of the landslide body. Landslides developed in developed in the latites (L1-L6) were tuffs usually occurs on northern or north- distinguished on slopes where sedimentary eastern slopes. Irrespective of the bedrock, rocks occur at the contact with valley floor. landslides on the northern and eastern slopes The L2 type refers to small landslides with are generally more extensive and have more poorly developed head scarps in the lower part complex relief. of slopes and distinct toes (Figs. 4, 7 C-C′, D- D′). The L3 type of landslides have clear, steep Types of landslide relief distinguished based head scarps in the middle part of slopes and on LiDAR data complex relief of the landslide body (Figs. 4, 7 E-E′, F-F′). The L4 type are vast landslides Slope cross sections allowed to distinguish with steep, high head scarp in the upper part of different types of landslide relief present in the the slope and complex relief of the landslide study area (Figs. 7, 8). For landslides body. The L4 type of landslides were developed in latites (L types) these features additionally divided into two subtypes: L4a – include: total length and location on the slope, vast landslides with fresh relief, very steep and relief characteristic of the main scarp, crown high head scarps in the uppermost part of the cracks, fragmentation of the landslide body, slopes, crown cracks, trenches and active scree presence of minor scarps and a scree from (Figs. 4, 7 G-G′), and L4b – vast landslides secondary particle fall (Table 1.). For with less distinct relief, steep and high head landslides developed in trachybasalts (B types) scarps in the uppermost part of the slopes and these features include: location on the slope, with complex relief of the landslide body relief characteristic of the main scarp, trench, (Figs. 4, 7 F-F′). Finally, vast landslides of the fragmentation of the landslide body and L5 type have head scarps reaching the presence of a minor scarps (Table 2.). The topographic culmination of a mountain ridge criteria of the performed classifications are not (Figs. 4, 7 I-I′), while landslides of the L6 type the same for L and B types due to significant have head scarps which have exceeded differences in their relief. For each type we mountain ridges and affected the backslopes have performed the classification using the (Figs. 4, 7 J-J′, K-K′). most diagnostic relief features, i.e. the most The B1-B5 types developed on slopes differing features of relief within each type. where trachybasalts form only a thin cap over a The types of landslide relief were outlined in slope composed of sedimentary rocks (Fig. 3). relation to reference slopes not affected by The B1 type of landslide relief refers to poorly landsliding. In the study area these stable developed, shallow trenches in the uppermost slopes are steep (20-30°), straight or convex parts of slopes with smooth, undisturbed and have smooth surface (Fig. 7 I-II, Fig. 8 III- surface below (Figs. 5, 8 L-L′, M-M′). The B2

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

type are clearly visible, widened trenches in - small landslides with poorly developed head the uppermost parts of slopes with undulating, scarps in the lower part of slopes and distinct disturbed surface below (shallow, elongated toes (L2 and B6 types), depressions and low ridges parallel to slope - landslides with clear, steep head scarps in the inclination) (Figs. 5, 8 N-N′, O-O′). The B3 middle part of slopes and complex relief of the type refers to distinctly slided single colluvial landslide body (L3 type), blocks with similar ridges and hollows as - vast landslides with high, steep head scarps in previously mentioned (Figs. 5, 8 P-P′, Q-Q′). the upper part of slopes, complex relief of the Landslides of the B4 type are vast and have landslide body and screes (L4 type), steep head scarps, reshaped by successive - vast landslides with head scarps reaching the events of landsliding (Figs. 5, 8 R-R′, S-S′). topographic culmination of the mountain ridge Then, the B5 type refers to small, poorly (L5 and B7 types), visible scarps with shallow colluvial blocks - landslides with head scarps exceeding the below (Figs. 5, 8 T-T′, U-U′). Landslides of the topographic culmination of the mountain ridge B6 and B7 types have different topography (L6 type). compared to the previous five types and The scheme was based on landslide relief developed in slopes of different bedrock where found in Włostowa – Kostrzyna – Suchawa – trachybasalts predominated over underlying Waligóra range and on slopes of Dzikie Turnie sedimentary rocks. The B6 type are landslides and Stożek Wielki (Figs. 4, 5). Landsliding with head scarps in the lower part of slopes, starts in the lower part of a slope, near the similar to landslides of the L2 type in latites geological boundary between volcanic (latites (Figs. 5, 8 V-V′, W-W′; Figs. 4, 7 C-C′, D-D′). or trachybasalts) and sedimentary rocks The B7 type are landslides with head scarps in (claystones and mudstones) (Fig. 9a). The the upper part of slopes, similar to the L5 type scheme occurs regardless of the type of (Figs. 5, 8 X-X′, Y-Y; Figs. 4, 7 I-I′). volcanic rocks in which the head scarp developed. The necessary condition is Established schemes of landslide relief considerable thickness of volcanic rocks in development in the Kamienne Mts relation to underlying sedimentary rocks in the base of slopes (Fig. 7 L2-L6, Fig. 8 B6-B7). Presented above detailed analysis of the types The slopes are generally stable when they of landslide slopes in the study area allowed us consist only of volcanic rocks. Very few, to establish consecutive stages of their shallow landslides occur in such cases (L1 development. We have established the two type). Significant landslide activity begins main schemes of the evolution of landslide when fluvial erosion dissects volcanic rocks slopes, based on its up- and downslope and exposes weak, plastic sedimentary rocks at direction (Figs. 9, 10). the base of slopes. Then first landslides develop near the valley floor (L2 and B6 types, 1. Upslope scheme of landslide relief evolution Fig. 9a). This process undermines the slope at its basis and makes its upper part unstable. The Landslide evolution in the upslope scheme first event of landsliding promotes further begins in the lower part of the slope, next instability of the slope and causes successive landslides expand upslope. The scheme is landslides. The headscarp migrates upslope in represented by the following, earlier consecutive events of landsliding and the established in the study area, types of landslide landslide expands upward. In the following relief (Fig. 9): stages (L3-L4 types) the height and inclination - stable slope, not affected by landsliding, of headscarps increase (Fig. 9 b-c). Then,

