How does ski infrastructure change soil erosion processes on hillslope?

Ski tourism's popularity is driving a rise in the number of ski resorts. This study aims to present the impact of ski infrastructure on soil erosion processes in the example from a small catchment in the Gubałowskie Foothills in southern Poland, where landscape changes before (since 1879) and after the construction of the ski station (2007) are presented. The analyses of changes in flow accumulation, slope morphometry, and drainage ditches were conducted in the test area. Quantitative analyses were performed using repeated DEMs derived from aerial LiDAR survey and detailed geodetic measurements, complemented by geomorphological mapping done in the field. The study has revealed that the ski infrastructure has not only directly transformed the hillslope by flattening and constructing escarpments (up to 3 m high) but has also created alternating patterns of erosion and accumulation. In the test area, the drainage ditch was poorly designed. It was filled with materials (0.1–0.5 m), and two new outlets formed. The escarpment of the analyzed ski run has been diminished by 0.5 m. An alluvial fan (0.1–0.22 m thick) has developed on the flattened surface below the escarpment with drainage ditch outlets. This fan is eroded by subsurface flow that creates a piping system. The gully below the alluvial fan has retreated upslope, accelerated by subsurface erosion. This study enables the presentation of hillslope adjustments and processes in response to the new conditions caused by ski infrastructure. Such results may support more effective land management in regions changed by ski infrastructure.


| INTRODUCTION
The rapid growth of ski tourism has led to an increase in the number of ski resorts in mountain regions (Candela, 1982;Elsasser & Messerli, 2001;Krzesiwo, 2014Krzesiwo, , 2021;;Vanat, 2022).In the Polish Carpathians, where snowfall is limited and elevation differences are relatively small compared to the Alps, major ski resorts invest in advanced ski infrastructure.Well-operating ski resorts have high-capacity cable cars, comprehensive drainage systems, and advanced methods for preparing and maintaining ski runs (Krzesiwo, 2014;Piątek et al., 2022).It involves hillslope shaping, artificial snowmaking, and regular snow grooming.These activities exert a significant impact on the natural environment (Barni et al., 2007;Keller et al., 2004;Mosimann, 1985;Ries, 1996;Tsuyuzaki, 1994;Wipf et al., 2005).
The most developed ski resorts have ski runs with a suitable gradient.It is achieved by leveling the hillslope, embanking, and creating escarpments which destroy the natural shape of the hillslope (Fidelus-Orzechowska et al., 2018;Krzemień, 1997;Risti c et al., 2012;Ruth-Balaganskaya & Myllynen-Malinen, 2000).The construction and use of a ski run devoid of vegetation cover lead to intensive erosion, which can occur on ski run surfaces and in their surroundings (David et al., 2009;Fidelus-Orzechowska et al., 2018;Furdada et al., 2020;Krzemień, 1997;Wrońska-Wałach et al., 2019).In the case of erosion-prone soils, incisions can exceed 1 m (Fidelus-Orzechowska et al., 2018;Furdada et al., 2020;Krzemień, 1997) and in extreme cases reach several meters (Risti c et al., 2012).Skiing and the use of snow groomers cause soil compaction and the loss of vegetation, which results in soil erosion on ski runs (Barni et al., 2007;Furdada et al., 2020;Krzemień, 1997;Łajczak, 1996;Pintar et al., 2009;Ries, 1996;Risti c et al., 2012;Roux-Fouillet et al., 2011;Ruth-Balaganskaya & Myllynen-Malinen, 2000;Tsuyuzaki, 1994;Wipf et al., 2005).Moreover, the use of snow groomers leads to snow compaction and delays the snow melting season by up to 4 weeks (Keller et al., 2004).It can increase frost and snow processes (e.g., nivation, gelifluction, and frost creep), which may directly cause soil erosion and indirectly increase it by preparing conditions for more intensive water erosion.Artificial snowmaking also extends the duration of snow cover by 30% to 200% compared to the duration of natural snow cover (Bacchiocchi et al., 2019) and increases the volume of water on the hillslope several times (Wrońska-Wałach et al., 2019) creating conditions for increased erosion intensity (Piątek et al., 2022).Moreover, to channelize overland flow with additional water from artificial snow, drainage ditches are constructed on ski runs.The alternation of the natural shape of hillslopes, coupled with the increased volume of water from artificial snowmaking, induces intense erosion and leads to significant changes in the drainage and valley network (David et al., 2009;Risti c et al., 2012;Wrońska-Wałach et al., 2019).
One of the crucial points is the adjustment of geomorphological processes to the new conditions caused by ski infrastructure, such as changes in hillslope shape, the introduction of escarpments, construction of ditches, and the addition of extra water volume from artificial snow.The time of these changes may vary in various environments and under different conditions (Fidelus-Orzechowska et al., 2018;Furdada et al., 2020;Krzemień, 1997;Risti c et al., 2012;Ruth-Balaganskaya & Myllynen-Malinen, 2000;Wrońska-Wałach et al., 2019).
Therefore, the aim of the study is to present the impact of ski infrastructure on soil erosion processes in a small catchment in the Gubałowskie Foothills (pol.Pogórze Gubałowskie), Western Carpathians, in southern Poland, where ski runs were constructed in 2007 and 2011.The detailed aims are: (i) to present landscape changes before and after the establishment of the ski station, (ii) to identify changes in flow accumulation in 2012-2022, (iii) to estimate morphometric changes in the test area where surface and subsurface processes interact, and (iv) to analyze changes in drainage ditches in the test area.Quantitative analyses of landform changes were conducted using repeated DEMs derived from ALS survey and detailed geodetic measurements.This approach allows us to present the adjusting of hillslope and processes, including the occurrence of soil piping, in response to the new conditions caused by ski infrastructure.
This study provides a new insight into the understanding of soil erosion processes changed by ski infrastructure proving for the first time that subsurface processes may emerge in such new conditions, which has not been noted in previous research.

