Fieldwork on Old Drava is in process

12-03-2018

The boat that implements the dredging was released on Old Drava in the beginning of March and the fieldwork could start within the frame of Old Drava LIFE project. The material of the river-bed has been extracted from a 500 metre long area.

First, an approximately 7000 m3 of mud had to be eliminated by dredging, after which the major part of the work, the construction of the sluice for water retention could begin. This oxbow of approximately 15 km was cut off from the river during the regulation of Old Drava, the river-bed of which has continually been filling up with mud since that time. By now an oxbow has been formed from the river-bed with various and diverse habitats and a riverside gallery forest. The Old-Drava LIFE project’s goal is to increase the water level and reduce the outflow of the water. It is favourable to the aquatic environment and the floodplain forest as well.

By the recent dredging we would like to enhance the conservation of the deeper and open water stage. The mud is eliminated with a thickness of 0,5-1 m in the area concerned by the intervention, so the water coverage will be that much deeper in these places. Thanks to this, rooted aquatic plants typical to the most part of the oxbow will cover the water surface to a less extent, so it will remain open for a longer time. Moreover, the deeper water will also be suitable for the overwintering of certain fish species.

We chose a hydraulically driven dredger as it disturbs the aquatic life of the oxbow on a minimum level. A floating excavator is launched into the water, which pumps up a mixture of mud and water and then returns it to the Drava through a pipe located in advance. Hence, there is no need to place mud on land. The implementation is expected to be terminated by the end of March.