Tasks – Research Fields:

• Rain simulation: runoff and infiltration propertiesof Alpine soil-/vegetation complexes
• Runoff and erosion research – Development and measures for run-off prevention and erosion control
• Hydrology of Alpine catchment areas – development of model approaches
• Applied Soil physics – Method development and routine analysis
• Soil mapping - alpine pedology
• Vegetation as run-off indicator? Run-off prediction
• Vegetation mapping
• Snow hydrology, winter floods
• Development of guidelines for hazard zoning considering vegetation, pedology, hydrology and snow hydrology aspects.
• Water budget, climatology and biometry in high mountain afforestations and alpine forests
• Development of silvicultural management concepts for High altitude afforestations
• Set up of a database and update of (snow)hydrologcial, soil, vegetation and erosion data.
• Runoff and erosion prediction based on statistical calculation and data interpretation data from the Irrigation database.
• Knowledge transfer for practical application - publications, papers, excursions, training sessions and advisory services as a support to the Provincial Torrent and Avalanche Control Service, the Austrian Ministry of Agriculture, Forestry, Environment and Water Management, universities, forest services and forest enterprises.

Cooperation partners:

• Forest Technical Service of the Torrent and Avalanche Control
• Institute for High Mountain Research, Alpine Agriculture and Forestry, University of Innsbruck
• Institute for Geography, University of Innsbruck
• Branch of Hydrography of the Office of the Provincial Government of Tyrol
• Inst. for Environmental Geology and Ecosystems Research, Joanneum Research, Graz
• Inst. for Water Management, Hydrology and Water Engineering, BOKU Vienna
• Provincial Forestry Direction of Tyrol
• Bavarian Office for Water Management, München
• Inst. for Applied Geology, BOKU Vienna
• GEOÖKO Dr. Herbert Pirkl, Vienna

Contact

Rain simulation: Run-off and infiltration properties of Alpine soil/vegetation complexes

In 1990, the Department of Avalanche and Torrent Research of the Austrian Federal Office and Research Centre for Forests has initiated run-off coefficient measurements through irrigation experiments using the model of a portable erosion and run-off measuring device according to KARL and TOLDRIAN (Bavarian Office for Water Management, 1973). By means of artificial heavy rain (MARKART und KOHL 1995) during which the evaporation from soil and vegetation equals cero that part of precipitation is recorded which runs off superficially (Ao). If necessary, also the interflow (subsurface flow) is quantified. Interflow is that part of the run-off that percolates somewhat delayed through the soil under the influence of gravity as groundwater after a rainfall. The size of the area may vary between 50 and 100m² and is generally 80m². Accompanying investigations include soil moisture monitoring using TDR, soil physics, soil maps and vegetation analyses . The measuring data collected through many years are entered into an irrigation database .

In 2001, a sprinkler was developed for the simulation of continued rain of low intensity. This allows to impinge larger slope segments (400m²) over a longer period (days).

The sprinkler is used also for other problem issues, e.g. quantification of the water budget of high altitude stands (interception performance,...) or the identification of soil/vegetation complexes under varying management.

Surface and erosion research - Development of methods and measures for run-off prediction and erosion control

In order to get some information on run-off and erosion disposition of different soil/vegetation units in torrential watersheds selected experimental plots have been irrigated by means of a portable sprinkler. The aim of the irrigation experiments is to simulate heavy rains and to measure the erosion caused in temporal relation to the duration of the irrigation. In addition, field and laboratory analyses of important soil physiological parameters are carried out in combination with vegetation research in order to get more information on the percolation and erosion potential of the soils.

Experimental erosion studies on representative sites are to allow for calibration of large-scale modelling of erosion and sedimentation rates.

Investigations in Meran 2000 (MARKART and KOHL 2000) and in the watershed of the river Großsölk (STMK; KOHL et al. 2002) document the different stages of erosion on different experimental plots, as follows:

covered with vegetation, not grazed < covered with vegetation, grazed << vegetationless

Hydrology of Alpine watersheds, model approaches - run-off coefficient maps

The results of selective measurements and observations (irrigations, soil physical characteristics, vegetation mapping ...) and data with aerial information (orthophotographs, soil maps, vegetation maps...) are combined with an irrigation database. The database includes meanwhile files on more than 700 irrigations including the results of the accompanying investigations from the Eastern Alps. Based on the mentioned information a run-off coefficient map is being elaborated.