| STUDY AREA
The study was conducted in a small catchment (87.8 ha) located in the Gubałowskie Foothills in the Polish Inner Carpathians, southern Poland (Figure 1).The study area is characterized by high foothills relief (Klimaszewski & Starkel, 1972).The elevation is ranging from 748.9 to 938.4 m above sea level (the highest peak is the Jankulakowski Wierch Mt.À938.4m a.s.l.).The average slope gradient is 14 .Steep slopes, averaging 15.7 , prevail in the NW part of the catchment, while slopes in the SE are more gentle, with an average of 12.2 .The slopes are PIĄTEK and BERNATEK-JAKIEL mainly built of flysch (locally called Podhale-type flysch), with the socalled Upper Zakopiańskie layers dominating in the study area, where sandstones predominate over shales and mudstones (Watycha, 1976).
Steep slopes have been transformed by landslides, so colluvial deposits covers them, while at the foot of gentle slopes remnants of solifluctional covers from the Pleistocene period are found (Watycha, 1976).
The climate is temperate with a mean annual temperature from 4 to 6 C (Obrębska-Starklowa et al., 1995).In the study area, artificial snowmaking is used to maintain ski runs, and the season with artificial snow lasts from November 1 until March 30 under optimal weather conditions (Wrońska-Wałach et al., 2019).The average annual precipitation in 2012-2017 was 886.7 mm, and the water sheet (sourced from the Białka River and a manmade reservoir seen in the southern part of the catchment), used to produce artificial snow on ski runs, ranged from 455.9 to 678 mm.The number of days with snow cover varies from 105 to 175 in areas without artificial snow.
The details of precipitation and amount of artificial snowing are given in Wrońska-Wałach et al. (2019).
The Gubałowskie Foothills experienced significant changes in land use and land cover over the last 40 years (Ciołkosz et al., 2011).
Arable lands have decreased in favor of green areas (grasslands and pastures).Remnants of old agricultural terraces are still visible on the hillslopes in SE part of the catchment (Figure 1b).Forested areas have not undergone meaningful changes.In the study area, forests dominate on steep slopes, while gentle slopes are covered by grasslands (Figure 1c).The main change is the construction of three ski runs which belong to the Kotelnica Białczańska ski resort-one of the largest ski resorts in Poland, with >300,000 visitors per year (Krzesiwo, 2016).The ski runs in the studied catchment were constructed in 2007 (ski runs 1 and 2) and 2011 (ski run 3) (Figure 1b).

