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| Titel |
Assessment of gully erosion by linking photogrammetric methods and field measurements |
| VerfasserIn |
Florian Kluibenschädl, Stefan Strohmeier, Andreas Klik |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076821
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| Zusammenfassung |
| In the Ethiopian Highlands, numerous processes lead to land degradation thus decreasing soil
productivity. The objective of this study is to assess the gully erosion in an agriculturally used
watershed in the northern Amhara region of Ethiopia. The study uses two different methods
to measure the development of four active gully reaches within one system: 1) manual
recording of various cross sections using tape measurements and 2) application of
close range photogrammetry. Fieldwork was conducted from June to September
2012.
Overlapping photographs, taken with a non-metric digital camera, were taken as input data
for a detailed photogrammetric analysis. The goal was to assess the applicability of this rather
new remote sensing method in the given domain. In addition, the total soil loss due to gully
erosion was evaluated for different reaches of the gully system in a catchment of 34
ha.
In order to provide comparison and backup data, as well as for verification purposes, the field
work was designed to incorporate manual plumb line and tape cross section measurements.
Both methods where applied at the beginning, the middle and at the end of the rainy season.
The work uses geo-referenced buried stones to retrace the location of 22 cross sections at four
gully reaches. These marks were also necessary to add a consistent outer orientation to the
dense surface point clouds resulting from photogrammetric analysis. The control
points are then excluded from the photogrammetric reconstruction process and used
for error estimation. The software package Photomodeller Scanner®Â allows for
the derivation of surface models from point clouds. Comparing the surfaces from
different points in time for a specific gully reach reveals the volumetric soil loss in this
area.
The manual measurements of 22 cross sections show an increase in area of up to 136%. At
the top most active gully reaches this relates to a soil loss of greater than 17 m3 within a 21 m
long gully segment. The interpretation of the stereo photos is still in progress –
no data is yet available. One interesting aspect of this data deals with vegetation.
There was almost no vegetation cover affecting the photogrammetric survey at the
beginning of the rainy season, however this changed over the course of the survey. A
comparison of manually measured cross sections with digitally derived ones, will give
some indication of the influence of vegetation on the photogrammetric approach. |
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