Case Study Experiment - Mitigating muddy floods and soil erosion
The researchers in Slovakia conducted three eperiments 1) tested the effect of rainfall intensity, soil moisture and vegetation cover on generation of overland flow and sediment transport; 2) measurements of gully erosion; and 3) measurements of sediment loads and bed sediments in a small water reservoir.
|Mitigating muddy floods and gully erosion|
|1. Generation of surface runoff||
|2. Changes in erosion gully||
|3. Changes in sediment loads||
Further details about the experiment on the generation of runoff can be found in the fact sheet HERE(SK), changes in erosion gully fact sheet HERE (SK) and changes in sediment loads HERE (SK) and in the project report HERE.
Michaela Danáčová, Radovan Nosko, Roman Výleta, Beata Randusová, Ján Szolgay (2015) Possibilities of estimating the gully erosion changes on the Myjava Basin Published in: ACTA HYDROLOGICA SLOVACA Ročník 16, Tematické číslo 1, 2015, 167 - 175
Korbeľová, Lenka, and Silvia Kohnová (2017) Methods for Improvement of the Ecosystem Services of Soil by Sustainable Land Management in the Myjava River Basin Published in: Slovak Journal of Civil Engineering 25, no. 1, 2017, 29-36 https://doi.org/10.1515/sjce-2017-0005
Čistý, M., Čelár, Ľ., Minarič, P. (2015) Conversion Between Soil Texture Classification Systems Using the Random Forest Algorithm, Air, Soil and Water Research. Published in: Air, Soil and Water Research. Volume 8, Pages 67-75, ISSN 1178-6221 http://www.la-press.com/conversion-between-soil-texture-classification-systems-using-the-rando-article-a5217
The pilot catchment is situated in the Myjava Hill Land. This has an area of 645 km2 and it is a down-faulted zone between the flysh massif of the White Carpathians and the limestone–dolomite horst of the Little Carpathians. Its character is mostly plateau-like with relief oscillations of the order of 40-130 m. Senonian, Paleogene and Neogene sedimentary rocks of medium to low resistance, covered by a thick mantle of regolith, and locally also by beds of loess and loess loams, dominate the local geology. Loamy cambisols and luvisols are the predominant soil types. Erosion has resulted in a clayey-loam to loamy diluvium, which is often 10-15 m thick. The thickest beds of this material are situated on the foothills and in the bottoms of dells and dry valleys. The mean annual precipitation is 650-700 mm with natural vegetation predominantly oak forests and beech forests in the highest parts covering the area. At present, arable land occupies 55% of the Myjava Hill Land, the additional 13% represent heterogeneous agricultural areas. The Myjava River drains waters from the Biele Karpaty (spring area) and Malé Karpaty mountains (White Carpathians and Little Carpathians). The catchment contains the Myjavská pahorkatina (Myjava Hill Land) and Borská nížina (lowland area). The highest point in the catchment is Čupec hill with an altitude of 819 m, with the lowest point at the confluence with the Morava River at 149 m a.s.l.
Main soil threat
The Myjava Hill Land is known for its quick runoff response and related muddy floods, determined by both natural and socio-economic conditions. The present-day cultural landscape of the Myjava Hills is the result of ~600-year anthropogenic transformation of the naturally forested landscape. There are major stages in man-made interventions in the area including the medieval kopanitse colonization (formation of patchy small rural settlements, deforestation and radical creation of agricultural fields), the socialist collectivization of agriculture after 1949, and the socio-economic changes (de-collectivization of agriculture) after 1989. Socio-economic changes after 1989 did not result in significant change in land use pattern to date. A dense network of dry valleys concentrate runoff resulting in ephemeral gullying and the generation of muddy floods. Water flowing from agricultural fields is carrying large quantities of soil as suspended sediment or bed load. The flooding with a high concentration of eroded material is generating muddy deposits. These processes represent a significant environmental and natural hazard in the conditions of the Myjava region.
Other soil threats
Deforestation and agricultural cultivation on extensive areas has caused enormous intensification of the originally natural landscape-forming processes and tillage erosion. The combination of adverse hydrological conditions, such as impervious subsoils, frozen subsoil and changes in extreme precipitation, has led to the development of gullies. These processes increase the slow and harmful geomorphic changes, leading to erosion from tillage and gullies.
Location and Digital Elevation Model (DEM) of the Myjava basin (right) in Slovakia (left) and the Myjava River network (Source: SRTM)
Geology and soils
The geological structure of the Myjava basin is not homogeneous and is characterized by complicated tectonics and geology - below. The Myjava Hills highlands and Chvojnica Hills highlands, which are situated in the upper part of the catchment, belong to the flysch belt of the subregion of the Outer Carpathians. They are mainly formed by sandstone, sandy claystones, claystones and fine conglomerates. Upstream of the River Myjava near the town of Myjava, even calcareous sandstones and limestones can be found. The eastern part of the catchment also contains some areas with dolomites, marls and conglomerates. However, the biggest part of the basin is formed by gray and varied siltstones and claystones covering approximately 30% of the area. The rest of the catchment, which lies in the lowlands situated in its western part, is predominantly formed by calcareous clays, silt and gravel.
