ALPMON FINAL REPORT - ARC systems research

Contract ENV4-CT96-0359 ALPMON
can be improved significantly. The SPOT 4 sensor delivers images with 20m resolution in the multispectral
bands and 10m resolution in the panchromatic band. Furthermore, the middle infra-red
spectrum has been added, compared to the former SPOT sensors. The combination of the higher
resolution and the availability of a middle infra-red band proves to be a big advantage with respect to
the classification of alpine vegetation parameters. SPOT 4 data are available on request since 1999. It
is strongly recommended to use these data instead of Landsat TM images for a detailed investigation
of forest parameters as well as other Alpine vegetation with respect to the parameters required for
avalanche risk models.
Some constraints have to be mentioned concerning two non forest land cover categories. The
requirement of the customer to separate different types of grassland with respect to their use could not
be fulfilled with the available satellite data. The only separation could be made between rich and poor
grassland, which in most cases is related to the meadows in the valleys vs. the alpine pastures above
the forest border line. Furthermore, the rock size could not be classified with these data. This might
become possible with the high resolution sensors, having in mind texture features and the amount of
shadow within a pixel.
In general it can be stated, that areas outside the forest can be classified due to their spectral variation
if they occur on large areas. Smaller areas, which are covered by a mixture of vegetation categories,
such as rhododendron, dwarf mountain pine or smaller moor areas that do not exceed 1 ha, cannot be
classified definitely because of the mixed pixel problem. Simulations have proved that a geometric
resolution of about 5 to 10m in the infrared spectral range is necessary to assess the typical small-area
distribution pattern of vegetation outside of forests. The future sensor systems will provide data in this
resolution range.
Other decisive criteria related to the morphology (slope, aspect, curvature, and flow length) could be
derived from a digital elevation model. However, the currently available DEM resolution (25m) is too
rough to detect morphological surface characteristics, that might affect avalanche release, such as
shape of slope (convex/concave) and length of slope in non forested areas or areas with critical forest
canopy density, in sufficient detail. Here, high resolution laser scanner models could deliver valuable
information. But due to the high costs for these data the information should be restricted to the areas
that have been defined as (very) critical in the first steps an hierarchical risk assessment, including the
aspect of vulnerability.
The time resolution is another crucial factor for information extraction. A yearly update in general
seems to be possible with the currently available satellite systems. The bottleneck might be the
availability of images from winter with the specific snow situation required. On the other hand, the
distribution of dwarf mountain pine and greenalder shows no extensive variations. Therefore, an
update of this information within a 5 years period seems to be sufficient and practicable.
Finally, it should be taken into consideration that satellite image classification in general could also be
used as a tool for updating the information on infrastructure that is exposed to avalanche damage,
implemented in a GIS.
2.3.4 Erosion Risk Assessment, Cordevole Test Site (RSDE)
2.3.4.1 Introduction and Objectives
The assessment of erosion risk is a primary problem in mountainous regions. The purpose of this
feasibility study was to develop a proper methodology for the production of erosion risk maps in these
regions exploiting information derived from remote sensing technology.
The review of the existing studies on soil erosion indicates that current basic methodologies have been
established primarily to assess soil erosion risk over agricultural and hilly areas in temperate climate.
These methodologies therefore cannot be directly applied to a much more complex system, such as
the alpine environment. Further, the use of a single methodology could hardly account for all the
features of the alpine erosion phenomena. In fact, besides common erosion processes, other relevant
processes increase the transformation rate of the alpine landscape. The most widespread erosion
models like USLE/RUSLE or CORINE EROSION cannot be successfully applied to the alpine areas
because they have been conceived to work on hilly terrain for agricultural purposes where sheet and rill
erosion processes are prevailing. Mass erosion processes typical of alpine environment like debris
flows are not taken into account in these models. Further, CORINE EROSION is not considered a
suitable model for regional planning applications at scale 1:25.000 as required by the customer.
JR, RSDE, ALU, LMU, Seibersdorf, WSL 43