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

particle fall and rockfalls lead to reshaping and - clearly visible, widened trenches in the retreat of headscarp (now a rock wall) and to uppermost parts of slopes with undulating, covering landslide bodies with screes (L4 disturbed surface below (shallow, elongated type). In the next stage head scarps reach the depressions and low ridges parallel to slope topographic culmination of the mountain ridge inclination (B2 type), (L5 type) (Fig. 9d). While landsliding - distinctly slided single colluvial blocks with continues to expand into disturbed mountain undulating, disturbed surface below (shallow, ridge the head scarp exceeds the topographic elongated depressions and low ridges parallel culmination of the mountain ridge (L6 type) to slope inclination) (B3 type), (Fig. 9e). Such case have been found on the - vast landslides with steep head scarps northern slope of Włostowa Mt, where reshaped by successive events of landsliding landsliding have led to almost complete (B4 type), degradation of the mountain ridge (Figs. 7, 9 J- - small, poorly visible scarps with shallow J′, K-K′). colluvial blocks below (B5 type). The scheme was based on landslide relief 2. Downslope scheme of landslide relief found in Klin – Turzyna – Jeleniec range (Fig. evolution 5). In this model landsliding is also initiated near the boundary between volcanic Landslide evolution in the downslope model (trachybasalts) and sedimentary rocks begins at the top of the mountain ridge, next (claystones and mudstones) which, however, is landslides expand downslope. The scheme is located in the upper part of a slope (Fig. 10a). represented by the following, earlier This scheme takes place on slopes which established in the study area, types of landslide consists mainly of sedimentary rocks covered relief (Fig. 10): by a thin cap of volcanic rocks. At first, a - stable slope, not affected by landsliding, shallow trench occurs within trachybasalts at - poorly developed, shallow trench in the the top of a mountain ridge while the rest part uppermost parts of the slope with smooth, of the slope has smooth, undisturbed surface undisturbed surface below (B1 type), (B1 type) (Fig. 10a). While the landslide

Fig.6. Diversity of landslides area in latites (A), trachybasalts (B), tuffs (C), in general (D), and exposure of landslide-effected areas in latites (A′), trachybasalts (B′), tuffs (C′), and in general (D′).

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.7. Cross sections of a stable (I-II) and landslide slopes (A-A′, B-B′…) representing types of relief developed in latites. Arrow indicate enlarged cross sections of a particular slope.

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.8. Cross sections of a stable (III-IV) and landslide slopes (L-L′, M-M′…) representing types of relief developed in trachybasalts. Arrows indicate enlarged cross sections of particular slopes.

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.9. A scheme of upslope landslide evolution. Letters a-e stand for consecutive stages of landslides development. Arrows indicate enlarged cross sections of particular slopes. Profile descriptions (e.g. D-D’, I-II) indicate their location in the field (see Figs. 4-5).

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.10. A scheme of downslope landslide evolution. Letters a-e stand for consecutive stages of landslides development. Arrows indicate enlarged cross sections of particular slopes. Profile descriptions (e.g. L-L’, III-IV) indicate their location in the field (see Figs. 4-5).

