The effects of human activity on geologic, biologic and atmospheric processes are now larger than at any point in Earth’s history. As a consequence, scientists constituted a new geological epoch, called "The Anthropocene". In the present article, Ronald Pöppl, Geographer at the University of Vienna, talks about his research on the geomorphic consequences of river engineering and land cover changes showing examples from Lower Austria. Some of his latest results on the geomorphic legacy of dams he will also present at a press conference entitled "The Anthropocene: are we living in the age of humans?" at the "European Geosciences Union" (EGU) General Assembly 2014 in Vienna.
Anthropogeomorphology, which is the study of the human role in creating landforms and modifying geomorphic processes, is a relatively young discipline and one of the research foci of the working group ENGAGE-Geomorphological Systems and Risk Research at the Department of Geography and Regional Research at the University of Vienna. "Humans continuously alter the shape of the Earth’s surface - either directly such as by construction or excavation works - or indirectly such as due to land cover conversions that further modify the rates of erosion, transport and deposition of sediment", says Ronald Pöppl, Senior Lecturer at the Department of Geography at the University of Vienna and member of the working group ENGAGE. How humans change the "Face of the Earth - Process and Form" is the main theme of the "European Geosciences Union" (EGU) General Assembly 2014 - the largest conference for geoscientists in Europe.
On the geomorphic legacy of dams - case study Kaja River, Lower Austria
By constructing dams, humans alter the sediment dynamics of river systems which induces geomorphic processes that modify the morphology of river channels and therefore the shape of the Earth’s surface. Besides the accumulation of sediment in the reservoirs and upstream river reaches, channel bed and bank erosion occurs downstream of dams as a consequence of dam-induced sediment depletion.
These dam-induced changes in sediment dynamics and channel morphology involve a range of negative consequences for humans (e.g. infrastructure affected by erosion) as well as for flora and fauna (e.g. alteration of riverine habitats) that often require the removal of these structures. However, dam removal again induces geomorphic channel changes such as erosion in the river reaches upstream of the former dams as the river seeks for a balanced channel slope.
To counteract the geomorphic consequences of dam removal channel bed and bank protection measures are often being installed. These measures however prevent geomorphic channel recovery, thereby preserving a dam-induced and therefore man-made relief. This situation can also be observed along the Kaja River, a tributary of the Thaya River in the north of Lower Austria.
The influence of riparian vegetation on river channel morphology and lateral sediment input - case studies Lassing River and Fugnitz River, Lower Austria
The type of riparian vegetation has a substantial influence on channel morphology as well as on the rates of lateral sediment input to river systems. On the one hand, roots of riparian trees stabilize the river banks which reduces bank erosion (e.g. observed along the Lassing River, southern Lower Austria). On the other hand, these roots facilitate the establishment of natural levees that further reduce the lateral input of fine sediment and associated pollutants from adjacent agricultural fields. This phenomenon has been observed by Pöppl et al. along the Fugnitz River, a tributary of the Thaya River in the north of Lower Austria.