Soil groups and materials (WRB) (left) and Land Use in the Case Study (Source: JRC) (right).
The spatial variability of the soil in the catchment is mainly given by the substrate and terrain. The upper parts of the catchment with higher inclinations of the relief are mostly comprised of Cambisols which are patchily mixed with Calcaric Cambisols (above). The area around the town of Senica is formed by Haplic Luvisols and the vicinity of the River Myjava is formed by Fluvisols and light Arenosols, which are represented mainly by sandy soils. The structure of the soil in most of the basin is predominantly loamy with some sandy soil in its southwestern part. The permeability of the soils is predominantly medium with some areas around the confluence of the River Myjava and River Morava having high values and a small area around the town of Myjava having slightly lower values. On the larger part of the catchment, the soil reaction defining the pH of the soils is slightly alkaline to neutral with the pH in a range of 6.5 to 8. Only the areas in the southern part of the catchment with coniferous vegetation have extremely acid soil with a pH around 4.5-5.5. The soil moisture regime of this soil ranges from slightly moist (the northern part) to slightly dry (the southern part).
The present-day appearance of most of the landscape in the Myjava Hills highlands has resulted from approximately seven centuries of human activity (Stankoviansky, 1997). The natural landscape lasted almost to the end of the 13th century, when the two medieval castles of Čachtice and Branč were constructed and initiated more significant settlement of this area. The original vegetation of the catchment, which was predominantly formed by oak and beech forests in its highest parts and grasslands in the lower parts, was gradually replaced by pastures and agricultural land. The wetlands lying in the lower parts of the catchments in the vicinity of the river were dried, and the land was reclaimed in favour of pastures and fields. The growing population resulted in the hereditary division of existing fields into ever smaller plots, which became increasingly narrow because they were divided longitudinally. These plots were predominantly tilled along the contour lines and less often perpendicular to them. This led to a dense network of artificial linear landscape elements such as field boundaries, banks, lynchets, headlands, access roads, paths and drainage furrows. After the Second World War, the kopanitse landscape changed because of the collectivization of agriculture under the new communist regime. Collectivization resulted in the merging of the former small private plots into large cooperative fields, the removal of the dense network of artificial linear landscape elements, and the levelling of the terraces that had been created by long-term contour tillage.
Nowadays the biggest part of the catchment is covered by arable land that accounts for almost 50% of the territory. Most of the arable land is situated on the right bank of the River Myjava. The northern part of the catchment is still covered by the original heterogeneous agricultural areas, which are comprised of small plots of agricultural land which were not significantly affected by the communist collectivization. This part of the catchment lies in the foothills of the Myjava Hills highlands and thus contains a small percentage of meadows and pastures. Most of the lowlands which are situated on the left bank of the River Myjava in the southern part of the catchment are covered by coniferous and mixed forests which are supplemented by shrubs and natural meadows. The total amount of afforested land in the catchment is 17%. Artificial surfaces, such as urban, industrial or transportation sites, constitute less than 1% of the total area of the catchment with the biggest settlements in the vicinity of River Myjava and its main tributaries. The land use map is shown above.
Most of the catchment of the Myjava River lies in a warm region with 50 or more “summer days” (i.e. a day with a maximum temperature 25oC) per year on average. This region is characterized by a moderately humid climate with mild winters, i.e. the mean temperature in January is higher than -3 oC. A small percentage of the catchment with a higher altitude (the northern part of the catchment) lies in a moderately warm region with less than 50 “summer days” per year, and mean temperatures of 16 oC in July. This heterogeneity is a result of the hilly character of the northern and eastern parts of the catchment. The catchment lies in a region with mean annual sums of global radiation around 1200 kWh/m2. The mean annual potential evapotranspiration totals are in an interval between 500 and 700 mm. Rainfall data from 16 gauges dating since 1981 are used to calculate the areal precipitation amounts, the inter-annual regime of which is shown below. It demonstrates that the driest months are January and February with only 40 mm of total precipitation on average. On the other hand, the months with the highest average precipitation rates are the summer months of June and July with over 70 mm of precipitation.
(a) Average annual and (b) mean monthly precipitation and temperature at Myjava basin for the period 1981-2008.