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Tab.1. Types of relief and diagnostic features of landslides developed in latites. Number of analysed slope Location on the Relief characteristic of the main Crown Minor Diagnostic features profiles Area [km²] Total length [m] Fragmentation of the landslide body Scree slope scarp cracks scarps Types of relief representing each type L1 - small, poorly developed landslides in the lower part of slopes with indistinct head scarps and distinct, single Lower part Poorly developed, very low Single toe with regular relief toes 7 0.004-0.038 60-300 L2 - small landslides with poorly developed head scarps Lower part Poorly developed, low (15-20 m) Irregular, undulant relief, distinct toe in the lower part of slopes and distinct toes 4 0.025-0.045 150-250

L3 - landslides with clear, steep head scarps in the middle Distinct, medium high (20 m), Middle-lower part Transverse slid blocks, indistinct toe + part of slopes and complex relief of the landslide body steep (to 65°) 5 0.006-0.040 42-304 L4a - vast landslides with fresh relief, very steep and high High (to 30 m), steep (to 75°), head scarps in the uppermost part of the slopes, crown Upper-lower part + Distinct transverse slid blocks + + rock wall cracks, trenches and active screes 1 0.090-0.250 489-678 L4b - vast landslides with less distinct relief, steep and High (to 25 m), steep (to 60°), Transverse slid blocks, hummocky high head scarps in the uppermost part of the slopes and Upper-lower part + + rock wall topography, erosional incisions with complex relief of the landslide body 3 Whole slope from Transverse slid blocks, hummocky L5 - vast landslides with head scarps reaching the the mountain ridge High (to 25 m), steep (to 50°) topography, erosional incisions, indistinct + topographic culmination of a mountain ridge to the slope base toe 2 0.164 500 Distinct transverse slid blocks, mid-slope Whole mountain L6 - vast landslides with head scarps exceeding the Medium high (15-25 m), steep depression, irregular, indistinct relief with ridge (including the + topographic culmination of a mountain ridge (40-60°) erosional incisions in the lower part of the opposite slope) landslide body 3 0.196 615

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Tab.2. Types of relief and diagnostic features of landslides developed in trachybasalts. Number of analysed slope Diagnostic features profiles Relief characteristic of the Fragmentation of the Location on the slope Trench Minor scarps representing main scarp landslide body Types of relief each type

B1 - poorly developed, shallow trenches in the uppermost Poorly developed, shallow Smooth, undisturbed parts of the slopes with smooth, undisturbed surface Top of the mountain ridge Indistinct (7 m), 35 m wide surface below 2

B2 - clearly visible, widened trenches in the uppermost Low ridges and shallow, Clearly visible, widened to parts of the slopes with undulating, disturbed surface Top of the mountain ridge-upper elongated depressions Low (<10 m), steep a rock bench (20-60 m below (shallow, elongated depressions and low ridges part of the slope parallel to slope wide) parallel to slope inclination) inclination 4 Low ridges and shallow, B3 - distinctly slided single colluvial blocks with elongated depressions Top of the mountain ridge-upper undulating, disturbed surface below (shallow, elongated Medium-high (>20 m), steep parallel to slope part of the slope depressions and low ridges parallel to slope inclination) inclination, slided single 5 colluvial block below Hummocky topography B4 - vast landslides with steep head scarps reshaped by Whole slope from the mountain Medium-high (>20 m), steep with distinct subsequent successive events of landsliding ridge to the slope base colluvia 6 B5 - small, poorly visible scarps with shallow colluvial Top of the mountain ridge Indistinct, low Shallow colluvial blocks blocks below 4 Transverse slid blocks, B6 - landslides with head scarps in the lower part of the Medium-high (15-25 m), Middle-lower part irregular, hummocky + slopes and distinct transverse slid blocks below steep topography, distinct toes 4

B7 - landslides with head scarps in the upper part of the Medium-high (15-30 m), Irregular, hummocky slopes and irregular, hummocky topography of the Upper-lower part + steep topography, distinct toes landslide body 3