Already in 1974, ZELLER published for the first time his hydrological model for the assessment of peak run-offs in torrential watersheds Due to the need of multiple iterations and the poor data pool concerning run-off coefficients and heavy rain, this model has not been used in Austria at all or only with extremely simplified model approaches. By means of an EXCEL - programme designed at the Department and supported by additional information on precipitation and run-off coefficients, it was possible to gain more experience with the model and its elements in the original proposed form and to adapt it to today's standards. (STEPANEK et al. 2002).

Applied soil physics/development of methods and routine analysis

The soil physical laboratory in Innsbruck offers the following analyses:

• Particle size distribution - texture
  The analysis is carried out in three phases, according to ÖNorm L 1061, following a modified approach:
  • sieving of air dried soil samples to a size of l2 mm
  • fractioned sieving between 2 mm and 40 µm
  • identification of the fine fraction <40 µm with particle size analyzer of the type SHIMADZU SA-CP2/10 (particle size determination according to the principle of optical refraction via combined sedimentation and centrifugal method).
• storage density (LD - according to ÖNorm L 1068)
• organic solid density (FD)
• determination in the gas pycnometer (Micromeritics, AccuPyc 1330).
• organic substance(OS)
  The OS is determined as loss by combustion of the weighted sample dried at 105°C by incineration in a muffle type furnace at 500°C .
• pF-curves
  

Soil mapping - Alpine pedology

For the elaboration of run-off coefficient maps the most important pedological characteristics of the studied watershed are identified by means of soil maps. Investigations by KOHL (1993) in the watershed of the Löhnersbach and the interpretation of the irrigation database suggest that the infiltration rate of alpine soils depends first of all on the vegetation, the type and intensity of management or land use and soil physical properties (macro pores, skeleton...). The soil type is of minor importance (with the exception of hydromorphic soils).

Vegetation mapping, vegetation as an indicator for run-off ? Run-off prediction

Change of spatial extension of different vegetation units (left :mapping dating back to 1953 according to SCHIECHTL, right : dating back to 1996 according to SCHIFFER and BURGSTALLER

The indicator function of the vegetation (indicator values) is used to draw conclusions on predispositions for the formation of run-off (KOHL 2000). Existing indicator values (moisture, dispersity, humus, life-form, sociologic behaviour,...) are combined to get a "run-off indicator value". GIS-based processing of vegetation maps allow to establish runoff-potential maps and to draw conclusions concerning development scenarios. By this method it is possible to establish links and synergies to ongoing research projects at the Department of Torrent and Avalanche Research at the BFW.

Another objective of the project is to study the influence of biomass on the run-off. For this purpose, precipitation experiments are used in order to allow conclusions on infiltration impediment and roughness of the vegetation. These conclusions will be important for precipitation-run-off modelling both quantitatively (run-off coefficient) and qualitativey (concentration time).

Water budget, climatology and biometry in high-altitude afforestations and alpine forest stands.

Studies by MARKART (2000) on the quantification of the water turnover of high-altitude afforestations in the area of Haggen in the Tyrolean Sellraintal provide the basis for the assessment of hydrological efficiency of future afforestation projects.

Each investigated plot shows a typical course of soil moisture under given meteorological conditions which is either due to the species growth - afforestation with Pinus cembra and larch, in the open area with Calluna vulgaris - or to the age and density of the afforested stand:

Very dense Pinus cembra afforestations with large needle surface (19 bis 23 m²/m²) may store in the crown 4 mm and up to 6 mm in the crown during extremely heavy rain.

Irrigation database: Runoff- and erosion prediction based on statistical calculations and data interpretation from the database.

The monograph by MENDEL (2000) reports that many studies on run-off formation have been carried out so far worldwide . However, there is a great demand by practitioners for concrete run-off coefficients within specific projects and objective criteria for the assessment of run-off coefficients in general. By merging the huge mass of information gained through heavy rain simulation in torrential watersheds into a unified database (MARKART et al. 2001), it was possible to develop new tools, e.g. a field instruction for the assessment of surface run-off during convective rainfall (MARKART et al. 2002).