Precipitation from the available records shows no significant trend (see Figure 10.3) and remains stable at an annual rate of 634 mm. The mean monthly air temperature over the catchment is shown above. The lowest air temperatures can be observed in winter months with January being the coldest month with an average air temperature of -1.5oC. The lowest observed mean air temperature over the catchment in the period between 1981 and 2008 was -21.9oC. The warmest months are July and August with average air temperatures around 19oC (the maximum mean air temperature over the catchment was 29oC).
The catchment contains the Myjavská pahorkatina (Myjava Hills highlands) and the Borská nížina (lowland area). The highest point in the catchment is Čupec Hill with an altitude of 819 m a.s.l., while the lowest point is at its confluence with the Morava River at 149 m a.s.l.
Drivers and Pressures
The driving forces/pressures for flooding and landslides are of natural, social, economic, and ecological origins. They interact in complex ways; therefore, the analysis of their impacts requires respecting synergies (Crozier, 2010). Natural drivers include impervious subsoils, frozen subsoil and changes in extreme precipitation. There are major stages in man-made interventions in the area, including the medieval kopanitse colonization (formation of patchy, small rural settlements, deforestation and the radical creation of agricultural fields), the socialist collectivization of agriculture after 1949, and the socio-economic changes (de-collectivization of agriculture) after 1989. Deforestation and agricultural cultivation have caused an enormous intensification of the originally natural landscape-forming processes and erosion due to tillage. The socio-economic changes after 1989 have not resulted in significant changes in the land use pattern to date. A dense network of dry valleys concentrate the runoff, which results in ephemeral gullying and the generation of muddy floods. Water flowing from agricultural fields is carrying large quantities of soil as suspended sediment or bed load.
European and national policies targeting flooding/landslides provide a broad interlinked framework for mainstreaming flooding and landslide risk management mainly through agriculture, water and climate change mitigation policies. At EU level a comprehensive set of policies addressing such risks exists, which are implemented into national policies/legal frameworks. The most relevant in the EU are the EU Water Framework Directive (WFD), the EU Floods Directive (FD), the EU Common Agricultural Policy (CAP) and Structural and Cohesion Funds. The WFD recommends to take climate change into account in River Basin Management Plans and FD requires flood risk management plans and flood risk assessments. While the CAP does not directly address flood and landslide risks, its recent reforms present mainstreaming opportunities through cross-compliance regulations that require on-farm measures (e.g. small retention ponds, shelter belts which can reduce runoff and changes in tillage practices to maintain soil moisture). The Agri-Environment Program plans to compensate farmers for implementing on-farm water-retention and other ecological investments with indirect impacts on flooding and landslides. The European Commission also stresses the need of mainstreaming climate change mitigation into flood/landslide risk policy. A Blueprint to Safeguard Europe’s Water Resources stressed the importance of natural water retention measures and planned policy integration tools for the 2014–2020 Multiannual Financial Framework (MFF) that could greatly enhance the take-up of green infrastructure. However, lacking a European Soil Framework Directive, soil conservation policies have been in the past, and still usually are, developed on a national or local basis. For this reason, assessments of their effects on flooding and landslides are difficult to be found in literature. Despite the implementation of the EU Flood Directive, the focus on flood protection and integrated water resources management is not yet fully operational. Measures that aim at flood protection in forested or agricultural areas seem to lack economic and legal support and incentives.
Status of soil threats
Erosion has resulted in a clayey-loam to loamy diluvium, which is often 10-15 m thick. The thickest beds of this material are situated on the foothills and in the bottoms of dells and dry valleys. The main sources of the soil threats are floods, soil erosion by water, and muddy floods. Water flowing from agricultural fields is carrying large quantities of soil as suspended sediment or bed load (see below). Flooding with a high concentration of eroded material is generating muddy deposits. These processes represent significant environmental and natural hazards in the conditions of the region. Among other sources of soil threats are deforestation and agricultural cultivation on extensive areas, which has caused an enormous intensification of the original natural landscape-forming processes and erosion from tillage. The combination of adverse hydrologic conditions, such as impervious subsoils, frozen subsoil, and changes in extreme precipitation, has led to development of gullies. These processes increase the slow and harmful geomorphic changes, leading to erosion from tillage and gullies, and increasing the risk of flash floods. Maps of the main sources of the soil threats are shown below.
An example of muddy sediment deposited in the catchment during an extreme rainfall event
Maps of various sources of soil threats
Maps on the current state of land use, soil degradation and soil conservation in the case study area have been produced using the WOCAT (World Overview of Conservation Approaches and Technologies) methodology
The steps of this process are as follows:
1) The area to be mapped is divided into distinctive land use systems (LUS). 2) The team gathers the necessary data on soil degradation and conservation for each LUS using a standardised questionnaire, in close consultation with local land users, and supported where possible by remote sensing or field data. 3) For each LUS, the soil degradation type, extent, degree, impact on ecosystem services, direct and indirect causes of degradation, as well as all soil conservation practices, are determined. 4) Once collected, the data is entered in the on-line WOCAT-QM Mapping Database from which various maps can be generated.