| DATA AND METHODS
In order to present the changes in soil erosion processes and adjustment of the system to new conditions caused by ski infrastructure, we collected data on land use and land cover (LULC) changes and elevation, we did fieldwork to obtain the most actual elevation data and we conducted geomorphological mapping.We performed GIS analyses of the obtained data.The details of LULC changes and geomorphological mapping as well as GIS analyses are explained in the following sections.

| Mapping land use and land cover changes and geomorphological features
The information on LULC changes allowed us to present the landscape changes before and after the construction of ski infrastructure.
We concentrated on forested and non-forested (i.e., grasslands and arable lands) areas.These data were obtained from cartographic documents (Table 1).The oldest data are from 1879 and are available from the FORECOM 1 database and the Archives of the Polish Military Geographical Institute (pol. Wojskowy Instytut Geograficzny, WIG, 1919-1939).The interpretation of these historical data, particularly forest cover, was based on work done within the FORECOM project (Kaim et al., 2016;Kozak et al., 2018;Ostafin et al., 2017).The most recent data, that is, orthophotos, were acquired from the Head Office of Geodesy and Cartography (pol.Główny Urząd Geodezji i Kartografii,

GUGiK).
In order to analyze soil erosion processes and their evidences in the field, geomorphological mapping was conducted.All soil pipingrelated forms and features, that is, piping sinkholes and pipe outlets (Figure 2), were mapped.Their size (length, width, and depth) was measured with an accuracy of 0.01 m using a measuring tape.

| Digital elevation models and GIS analyses
To analyze landscape changes, including soil erosion processes in the catchment changed by the ski infrastructure, two sets of point clouds obtained via two ALS surveys were used, along with the grid of points measured in the field using the electronic total station.The first point cloud (data acquisition 2012) was acquired from the Head Office of Geodesy and Cartography in Poland (pol.GUGiK).The 2012 ALS was carried out using a RIEGL LMS-Q680i scanner with a density of 4 to 6 points per m 2 and pulse repetition frequencies of 300 kHz (Table 2).
The second point cloud (data acquisition 2016) was obtained from the Kotelnica Białczańska Company.It was created by the ProGea4d company (Warchoł, 2017;www.progea4d.pl).RIEGL VQ-580 scanner with a density of 50 points per m 2 , and pulse repetition frequencies of 380 kHz (Table 2).Both point clouds (2012 and 2016) were classified T A B L E 1 Cartographic documents used in the study to infer about land use and land cover changes.Then, this grid of points was interpolated using the Kriging tool using ArcGIS Pro software to obtain a DEM with a horizontal resolution of 1 Â 1 m and a vertical resolution of 0.03 m (Table 2).Next, all DEMs The LULC changes due to ski infrastructure began in 2007 with the construction of ski runs 1 and 2 (Figures 1b and 3d).The last ski run (ski run 3) was built in 2011.Ski run 1 is 460 m long and 55 m wide, ski run 2 is 390 m long and 35 m wide, while ski run 3 is 1040 m long and 75 wide (Figure 1b).Drainage ditches have been constructed on each ski run to direct surface runoff away from the ski runs (Figure 1b).Moreover, there is a ski run link connecting ski run 3 with the ski run outside the studied catchment (Figure 1b).This ski run link serves as a ground road during the winter off-season.
T A B L E 2 Sources and resolution parameters of used DEMs.The construction of ski runs required ground leveling, eading to the creation of escarpments up to 3 m high in the case of ski run 3.
In the test area (Figure 1b), the alluvial fan formed below the drainage ditch and above the gully (Figure 1b,d), which is seen on the DoD as the accumulation zone (Figure 4b).Thirty piping sinkholes were mapped in the test area (Figures 2 and 4).Their depth indicates the depth of soil pipe formation.They formed at a mean depth of 0.16 m with a minimum depth of 0.05 m and a maximum depth of 0.39 m (standard deviation is 0.08 m).The pipe outlet (0.17 m) is located in the gully head below the alluvial fan (Figure 2d).