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

trench is widening, the surface of the upper head scarp exceeds the topographic part of the slope becomes undulated with culmination of the mountain ridge, leading to shallow, elongated depressions and low ridges its degradation. So far few schemes of upslope parallel to slope inclination (B2 type) (Fig. evolution of landslides have been described in 10b). These ridges occur as a result of literature. These type of schemes have been squeezing out plastic sedimentary rocks from developed by e.g. Skempton (1953) for small below overlying rigid volcanic rocks. In the catchments in the London Clay formation, next stage a rocky bench slides down and Brooks et al. (2002) in New Zealand, Lévy et gradually disintegrates (B3 type) (Fig. 10c). al. (2012) for Chacoura valley in Canada, Then, a steep scarp remains at the crown of a Wistuba (2014) in the Hrubý Jeseník Mts and landslide with some landslide relief present in the Moravskoslezské Beskydy Mts and below (B4 type) (Fig. 10d). In the following Yenes et al. (2015) for Duero and Pisuerga stage the main scarps retreats through a series valleys in Spain. However, these authors of shallow slides (B5 type). As a results only a represents different views about the impact of short scarps can be found on the top of a landslides on the slope stability. Some of them mountain ridge with poorly visible remains of claim that landsliding leads to increase of the colluvial blocks below (Fig. 10e). slope stability (e.g. Skempton 1953; Brooks et al. 2002). The others maintain that the first Discussion landsliding episode precedes the next ones and contributes to the further instability of the The detailed analysis of landslide relief based slope, like in the Kamienne Mts (e.g Sánchez on DEM from airborne LiDAR allowed to et al. 1999; Wistuba 2014; Yenes et al. 2015). develop two main schemes of landslide However, as opposed to the Kamienne Mts, evolution in the Kamienne Mts: (1) upslope, landslides expanding upslope, described so far beginning at the base of a slope (Fig. 9) and (2) in literature, usually develop in sedimentary downslope, beginning from the top a mountain rocks (Skempton 1953; Azañón et al. 2005; ridge (Fig. 10). Lévy et al. 2012; Yenes et al. 2015). In the In the first scheme landsliding begins in Kamienne Mts landslides are initiated by slow the lower part of the slope, near the boundary fluvial incision and lateral erosion, which lead between volcanic (latites or trachybasalts) and to dissection of volcanic rocks covering plastic sedimentary rocks (mudstones and claystones) claystones and mudstones (Fig. 7 L2). Similar (Fig. 9a). The significant role in initiating conception was presented by Yenes et al. landslides is played by fluvial erosion which (2015) on the case of landslides in Duero and leads to dissection of volcanic rocks and Pisuerga valleys. The role of lateral erosion in exposure of sedimentary rocks at the base of landslide development was also emphasised by the slope. Otherwise, when the whole slope e.g. Skempton (1953), Palmquist and Bible consists of volcanic rocks, it is stable and only (1980), Cendrero and Dramis (1996), Azañón small, shallow landslides may occur (Fig. 7 et al. (2005), Lévy et al. (2012) and Wistuba L1). Exposure of sedimentary rocks disturbs (2014). Likewise in the Kamienne Mts, in the slope balance and causes the first event of models devised by aforesaid authors a long- landsliding. Landsliding at the base of slope lasting erosion initiate landsliding. additionally undermines slope stability which In the second scheme established in this causes the landslide to expand upslope in paper landslides develop downslope (Fig. 10). subsequent events of landsliding. As a result It also begins at the boundary between landslide head scarps migrate towards volcanic (trachybasalts) and sedimentary rocks mountain ridge (Figs. 7, 9). Eventually, the (mudstones and claystones), but in the

