Proglacial geomorphodynamics on catchment scale with airborne/terrestrial laserscanning

The project is part of a bundle studying geomorphic processes in rapidly changing proglacial systems in the alps at high resolution. The project serves the integration and evaluation of analyses of geomorphic processes in the investigated area conducted by other projects of the bundle. The aim is the collection and upscaling of measurements and process models from the plot to the catchment scale, in order to derive an improved understanding of the system. Primarily, the relations between processes shall be mapped very precisely. In a second step in the course of the bundle project, we also aim at predicting the future development under different environmental conditions, which is a very important issue especially in proglacial areas. An essential precondition for working on the catchment scale is the generation of a highly precise three dimensional topographic database. This is conducted by data acquisition with terrestrial and airborne laser scanning (TLS and ALS). In the proposed project, the monitoring of surface changes induced by material transport or deformation through TLS shall be increased in accuracy by a factor of two to five in comparison to current methodology for general setups. A similar challenge is found in ALS where accuracy across epochs in the range of two to five centimeters is targeted. It will be investigated if this can be achieved with epoch spanning strip adjustment. So far this has not been tried or proved yet. Geomorphological expert knowledge is incorporated in this process, including the preparation (definition of the stability of different areas) as well as the interpretation. Additionally, data capturing by full-waveform systems will be performed, which operates by digitizing the shape of the backscattered laser echo. This shall ensure that the consideration of the interaction of the laser pulse with the rough terrain surface in geometric and radiometic respect is possible. This analysis will provide more insight into the composition of the surface within the laser footprint. Another challenge in this project is the integration of ALS and TLS data, in orientation as well as in analysis; this results, amongst others, from the different viewing directions. The high resolution scanning data provides the basis for the process geomorphological relief analysis and the regionalization of sediment transport and yield built ontop for upscaling to the catchment level.

Aim of PROSA, (high-resolution measurements of morphodynamics in rapidly developing proglacial systems of the alps) is the investigation of the impact of the fast progressing glacial melting on the forms of the Earths surface. The temporal development by erosion, transport and deposition of material is in the focus of the research project. Debris flow, rock fall and flooding are some of the possible consequences expected to increase because of ongoing climate changes. Within PROSA the relation among different geomorphological processes and their changes will be quantified as a sediment transport budget. This required the collaboration of different disciplines, including geomorphology, geology, geophysics and photogrammetry. The acquisition and processing of high-resolution spatial data in a temporal stable coordinate system was the main contribution by the research group Photogrammetry -Vienna University of Technology, funded by the FWF) to this project. This is a difficult task, especially because stable areas are rare due to the permanent changing of the surface (e.g. melting of snow and permafrost, debris flow). Laser scanner were used for the measurements primarily. As a rather new technology, laser scanning is one of the main fields of research in photogrammetry at the Vienna University of Technology. Laser scanning can provide dense and precise measurements of the terrain, either from the earth (terrestrial) or from above (aerial). Aerial laser scanning was used within this project for the measurements of the whole study area twice. Changes of the Earths surface can be recognized by comparing these two data sets. Due to several error sources, the originally measured terrain points contain significant errors (up to several dm). An optimization method developed within this project reduces these errors to 1-2 cm. On the basis of this improved data, a detailed description of the present geomorphological processes was done by the involved disciplines in this project. For terrestrial laser scanning a new type of target was developed within the PROSA project. On one hand, the usage of these targets enable the automatic relative positioning of point clouds measured from different view points. On the other hand, the whole data can be transferred into a global coordinate system by using satellite-measurements. Multiple terrestrial laser scanning measurements were conducted within this project in order to observe terrain changes on specific slopes and to quantify material transports. The findings of the PROSA project lead to a deeper understanding of the ongoing processes in the Alps and consequently to a better assessment of natural hazards. In the end this increases the human protection from natural hazards. PROSA is a collaborative geoscientific project which is funded by the DFG (German Research Foundation / BE1118/27-2) and the FWF (Austrian Science Fund / I893-N24). The project was extended until 2016. 1