Channel Incision Along the Lower Drava

The Drava channel has not yet reached a hydromorphological equilibrium since the major human interventions two centuries ago. According to present knowledge, the fundamental reasons for prolonged channel entrenchment can be summarized in the following: 1. Among river regulation activities, the cutoff of bends should be emphasized. River length was reduced by about 40% and, as a consequence, current velocity increased. In addition, regulation structures narrowed down the channel and further accelerated flow. 2. Hydroelectric plants were built along the Upper and Middle Drava. In the reservoirs, the arriving masses of bedload and suspended load settle and this causes a sediment deficit on the lower section. 3. Channel dredging along the Hungarian Drava section (between Őrtilos and Dravaszabolcs) have also contributed to deepening of the channel. The rate of incision is not uniform all along the length of the river: upstream Barcs it is 4–6 cm y−1, while downstream, at the Dravaszabolcs gauge it is only 1–2 cm y−1. The average rate for the entire Hungarian section is 3 cm y−1.