Open Geosci. 2017; 9:101–113 Research Article Open Access Libor Burian*, Michal Šujan, Miloš Stankoviansky, Jakub Šilhavý, and Ashie Okai Dependence of Gully Networks on Faults and Lineaments Networks, Case Study from Hronska Pahorkatina Hill Land DOI 10.1515/geo-2017-0008 1 Introduction Received August 10, 2015; accepted January 19, 2017 Abstract: In this paper we analyse the dependence be- The process of gully erosion in the area of Central Europe tween gully networks, networks of valleys and faults in the has ceased. There are numerous examples from the past area of Hronska pahorkatina Hill Land. The work is based indicating that the formation of gully network resulted in on the analysis of directions and densities of these three the abandonment of land by farmers. Nowadays, this hap- networks in the study area and subunits of lower hierar- pens rarely due to the ability of man to change the land chical level. The coincidence of all three networks is rare. surface with heavy machinery. At the moment, we have al- This scenario occurs when networks of gullies are situated most no evidence of the formation of new gullies or gully on the bottom of shallow valleys which are conditioned by systems in the area of Central Europe. However, there are the presence of faults. More often scenario is only the co- still numerous examples of the reactivation of this pro- incidence of network of valleys and gullies. The last sce- cess in existing gullies. The process of gully formation ac- nario appears in areas with low fault density. The most tivates secondary processes, which are often more danger- specific scenario is perpendicularity between network of ous than the erosion process itself. For example, the for- gullies and network of gullies. Gullies are situated on steep mation of muddy floods or flash flood is often directly con- slopes of incised valleys in this case. The last scenario ap- nected to areas with permanent gullies. This is one of the pears the most frequently and was also proven by findings reasons why it is necessary to identify and study factors from other studies. We propose three comprehensive ex- influencing formation and reactivation of gullies. planations of the possible dependence between network The exact set of drivers of gullies is still question- of gullies and faults. We also suggest the draft of the pos- able although there is a wide range of hypotheses which sible dependence between network of valleys and gullies. help to identify the majority of these drivers. One uncon- firmed hypothesis assumes the dependence of gully net- works on networks of tectonic faults (dislocations). The verification or falsification of this hypothesis through the analysis of network of gullies, valleys and faults on Hron- ska pahorkatina Hill Land is the primary goal of this paper. This hypothesis was verified mainly through the analysis of distribution of density and directions of networks of gul- *Corresponding Author: Libor Burian: Department of Physical lies, valleys and faults. Geography and Geoecology, Faculty of Natural Sciences, Comenius University, 842 16, Bratislava IV, Slovakia, E-mail: [email protected] Michal Šujan: Department of Geology and Palaeontology, Faculty 2 State of art of Natural Sciences, Comenius University, 842 16, Bratislava IV, Slovakia Miloš Stankoviansky: Department of Physical Geography and The agent of the gully erosion process is the ephemeral Geoecology, Faculty of Natural Sciences, Comenius University, 842 flow of running water [1]. The main cause of gully forma- 16, Bratislava IV, Slovakia tion is too high overland flow, which may be caused by ei- Jakub Šilhavý: Department of Mathematics, Faculty of Applied Sci- ther climatic conditions or alteration in land use. Accord- ences, University of West Bohemia, 301 00, Plzeň, Czech Republic ing to various criteria, it is possible to distinguish valley Ashie Okai: Institute for Ecosystem Research, Group of Ecosys- floor from valley side gullies, continuous and discontinu- tem Research and Archaeology, Christian-Albrechts Universität, Olshausenstrasse 40, D-24098 Kiel, Germany ous gullies, ephemeral and permanent gullies, linear (par- © 2017 Libor Burian et al., published by De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. 