DEM-derived markers of drainage network changes in the Eastern Alpine Foothills
The study area is situated between the uplifting Alps and the subsiding Little Hungarian Plain, between 16°–17° E and 47°–47.5° N. The differential vertical motion implies neotectonic activity and some associated geomorphologic features (e.g. wind gaps, small streams in large valleys, etc.) may be observed as a result of drainage reorganization. After ∼8.7 Ma the area was characterized by a wide alluvial plain and a marsh zone. Later on, rivers spread their gravelly sediment over the whole area, creating gravel terraces in the west and an almost continuous gravel cover in the eastern, planar terrain. The drainage network in the hilly region is oriented to the NW–SE alluviation direction, but each river has several abrupt turns in its lower course.
In order to identify wide and planar features some DEM-derived markers were used. First, two parameters were considered for each pixel: slope angle and relative height. Second, two parameters were used to classify wind gaps: incision of the valley bottom and relative elevation. In our case, the less uplifted, but more deeply incised valleys are the most obvious markers of drainage reorganization. Using the mentioned methods, terraced valleys, wide alluvial valleys and deeply incised valleys, as well as wind gaps, are recognizable and help interpretation of former river connections.
The spatial pattern of the identified wind gaps suggests that drainage reorganization was significantly influenced by north-facing escarpments. Therefore, the map provides additional information to the scientific debate concerning the post-Miocene tectonic activity of the Eastern Alpine Foreland.