| Flow accumulation changes
In the test area (Figure 1b), flow accumulation analyses for 2012 and 2016 indicate a significant change in erosion on ski run 3 and its surroundings.In 2012, only a small portion of the flow from the area above ski run 3 was drained via a ditch to the gully (Figure 5a).From 2012 to 2016, erosion processes in the test area of ski run 3, particularly in its central and southern parts, resulted in the redirection of flow, and the drainage area doubled (Figure 5b).The catchment area of the tested gully increased from 9614 m 2 in 2012 to 20,689 m 2 in 2016.

| DEM of difference analyses
The DoD analysis of the surroundings of ski run 3 for 2012-2016 indicates significant changes in elevation that occurred during the 4 years of operation of this ski run.The most significant lowering of the escarpment of ski run 3 exceeds 0.5 m ± 0.048 m (Figure 6).However, the most crucial change is the rise of the ground level in the drainage ditch, which was filled with materials from the higher parts of the ski run (Figure 6).This filling varies from a minimum of 0.1 m ± 0.048 m to even more than 0.5 m ± 0.048 m at the boundary of the ski run 3 area (Figure 6).Moreover, one can observe the lowering of the ground level in the alternative drainage line.Below the escarpment of ski run 3, the rise in ground level indicates accumulation in the alluvial fan area.The upward elevation here ranges from 0.1 to 0.22 ± 0.048 m in an area of about 360 m 2 (Figure 6).
The consequence of changes in flow directions (the increase in the accumulation flow area of the gully, Figure 5) was the intensification of erosion in the gully below the alluvial fan.This is evidenced by a decrease in elevation at the gully headcut (values exceeding 0.5 ± 0.048 m, with a maximum of 1.3 ± 0.048 m), and just below the accumulation of this eroded material is observed (Figures 6 and 7).
The alluvial fan has grown in the subsequent period, from 2016 to 2022 up to 0.31 ± 0.051 m, especially in the central part (Figure 7).The retreat of the gully headcut below the fan has progressed, and the erosion from 2016 to 2022 exceeded 1 ± 0.051 m (Figure 7).The main change that occurred in this period compared to the previous one is the start of backward erosion of the gully also in the SE direction (previously the SW direction was dominant).The lowering here reached from 0.3 to 0.41 ± 0.051 m.The second significant change is the increase in ground level in the southern part of the alluvial fan, up to 15 cm.This part was generally eroded in the previous period, that is, 2012-2016.

| Changes in drainage ditches
Drainage ditch 1 was constructed as part of the ski run 3 infrastructure in 2011.The DoD analysis suggests that drainage ditch 1 has been filled over the period 2012-2016.During this period, drainage ditch 2 was naturally created by water flow adjusting to the water generated naturally and due to snow melting from artificial snow (Figure 8d).The orthophoto from 2015 shows both drainage ditches (Figure 8a).Before 2018, erosion had occurred between ditches 1 and 2, and drainage ditch 3 had formed (Figure 8b).By 2022, drainage ditch 3 had deepened, and ditches 1 and 2 had filled in (Figure 8c).This is indicated by Figure 8e, which shows that there is erosion below the outlet of drainage ditch 3 and a shallow channel has formed.The outlets of drainage ditches 1 and 2 (on the escarpment of ski run 3) are suspended, and accumulation is occurring there (Figure 8e), which is clearly visible on the DoD (Figure 8d).