102 Ë Libor Burian et al. allel) and dendritic gullies (the last ones occurring mostly tioned determining factors (besides topographical ones, in valley heads) see Fig. 1. there are many artificial linear landscape features) were important also in the formation of historical permanent gullies, which could have originally started as ephemeral gullies. The study of permanent gullies in the Myjava Hill Land, Slovakia, revealed that the majority of gullies linked to linear artificial landscape features typical for the pre-collectivization arable land pattern, mostly to access roads, trails and field boundaries. One of the most curi- ous artificial predispositions for gully formation is plough furrow which has been used as an indicator of cadastral Figure 1: Examples of types of gullies according to: a, position b, boundaries. In several cases, gully position can be linked area of cross-section c, presence of accumulation form d, position to pastures in the original land use mosaic [16]. of other gullies. The abovementioned overview would suggest that gul- lies have been formed only since the beginning of human pressure due to climatic fluctuations and that their spatial The main trigger of the gully erosion process is still un- distribution is controlled by land use pattern and topog- clear. However, it can be assumed that land use changes raphy. However, there are hypotheses that many large gul- and climatic changes are the main triggers [2]. One group lies were formed under forest during the wetter Atlanticum of authors prefers only one of these causes whereas the (7800–5000 BP) [23] or were formed under periglacial con- other group considers both causes as equivalent. More- ditions and were cut into the loess blanket long before over, the influence of land use and climatic changes a protective vegetation cover was established during the is changing in time and space. According to Bučko, Holocene [24], as shown on gullies in the forested area of Mazúrová [3] and Klimaszewski [4], a genesis and evolu- Central Belgium. tion of gullies was associated with extreme rainfall and A different point of view was presented by Knox [25]. sudden snowmelt. The effect of these events was accel- According to his work, at long-time scale, gully develop- erated by a deforestation and agricultural utilization of ment was a complex response to a set of driving factors, a land with deep and soft regolith. An extensive synopsis including tectonic movements. In recent years, some ef- of literature on historical gully erosion is provided in arti- forts have been made to establish a long-term chronology cles by Vanwalleghem et al. [5] and Dotterweich [6, 7]. of gully erosion events for the understanding of both pa- Several stages of evolution of gully networks can be leoenvironmental dynamics and the present-day state of delineated on the basis of land use changes or climatic geomorphic systems under the influence of multiple natu- fluctuations, such as frequently occurring heavy rainfall ral and anthropogenic factors (e.g. [26]). Huang et al. [27] events during the Little Ice Age (LIA) (e.g. [6, 8–12]). There confirmed synchronous down-cutting of gullies and rivers are huge sets of studies suggesting that many permanent over the Loess Plateau, China, which implies that neotec- gullies have been formed since the beginnings of agricul- tonic uplift of the land mass was a major dynamic force ture (e.g. [8, 13–17]). According to Vanwalleghem et al. [5], causing gully incision. According to this study, a gully in- it was confirmed that the majority of gullies studied in Cen- cision occurred when large-scale monsoonal climatic shift tral and north-western Europe were formed between the met with coincided neotectonic uplift; it was dated to ca. 14th and 20th centuriey, with most of them being formed 600 ka, 240 ka, 125 ka and 11.5 ka. in the 20th century, after LIA. However, examples of older In literature coming from the former Czechoslovakia, gullies still exist, e. g. [18, 19]. The oldest gullies in Europe we can find only a handful of works that mention apos- are related to the Neolithic. Schmidtchen and Bork [20] sible relationship between gully formation and tectonics, dated charcoal at the bottom of an infilled gully. Sem- either directly or indirectly. According to Láznička [28], the mel [21] described a Neolithic fossilized gully, though with- creation of a dense network of gullies in the Jihlava River out chronometric dating. valley around Ivančice, Czech Republic, was caused by According to Poesen [22], current ephemeral gullies tectonic movements. He distinguishes younger (historical are formed not only in natural drainage lines (thalwegs and recent) valley side gullies from older (prehistorical) of zero order basins or hollows), but also along linear valley floor gullies which have been formed in glacials and landscape elements (e.g. drill lines, dead furrows, head- interglacials. Harčár [29] states on the basis of research lands, parcel borders, access roads, etc). Most of the men- in the area of NW part of the Low Beskids, Slovakia, that Dependence of Gully Networks on Faults and Lineaments Networks Ë 103 tectonics, together with further geological factors, created primary conditions leading to gully formation. Hrašna and Liščák [30] found out that in the framework of an as- sessment of geodynamic phenomena in the Pokoradzká tabul’a Plateau, Slovakia, the occurrence of gullies is re- lated to the tectonically deteriorated rocks and the orien- tation of gullies coincides with main tectonic directions in this area. In the area of Hronska pahorkatina Hill Land, several authors point to the relationship between tectonics and some topographical erosion linear features, though not gullies.