Following the principles of all WOCAT questionnaires, the collected data are largely qualitative, based on expert opinion and consultation of land users. This allows a rapid and broad spatial assessment of soil degradation and conservation/SLM, including information on the causes and impacts of degradation and soil conservation on ecosystem services.
More details about the methodology used to produce these maps and their interpretation can be found here.
Land Use (click on maps to expand)
The degree of degradation reflects the intensity of the degradation process, whilst the rate of degradation indicates the trend of degradation over a recent period of time (approximately 10 years).
The "effectiveness" of conservation is defined in terms of how much it reduces the degree of degradation, or how well it is preventing degradation. The Effectiveness trend indicates whether over time a technology has increased in effectiveness.
Effects of soil threat on soil functions
Table below summarises and ranks the effects of floods on the soil functions of Myjava.
|Functions of soil||Explanation||Effect|
|Biomass production||Loss of agricultural and food production||M|
|Storing, filtering and transforming nutrients, substances and water||Decrease in retention and infiltration capacity of soil||M|
|Gene reservoir/ Biodiversity pool||N|
|Physical and cultural heritage||
Damages of cultural heritages
|Physical medium||Destruction of infrastructure (roads, railroads)||H|
|Source of raw materials||Transport of raw material/ collection on inundated areas||H|
Administrative and socio-economic setting
The Myjava River Basin consists of Myjava, Senica, Malacky and Skalica Districts (NUTS4). They belong to the Trenčín Region (Trenčiansky, NUTS3) and the Trnava Region (Trnavský, NUTS3) of Western Slovakia.
Slovakia continues to implement measures under the Sectorial Operational Programs Protection of the Environment and Agriculture and Rural Development. Efforts in rural development have aimed at increasing the competitiveness and value of the environment and the countryside as well as the quality of life in rural areas. The basic legislative frameworks are the Council Regulation (EC) No. 1698/2005 on support for rural development by the European Agricultural Fund for Rural Development, Community strategic guidelines for rural development, the National strategy plan for rural development of the Slovak Republic. With respect to the environment, the National Biological Strategy of Slovakia, National strategy of sustainable development, the EU Water Framework Directive and the River basin management plans and the Directive 2007/60/EC on the assessment and management of flood risks and the relevant Slovak legislature, control the institutional and local planning and development.
Population of Trenčiansky Region and GDP per capita trends for Slovakia and the Euro Area
Management options can be individually tailored to stakeholders in order to be able to secure: a) mitigation of the effects of muddy floods and landslides, b) maintenance of the current state of agricultural production, c) preservation of the so-called “kopanitse” landscape for further development of tourism and d) preservation of the current state of flora and fauna in the region.
Relevant end-users and local stakeholder groups include;
- The Ministry of the Environment of the Slovak Republic
- The Ministry of Agriculture and Rural Development
- Slovak Environmental Agency
- State Nature Conservancy of the Slovak Republic
- The Water Research Institute (responsible for the EU Water Framework Directive and River basin management plans)
- The Slovak River Authority (responsible for the flood protection and the EU Flood directive)
- Insurance companies
- Municipalities and farmers
- NGO's in the Záhorie region
Much lower attention has been given to the investigation and mitigation of flash and muddy flood phenomenon in Slovakia in comparison to other countries in northwestern Europe. There is also a lack of legislation concerning these natural hazards, nor are they adequately covered and taken into account in the insurance framework. Methods of land management, including land reclamation and change of agricultural practice,s need therefore to be popularized and implemented. These factors provide potential and opportunities to the project to involve all stakeholders to propose, design and test nonstructural flood and soils protection measures both on the conceptual, regional and practical field level. These would rely both on catchment-scale measures suggested for the whole catchments and traditional flood protective measures such as built infrastructures.
Gender and stakeholder workshops
In Slovakia both stakeholder workshops had a gender-balanced group of 5 women participating and, respectively,7 and 8 men. A typical role for women was representing an NGO, whilst the men were farmers, the roles of mayor and a water authority were represented by both men and women. For the women, an increase in soil fertility was considered an important issue, whilst the men mentioned the increase of crop production as an important value of soil as an Ecosystem Service. In relation to different sustainable land management approaches, the women mentioned legislative approaches, whereas the men were more concerned with the technical, agronomic and management changes in a farming system.
Lansdcape Atlas of the Slovak Republic. (2002): Bratislava: Ministry of Environment of the Slovak Republic, 344 pp.
Stankoviansky, M. (1997): Anthropogenic Transformations of Landscape in the Myjava Kopanitse. Environment, 31, 84 – 89 (in Slovak, with English Abstract).