| Erosion and accumulation processes on the hillslope changed by ski infrastructure
The presented results allow us to reconstruct the adjustment of the hillslope to the new conditions resulting from the ski infrastructure.snowmaking results in a significant increase in snow cover and the water supplied to the hillslope (Bacchiocchi et al., 2019;Wrońska-Wałach et al., 2019).This leads to a significant acceleration of the geomorphological processes compared to the surrounding areas.
An earlier study in the same ski resort showed that artificial snowmaking causes an almost threefold increase in the volume of water on the hillslope compared to the condition with only natural precipitation (Wrońska-Wałach et al., 2019).The construction of ski run 3 (Figure 1b) and changes in water volume had already resulted in erosion below ditch 1 before 2012 (Figure 8) and accumulation in the lower section, leading to the formation of the alluvial fan.Analyses of landscape changes revealed that before the construction of ski run 3, the alluvial fan in the test area did not exist.The slope at this location was used as arable land (Figure 3a-c), with agricultural terraces (Figure 1b).The material accumulated in the alluvial fan originated from the erosion of the surface of ski run 3 and the ski run escarpment.This material could have been easily moved due to the short time since the ski run construction (poor soil compaction) and the lack of vegetation cover (Figure 8a).
The DoD analysis shows that ditch 1 was naturally filled between 2012 and 2016 (Figure 6).This suggests a poorly designed ditch routing, unsuited to the changed environmental conditions.The adaptation of the gradient of ski run 3 to the new volume of water and new drainage patterns led to the erosion of an alternative route-ditch 2 (Figure 8), which also began to fill in on the escarpment of ski run 3 between 2012 and 2016 (Figure 6).The formation of ditch 2 resulted in an increase in the catchment area of the gully in the test area (Figure 5).Between 2012 and 2016, the alluvial fan was accumulating in its lower part and eroding in its upper part (Figure 7).The increase in the catchment area (Figure 5), and volume of water drained by ditch 2, and the adaptation of the entire ski run 3 surface over time (lowering of the ski run surface and escarpment) to the new drainage patterns led to the formation of ditch 3 between 2016 and 2018, which now drains the ski run in this area (Figure 8b,c,e).The acceleration of erosion since 2016 in ski run 3 can also be explained by the increased accumulation in the central and eastern part of the alluvial fan (increased accumulation by accelerated erosion above) and increased erosion in the gully in the test area (Figure 7).
It is worth noting that the western part of the fan has been decreasing since 2016, having previously been elevated (Figure 7).
This change is associated with subsurface erosion by soil piping.In this area, thirty piping sinkholes have been mapped (Table 1, Figures 2   and 4).This suggests that the formation of the alluvial fan and the escarpment of ski run 3, along with increased water volume (from artificial snow), resulted in changes in flow.Some part of the surface runoff has been transformed into subsurface flow.This was possible because of the construction of an escarpment that has led to an increase in the hydraulic gradient.This gives a similar effect as agricultural terraces, the existence of which favors pipe development (Romero Díaz et al., 2007;Tarolli et al., 2014;Watts, 1991).Moreover, in this area, Cambisols developed in flysch dominate, which under specific conditions might be susceptible to soil piping, as already noted in other parts of the Carpathians (Bernatek-Jakiel et al., 2016).This implies that the ski infrastructure resulted in the occurrence of soil piping and, thus, piping-related forms and features that were not observed there before.
This study has shown that the adjustment of geomorphological processes to the new conditions caused by ski infrastructure needs several years, although the largest landscape changes occurred in the first years after the construction of ski resort.The parts of hillslopes were levelled, escarpments and drainage ditches were constructed (Figures 1 and 3).Moreover, the entire catchment has to be adjusted to the additional extra water volume from artificial snow.In the next years when ski resort operates, the escarpments below drainage ditches are eroded and the alluvial fans develop on the more gentle slope.In the study, area soil piping processes emerged due to the specific conditions (especially the increase of hydraulic gradient).Since now, some authors have emphasized that the most significant changes occur in the first years following the construction of ski runs and the accompanying infrastructure (Fidelus-Orzechowska et al., 2018;Risti c et al., 2012;Ruth-Balaganskaya & Myllynen-Malinen, 2000), while others have indicated that the adjustment of system persists for several years (Furdada et al., 2020;Krzemień, 1997;  et al., 2019).This study has proved that the adjustment is the ongoing process, especially when it appeared that one drainage ditch has been improperly constructed.
In this study, the course of drainage ditches has proved to be crucial in intensifying erosion and accumulation.Research conducted in a neighboring catchment and at the same ski resort showed that several metres below the outlets of the drainage ditches, both erosion and accumulation occurred within the first 2 years after the construction of a ski run (Wrońska-Wałach et al., 2019).Within the following 2 years, erosion occurred below the drainage ditch in most cases (Wrońska-Wałach et al., 2019).In this study, the accumulation zone occurred about 80-100 m below the drainage ditch, and only surface soil erosion processes were recorded directly at the ditch outlet during the entire study period of 11 years.Accumulation occurring at a greater distance from the drainage ditches and even in the valley network was also observed in Mont Dore, France (Krzemień, 1997), and Colorado, US (David et al., 2009).In this study, similarly to the work carried out in the Pyrenees (Furdada et al., 2020) The detailed study was conducted in the test area (Figure1b,d), representing the hillslope changed by ski run 3 and the area below the ski run (Figure1d).The test area consists of the gully that developed below the drainage ditch constructed in ski run 3 and the associated fan.Similar sites with gullies and fans developed below the drainage ditches are common in the study area and in the surrounding catchments.Field recognition done before the detailed study allowed us to select the test area that represents the part of hillslope changed by ski run and drainage ditch, where additionally the changes in drainage ditches outlets have occurred.In the test area, we conducted fieldwork and analyzed the DEMs of Difference.

