Schlüsselwörter
(Englisch)
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Mountains; erosion rates; land use type; Cesium-137; erosion modelling; Universal Soil Loss Equation; Alps; Switzerland; grassland degradation
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Forschungsprogramme
(Englisch)
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COST-Action 634 - On-and Off-site Environmental Impacts of Runoff and Erosion
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Kurzbeschreibung
(Englisch)
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The Alps represent one of the most sensitive ecosystems in Europe because of aggressive development in the recent past, large numbers of tourists and severe environmental damage enhanced by acid deposition and global warming. Degradation of soils due to soil erosion and landsliding seriously threatens the mountain environment and is of major concern to European governmental offices. Mapping and quantification of soil erosion has been studied in numerous projects for agricultural soils in lowlands or low mountain ranges. However, so far very few studies and scarce information exist on soil erosion and soil degradation in mountain or alpine environments. This project will address soil degradation in an alpine environment with mapping and modelling of soil erosion. Existing erosion models will have to be redefined to meet the alpine characteristics. The GIS-based soil erosion modelling will be validated by new mapping techniques in the field which consider the specificity of alpine systems. Mapping will be supported by quantification of erosion rates with sediment traps. The research will focus on the upper Reuss watershed (Furkareuss) where the degradation of soils has been shown to be dramatically impacting the valley slopes.
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Weitere Hinweise und Angaben
(Englisch)
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Full name of research-institution/enterprise: Universität Basel Department of Geosciences Institute of Environmental Geosciences
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Partner und Internationale Organisationen
(Englisch)
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AT, BE, CH, CZ, DE, DK, ES, FI, FR, GR, HU, IE, IT, LT, LU, LV, NL, NO, PL, PT, RO, RS, SK, UK
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Abstract
(Englisch)
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The project 'Quantification of soil erosion in an alpine watershed of Switzerland (Kanton Uri)' consists of three parts. The first part includes the transfer of different soil erosion measurements (sediment traps, sediment cups and Cs-137) to alpine hill slopes. The empirical soil erosion model Universal Soil Loss Equation (USLE) has been applied in a second part of this work. The USLE is one of the most widely used models because its low data requirement to estimate soil erosion rates under different conditions (management practice, slope length and steepness, precipitation amount, soil property, terracing). The third part contains the application of the frequently used soil erosion model WEPP (Water Erosion Prediction Project) to prove the validity of this physical erosion model in steep alpine grasslands. Three land use types were investigated within this work: hayfields, pasture with dwarf shrubs and pasture without dwarf shrubs. These different land use types are dominant in the valley. Mean annual soil erosion rates based on Cs-137 measurements ranged between 4.7 t ha-1 a-1 for pastures with dwarf shrubs to >20 t ha-1 a-1 at hayfields and pastures without dwarf shrubs and are thus 10 to 20 times higher compared to previous measurements in alpine regions. Our measurements with Cs-137 integrate over the last 22 years, whereas previous studies mostly reported erosion rates based on summer time, short term irrigation experiments. Furthermore, results indicated that land use has an influence on soil erosion rates. Cs-137 based erosion rates were compared with erosion rates which we determined with the Universal Soil Loss Equation (USLE). The comparison was done to verify the validity of USLE in a steep alpine region. Results of the USLE are in the same order of magnitude as Cs-137 based erosion rates even though slopes are quite steep. However, the uncertainty of the results is not known since the slope steepness is not within the valid range of the USLE and therefore not empirically ensured. ln addition to the USLE we tested the WEPP model (Water Erosion Prediction Project) to describe the soil erosion in the Urseren Valley as it seems to be one of the most promising models for steep mountainous environments. Crucial model parameters were determined in the field (slope, plant species, fractional vegetation cover, initial saturation level), by laboratory analyses (grain size, organic matter) or taken from the WEPP manual (soil erodibility, effective hydraulic conductivity, cation exchange capacity). Erosion rates were measured with sediment traps during the vegetation period between June 2006 and November 2007. Long-term soil erosion rates were estimated by measuring Cs-137 redistribution, deposited after the Chernobyl accident. ln addition to the erosion rates, soil moisture and surface flow was measured during the vegetation period in the field and compared to model outputs. Short-term erosion rate simulations for the vegetation period in 2007 are in agreement with measured erosion rates. However, simulated soil moisture is up to two times higher than measured field data. Furthermore, simulated soil moisture has an opposite dynamic compared to measured field data (increasing in springtime) and surface flow is not simulated correctly. Snow cover melting is simulated too late compared to field observations and thus water from snowmelt is available until summer time. We assume that these differences lead to the general overestimation of erosion rates for long-term rate erosion predictions for ail three land use types. Thus, the WEPP model could be a useful tool for alpine regions during the vegetation period to assess the influence of different land use conditions but should be applied carefully during winter time and on snow covered regions. Our study demonstrates the need of soil conservation strategies for alpine regions since erosion rates are much higher than previously reported. Furthermore, results of the WEPP model are only partiy comparable with measured data on respective slopes. Long-term erosion rates of the USLE are comparable with measured data but not valid for steep slopes. Hence, existing models have to be adapted to alpine regions or new soil erosion models have to be designed for steep mountainous slopes.
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Datenbankreferenzen
(Englisch)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C05.0074
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