Integrated assessment of geomorphologic process dynamics in the Ethiopian Highlands using remote sensing and advanced modelling approaches
Final Report Abstract
Working on the acquisition of area covering data on mass wasting processes in the Ethiopian Highlands, the following results and major project outcomes could be summarized: The multi-temporal remote sensing data evaluation for landslide mapping, consisting of the complementary-use of historic aerial photography (reconstruction of landslide evolution in time) and new space borne very high spatial resolution remote sensing sensors (geometrical control) enabled a clear identification of the secondary triggering effects on the reactivation of landslide accumulations due to anthropogenic activities, comparing three large slope failures close to Dessie. Fast urban sprawl leads to the construction of houses and infrastructure on the outskirts of the city (including the landslide hazard areas) over the last 8 years. Post-slide movements of larger landslide accumulations like in Debre Sina were analyzed quantitatively using optical feature tracking methods (horizontal movements) and space borne LIDAR systems (vertical movements), providing new information on the landslides extent, kinematics, zonation and evolution over time. The generated OEMs and their derivatives (morphometric terrain indices) provided useful information on the detailed morphology and the related processes, meanwhile the ICESat surface elevation measurements seems to be the first time ever that a space borne LIDAR sensor was used for the validation of a landslide accumulation body. For the area wide stochastic analysis of these processes, two methods, the Boosted Regression Tree (BRT) and the Maximum Entropy Method (MEM) were applied in order to extrapolate from visual inspected high resolution remote sensing data the two classes "landslide" and "debris flow" (training data set) onto widespread areas along the Ethiopian Highlands. Valley depth, channel network base level as well as slope are the most important variables. The landslide and debris flow susceptibilities are related to stratigraphic units and the drainage system. The approach has been applied both to the Jemma Basin and to the upper Awash River system. Gully erosion is a widespread problem over semi-arid Northern Ethiopia, we have shown, that quantitative measurements and areal mapping are possible with the evaluation of air borne and space borne archive data (Kropacek et al. 2016). The innovation is the areal process related mapping - badlands, rill erosion, gully erosion were mapped individually, enabling the estimation of eroded sediment as source of suspended load within the river systems. A complex stochastic modelling approach has been developed for the Andit Tid basin, which is located in the upper Jemma catchment. The analysis take into account: i) sheet erosion, ii) gully erosion and iii) badlands. The Maximum Entropy model was applied on the process and forms inventory to explore their relationships with a set of spatial attributes obtained by the ALOS PRISM DEM, Rapid Eye and multispectral ASTER images. Thus, finally one single susceptibility map was generated for the three processes under investigation namely Badlands, sheet and gully erosion features and related processes. Detailed geomorphological mapping was carried out using an integrative methodology comprising visual inspection of aerial photography, semi-automated classification of high-resolution satellite imagery as well as sophisticated geomorphological process mapping in the field. Sheet and gully erosion processes are triggered by anthropogenic agriculture and overgrazing due to cattle farming causing soil compaction and a resulting increased surface runoff. The map contributes to the understanding of the landscape evolution and provides information about possible erosion related hazards.
Publications
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2015: Reactivation of mass movements in Dessie graben, the example of an active landslide area in the Ethiopian Highlands. - Landslides, 12(5): 985 - 996
Vařilová, Z., Kropáček, J., Zvelebil, J., Štastný, M. & Vilímek, V.
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2015: Remote Sensing for Characterisation and Kinematic Analysis of Large Slope Failures: Debre Sina Landslide, Main Ethiopian Rift Escarpment. - Remote Sensing, 16183 -16203
Kropáček, J., Vařilová, Z., Baroh, I., Bhattacharya, A., Eberle, J., & Hochschild, V.
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2015: Terrain analysis and landforms recognition. - In: Clarke, LE. & Nield, J.M. (Eds.): Geomorphological Techniques (Online Edition). British Society for Geomorphology, London
Schillaci, C, Braun, A. & Kropáček, J.
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2016: Analysis of the influence of tectonics on the evolution valley network based on the SRTM DEM, Jemma River basin, Ethiopia. - Geografia Fisica e Dinamica Quaternaria, 39: 37 - 50
Kusák, M., Kropáček, J., Schillaci, C. & Vilímek, V.
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2016: Assessment of gully erosion in Upper Awash, Central Ethiopian Highlands based on comparison of archived aerial photographs and very high resolution satellite images. - Geografie Fisica e Dinamica Quaternaria, 39:161 - 170
Kropáček, J., Schillaci, C., Salvini, R., Märker, M.
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2016: Combined method for risk assessment of mass movement and erosion susceptibility in the Ethiopian Highlands. - AUC Geographica, 51 (1): 17 - 28
Nechyba, M., Vařilová, Z., Kotva, P., Kropáček, J., & Zvelebil, J.
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2016: Stochastic assessment of landslides and debris flows in the Jemma basin. Blue Nile, Central Ethiopia. - Geografia Fisica e Dinamica Quaternaria, 39 (1): 51 - 58
Märker, M., Hochschild, V., Maca, V., Vilímek, V.
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2017: analysis of Significance of environmental factors in Landslide Susceptibility Modeling: Case Study Jemma Drainage network, Ethiopia. - AUC Geographica, 52 (1): 119 - 126
Maca, V. & Smolikova, J.
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2018: Morphometric terrain analysis to explore present day geohazards and paleolandscape forms and features in the surroundings of the Melka Kunture prehistoric site. Upper Awash Valley, Central Ethiopia. - Acta Universitatis Carolinae. Geographica. Univerzita Karlova: 10-19
Märker, M., Schillaci, C. & Kropáček, J.
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2019: Geomorphological processes, forms and features in the surroundings of the Melka Kunture Palaeolithic site, Ethiopia. - Journal of Maps 15 (2): 797-806
Märker, M., Schillaci, C., Melis, R.T., Kropáček, J., Bosino, A., Vilímek, V., Hochschild, V., Sommer, C., Altamura, F. & Mussi, M.
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2019: Historical aerial photographs for investigation of landscape dynamics and mass movements on the Ethiopian Highlands. - Land Degradation and Development, 30 (5): 483-493
Kropáček, J., Vařilová, Z., & Nyssen, J.