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I G U R E 1 Location of the study area: (a) a regional overview, (b) a hillshaded relief (2012) of the catchment with geomorphic features and ski infrastructure marked, (c) a photograph of the catchment with ski run 3, (d) the test area with an alluvial fan marked (photos: A. Bernatek-Jakiel).[Colour figure can be viewed at wileyonlinelibrary.com] -89-C-c-4-1, M-34-89-C-c-2-3 F I G U R E 2 Soil piping-related forms and features: (a-c) piping sinkholes, (d) a pipe outlet in the gully head (photos: A. Bernatek-Jakiel).[Colour figure can be viewed at wileyonlinelibrary.com] by the data provider according to the American Society for Photogrammetry and Remote Sensing (ASPRS) standard (ASPRS, 2008).These point clouds were used to generate DEMs.Each DEMs were built on the basis of the value of class 2 (ground) points and acquired with a horizontal resolution of 1 Â 1 m.Moreover, detailed geodetic measurements using the electronic total station (Topcon Hiper II, with 0.03 m vertical accuracy) was done in June 2022 in the test area(Figure 1b,d)  in order to gain the most actual elevation data.A grid of points was done, that is, points were made every meter in the test area, covering the fan (Figure1b,d).

(
photo from 2003 (Figure3c).The area of forest increased to 39.6 ha (45.1% of the catchment area) in 2001, and in 2003 forests covered 41.7 ha (47.4%).Few years after the construction of ski runs (2022), the area of forest decreased to 35.3 ha (40.1% of the catchment area).

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I G U R E 3 Land use and land cover changes in the study area from 1879 to 2022.The red rectangle indicates the study site used for detailed analysis: (a) 1879, (b) 2001, (c) 2003, (d) 2022.[Colour figure can be viewed at wileyonlinelibrary.com]

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I G U R E 4 Soil piping sinkholes mapped in the field differentiated by their depth marked on: (a) the orthophoto (2022), (b) on the DEM of difference (DoD) 2016-2022, where soil piping sinkholes are visible in the erosion zones and near the accumulation zone, that is, the alluvial fan (marked with a white dashed line on [a] and a lemon dashed line on [b]).Background: ortophoto from 2022.[Colour figure can be viewed at wileyonlinelibrary.com] Ski run surfaces are subject to erosion and accumulation from the moment of construction (Fidelus-Orzechowska et al., 2018; Risti c et al., 2012).Ski run 3 was built in 2011 and has been used for skiing since then.The maintenance of the ski infrastructure through artificial

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I G U R E 5 The catchments of the test area and drainage lines generated using flow accumulation calculations: (a) in 2012, (background: hillshade from 2012), (b) in 2016 (background: hillshade from 2016).[Colour figure can be viewed at wileyonlinelibrary.com]

