Quantification of landscape evolution on multiple time-scales

Essential information about the activity or even the mechanics of
tectonic and erosional processes can be extracted from their
surface expression. For this purpose, it is necessary to
appropriately constrain the temporal as well as the spatial
framework, in which to consider a specific process. While recently
developed dating techniques, such as thermochronology or
radiocarbon dating, allow to assess the age of landforms and
therefore rates of tectonic and erosional processes, detailed
spatial information is also required to assess these rates
correctly. Due to a lack of appropriate topographic data in the
past it was sometimes challenging to reliably approximate the
spatial framework, because the size of a particular landform can
often cover a wide range of spatial scales. Recently available,
conventional topographic data, such as those of the Shuttle Radar
Topography Mission, substantially improved the definition of an
appropriate spatial framework due to their spatial coverage and
resolution of down to less than 1 m. However, to constrain this
framework at a detail beyond the resolution of several decimeter
terrestrial laser scanning provides a highly efficient approach.
This technique permits the rapid acquisition (within minutes) of
tremendous amounts of topographic data with both, a high resolution
of a few centimeters and a high accuracy of a few millimeters.
High-resolution topographic maps of a certain area of the surface
of the Earth are derived from individual laser-scanner
measurements, that in turn allow to characterize the in-situ
geomorphic setting at great detail. Moreover, repeated measurements
of this area allow to quantify morphological changes thereby
supporting the survey of surface processes on short-term scales
ranging from days up to several years. The former approach is best
suited for tectono- and the latter one for fluvial-geomorphic
studies, and we present results from two case studies that are
either based on single or repeated laser-scanner measurements. In
the first case, we combined field mapping and high-resolution
digital elevation model (DEM) analysis to evaluate the detailed
meter- to hundred meter-scale structure and surface expression of
one flank of the Rex Hills pressure ridge in the western United
States. Based on terrestrial laser scanning (Riegl LMS-Z420i) we
derived a DEM with cm-scale resolution and extracted
high-resolution topographic cross-sections. This enabled us to
identify fault scarps and determine their relative ages and
geometry. In the second case, we carried out a detailed field
mapping of erosion and sedimentation patterns in the Alp Valley,
central Switzerland, to assess its Holocene evolution.
Simultaneously, we conducted repeated high-resolution (less than 1
cm locally) laser-scanning surveys (Topcon TLS-1000) along two
tributaries, the Erlenbach and Vogelbach, to determine
channel-morphology changes and the nature of shortest-term sediment
transport by comparing the individual DEMs derived from these
measurements, as well as to evaluate the context to the longer-term
evolution of the Alp Valley. Both case studies, however, highlight
the potential of medium-range laser scanners with measurement
distances of up to hundreds of meters. Such scanners are most
appropriate to efficiently analyze closely-spaced fault scarps
across a broad range of spatial scales, and to document complex
morphologic changes in small mountainous torrents due to sediment
transport. Moreover, terrestrial laser scanning is a key tool to
monitor surface processes, but the insights gained from this method
are generally evaluated best in the context of further data sets
including geochronological, structural, subsurface, or climate
data. Surface processes, in particular erosion, sediment transport,
and deposition in sedimentary basins are intermittent in space and
time challenging both, the appropriate definition of a
spatiotemporal framework addressed above and a comprehensive
process understanding. A major objective of this thesis is to
contribute to a better understanding of scale linkage concerning
these processes. We therefore first carried out a comprehensive
comparison of short- to long-term erosion measurements from the
Alps based on an approach originally established to evaluate the
significance of geologic and geodetic measurements along
intra-continental faults on time scales of millions to tens of
years. In a second step, we re-assessed the sediment budget of the
Alps, a data set that is usually considered to be an appropriate
measure of long-term erosion in the Alps. The two major results of
both studies indicate that: short- and medium-term erosion in the
Alps over years to ten thousands of years is dominantly influenced
by climate and weather variability, e.g., due to seasonal
differences in the amount of precipitation; whereas long-term
erosion over millions of years is controlled by tectonic processes.