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While
long term erosion rates may be estimated by dating methods, current day
erosion rates are – if at all available – based on rough estimates
or on point measurements. Precise quantification of short term erosion
rates are required to improve our understanding of short term processes,
for input in landscape evolution models, as well as for studying the
mechanics and efficiency of different erosion processes in varying
geomorphological settings. Typical current day erosion rates in the
European Alps range from sub-millimetre to several millimetres per year
depending on the dominant erosion processes. IP2 will utilize a new
innovative surveying technology for quantification of in-situ bedrock incision in fluvial channels of the
Swiss Alps.
The
level of surveying accuracy required for recurring sub-millimetre to
millimetre measurements of the same area in the field is demanding.
Point probing techniques require a rock anchor as reference point
disturbing the vicinity of the sampling area and such measurements are
only valid for a very limited part of a bedrock channel. A precise
method for quantification of areas larger than 1 m2 with
sub-millimetre accuracy is “badly needed”, but not available off the
shelf. The method should be non-contacting as well as non-disturbing and
suitable for field use even in remote areas. Latest developments with
image assisted measurement techniques will be utilized to provide such a
method. It combines the pointing precision of a theodolite with the
ability of mass point measurement from stereo imagery.
The
input of IP2 to SedyMont is:
- Optimization of an image
assisted total station system for measuring in-situ bedrock incision
with sub-millimetre accuracy.
- Quantification
of in-situ bedrock incision in fluvial channels of the Swiss Alps. Test sites are Erlenbach, Rotenbach and Illgraben (all in
Switzerland).
The
objectives require development and implementation of an
image assisted total stations (IATS) for measurement of bedrock erosion.
Main test site will be the derbis flow channel of the Illgraben. An
annual average of 3-5 debris flows have been observed in the Illgraben. Bedrock erosion in the channel is at the order of 1 mm per event
(personal observation). Frequency and magnitude of debris flow events in
the Illgraben should provide sufficient basis for evaluation of the IATS
method as well as for accurate quantification of in-situ bedrock erosion
over the duration of the project. Additional data will be collected in
the Flysch bedrock of Erlenbach and Rotenbach catchments. Estimated
erosion rates in the fluvial channels are less than in the debris flow
channel of the Illgraben, but should exceed 1 mm per year.
The main goal of IP2 is
to develop, implement and provide an image-based measurement system for
the task for quantification of bedrock erosion in fluvial channels. The derived data will support the analysis of IP1. |