6
The DEM of difference (DoD) from 2012 to 2016 in the test area (marked in Figure 1b), background: hillshade from 2016.The photo presents the area of the alluvial fan below the escarpment of ski run 3 (Photo: D. Piątek).[Colour figure can be viewed at wileyonlinelibrary.com]F I G U R E 7 The DEM of difference (DoD) prepared in the test area with the alluvial fan marked on Figure 1b: (a) 2012-2016, background: ortophoto from 2015, (b) 2016-2022, background: ortophoto from 2022.[Colour figure can be viewed at wileyonlinelibrary.com]F I G U R E 8 Changes in drainage ditches above the test area (Figure 1b) on the escarpment of ski run 3: (a) drainage ditches in 2015, (b) in 2018, (c) 2022, where 1the drainage ditch constructed as part of the ski infrastructure, 2 and 3the drainage ditches formed naturally by water flow adjusting to the water flow generated naturally and due to snow melting from artificial snow, (d) drainage ditches 1 and 2 marked on the DEM of difference from 2012 to 2016, background: ortophoto from 2022, (e) drainage ditches 1, 2 and 3 on the escarpment seen in the photo (photo: D. Piątek).[Colour figure can be viewed at wileyonlinelibrary.com]Wrońska-Wałach , there are alternating zones of erosion and accumulation in the surroundings of drainage ditches.A study in a neighboring catchment also identified changes in drainage pattern(Wrońska-  Wałach et al., 2019).However,Wrońska-Wałach et al. (2019)  underlined that the greatest changes occurred in a short period after the construction of a ski run.This study has shown evidence of changes in flow accumulation and the area of the catchment due to processes of accumulation and the creation of new drainage ditches that may occur several years after ski run construction as a result of the adjusting hillslope to the new conditions.6| CONCLUSIONSThe detailed analysis of historical cartographic data (since 1879), DEMs from 2012, 2016, and 2022, along with geomorphological mapping in the field has allowed us to reconstruct the adjustment of the system to the new conditions caused by ski infrastructure, including the addition of extra water volume from artificial snow.We have been able to present changes in soil erosion processes on the hillslope after the construction of ski runs (leveling of slopes), introduction of escarpments, construction of drainage ditches. in a small catchment in southern Poland.The ski infrastructure in the study area consists of ski runs, escarpments, and drainage ditches.Additionally, the operation of the ski resort involves artificial snowmaking, resulting in an increased volume of water in the catchment compared to natural conditions.The study has revealed that the ski infrastructure has not only directly altered the hillslope by leveling it and creating escarpments (up to 3 m high) but has also influenced the activity of processes.Alternating erosion and accumulation processes have been observed, as well as the emergence of a new process-soil piping has been identified.The detailed study was conducted in the test area with ski run 3 constructed in 2011.The designed ditch turned out to be poorly designed, as by 2022, two new outlets of the ditch had formed, indicating the adaptation of hillslope to the altered conditions brought about by the new slope shape, escarpment and increased water volume.The changes in the ditch outlet have been related to the increased water volume (from artificial snow).The initial flow accumulation area of the constructed ditch expanded from 9614 m 2 in 2012 to 20,689 m 2 in 2016.By 2016, the escarpment of the analyzed ski run had been diminished by 0.5 m, and the constructed ditch had been filled by materials ranging from 0.1 m and to over 0.5 m thick.The alluvial fan, with a thickness varying from 0.1 to 0.22 m, developed on the flattened surface below the escarpment with drainage ditch outlets.This fan is still accumulated in the lower part, while in the side part, it is eroded by subsurface flow, creating a piping system at a mean depth of 0.16 m (with a maximum of 0.39 m).The gully below the alluvial fan (that existed before the ski run construction) has retreated upslope, which is accelerated by subsurface processes.The recognition of soil erosion processes on hillslopes altered by human impact is crucial for a better understanding of sediment and flow connectivity at the catchment scale.It also shows the adjustment of the system to new conditions, which is an important step toward more effective land management in regions changed by ski infrastructure.ACKNOWLEDGMENTSThis publication is part of a project that has received funding from the Horizon 2020 Framework Programme under grant agreement No 952327.The research for this publication has been also supported by a grant from the Priority Research Area Anthropocene under the Strategic Programme Excellence Initiative at Jagiellonian University and the publication has been supported by a grant from the Faculty