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

uppermost part of the slope. Landslide trench plastic rocks form a distinctive transverse occurs within rigid trachybasalts at the top of bulge, similar to ridges and depressions mountain ridge (Fig. 10a). Below plastic parallel to slope inclination in the Kamienne claystones and mudstones are deformed and Mts (Fig. 8 B2-B3, Fig. 10 b-c). In addition, in squeezed out (Fig. 10 b-c). The next stage is both schemes subsidence affects the peripheral development and gradual disintegration of a part of a trachybasaltic or sandstone slab. It rocky bench (Fig. 10d). Eventually, short effects with a widening trench and a sliding scarps remain at landslide crown and retreat by rocky bench in the Kamienne Mts or a sagging subsequent slides of colluvial packets. Relief part of a table-topped hill of Mt Szczeliniec of the lower part of the slope becomes Wielki (Migoń et al. 2013). In the lower part of obliterated (Fig. 10e). slopes the rigid rocks are degraded both in the Landslides developing downslopes, which Kamienne Mts and in the aforesaid models are described in literature, are usually vast (Fig. 8 B4, Fig. 10d). This way clearly visible Deep-Seated Landslides – a category of Deep- landslide bodies are formed (Bisci et al. 1996; Seated Gravitational Slope Deformations. Zerathe and Lebourg 2012; Migoń et al. 2013). DSGSDs are often found to completely Further evolution of landslides in the reshape slopes in the high mountain areas and Kamienne Mts involves retreating of the head include many types of mass movements, e.g. scarp by shallow sliding and leads to creating lateral spreading and sagging (Pánek and low scarps (Fig. 8 B5, Fig. 10e). Secondary Klimeš 2016). scarps develop also in models described by Models of landslides expanding Zerathe and Lebourg (2012) and Bisci et al. downslope, which are similar to scheme (1996). developed for the Kamienne Mts, are not In the Kamienne Mts consecutive widely described in literature. This kind of landsliding episodes have been found able to models were described by e.g. Bisci et al. almost completely degrade mountain ridges (1996) in the Marche region in Italy, Zerathe (Fig. 7 L6, Fig. 10e). The potential of and Lebourg (2012) in Maritime Alps and landslides to reshaping topography to this Migoń et al. (2013) for Mt Szczeliniec Wielki extent is emphasized by e.g. Crozier (2010) in the Stołowe Mts. In these schemes and Korup et al. (2010). Analysis of a landsliding starts in the upper part of the slope, geological profile of the study area shows that near the boundary between sedimentary rocks mountain ridges of the Kamienne Mts are with different mechanical properties: cuestas (Fig. 11). The faces of the escarpments sandstones and clays (Bisci et al. 1996), are developed within latites (Włostowa – limestones with mudstones and gypsums Kostrzyna – Suchawa – Waligóra range) or (Zerathe and Lebourg 2012) or sandstones with trachybasalts (Klin – Turzyna – Jeleniec claystones, mudstones and marls (Migoń et al. range). Escarpments are divided by depression 2013). More resistant rocks usually form a cap moulded in mudstones and claystones. The in the uppermost part of the slope, likewise in majority of landslides outlined in the the study area (Bisci et al. 1996; Migoń et al. conducted study have been found on 2013). Then, weak, ductile rocks are squeezed escarpments of cuestas facing northern out under pressure of the overlayer (Migoń et directions (Figs. 3, 11). Only few develop on al. 2013) or outflow (Zerathe and Lebourg the cuesta backslopes, despite more favourable 2012). On the other hand, in the scheme strike of strata. Thus its seems that landsliding proposed by Bisci et al. (1996) the rigid in the study area is a mechanisms of cuesta sandstone slabs float over the underlying clays. escarpment retreat. The role of landslides in In the model by Migoń et al. (2013) squeezed cuestas development is independent of the

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

Fig.11. Cross section of the topography in the study area. The mountain ridges are cuestas developed in latites or trachybasalts divided by valleys developed in sedimentary rocks. Landsliding leads to cuesta faces retreat. direction of landslides extension: upslope or thickness of volcanic rocks in relation to downslope. In both schemes established in this underlying sedimentary rocks. When paper landsliding is a factor significantly sedimentary rocks occur only in the lowest part transforming slopes, leading to degradation of of the slope, landslides develop upslope. When whole mountain ridges in advanced stages of volcanic rocks form only a thin cap in the relief development (Figs. 7-10). uppermost part of the slope landslides develop downslope. In both schemes landsliding leads Conclusions to a significant transformation of slope relief, including degradation of the mountain ridges. - Landsliding is a common phenomenon in the - The mountain ridges of the study area are Kamienne Mts. The major factor promoting cuestas and both described schemes of mass movements in the study area is landslide development can be considered stratigraphical sequence of latites, mechanisms causing retreat of cuesta trachybasalts and tuffs overlying claystones escarpments. and mudstones. Landsliding is initiated near the boundary between volcanic and References sedimentary rocks. - Analysis of geological maps and a high- Azañón J.M., Azor A., Pérez-Peña J.V., Carillo resolution DEM from airborne LiDAR data J.M. (2005) Late Quaternary large-scale allowed to distinguish characteristic types of rotational slides induced by river incision: landslide relief within different types of rocks: The Arroyo de Gor area (Guadix basin, SE latites and trachybasalts. Established types Spain). Geomorphology 69, 152-168, DOI: represents consecutive stages of landslide 10.1016/j.geomorph.2004.12.007 slopes development. Bisci C., Burattini F., Dramis F., Leoperdi S., - Two main schemes of landslide relief Pontoni F., Pontoni F. (1996) The evolution were established: upslope and Sant'Agata Feltria landslide (Marche downslope. In the former landsliding starts at Region, central Italy): a case of recurrent the base of a slope and develops upward. In the earthflow evolving from a deep-seated latter landsliding begins at the top of a gravitational slope deformation. mountain ridge and expands downward. Geomorphology 15, 351-361, DOI: - The direction of relief development depends 10.1016/0169-555X(95)00080-O on the bedrock of a slope, in particular on the

Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

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Contemp.Trends.Geosci., 7(1),2018,1-20 DOI: 10.2478/ctg-2018-0001

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