The so-called "Naufahrten" are waterside monitoring and inspection tours, which are conducted periodically (10 times per year in the free flowing sections east of Vienna and in Wachau, 4 times in the backwater sections) and provide essentail basic data for several corporate divisions.
As the Naufahrten are an integral part of viadonau´s waterway management, special attention is paid to the monitoring of the fairway channel by means of basic single-beam soundings. The overall fairway condition, especially in ford areas but also in widened areas (e.g. port entrances) and lock areas, is assessed in this way. This activity provides first pieces of information about possibly necessary subsequent measures. Additionally, the completeness, the location and the condition of water- and landside navigation signs (notice marks, rhythmic lights and buoys) is monitored.
The Naufahrten also entail a waterside, systematic visual check of the general state of the riverbanks and hydraulic structures (groynes, flood protection dams, etc.) and are thus an important part of the water surveillance and provide information for the landside maintenance services. This proceeding permits the inspection of objects that are impossible or difficult to monitor from ashore.
The collected data is analysed and used to determine necessary maintenance measures on the Danube, its riverbanks or its hydraulic structures.
As part of the modernisation of equipment, the three previously used sister ships "Aschach", "Krems" and "Bad Deutsch-Altenburg" (year of construction 1998) were replaced by the two new and identically constructed vessels "Halbe Meile" (2016) and "Carnuntum" (2017). Since Juli 2016 the "Halbe Meile" is operated in the Danube section between the German-Austrian border and the power plant Melk (western section), whereas the "Carnuntum" is operated in the stretch between the power plant Melk and the Austrian-Slovak border (eastern section). The eastern section includes the two free flowing Danube sections in the Wachau and East of Vienna.
In 2018 both vessels were equipped with an anchor winch. This allows for the pulling of the buoys toward the vessels hull for the purpose of cleaning of the buoys or the maintenance of the remote surveillance units mounted on the buoys. Nevertheless, this does not replace the marking craft "Bojenleger 1", currently in operation. The comparably small Naufahrt vessels are not suited to place or lift buoys.
In the course of the revision of the Naufahrtsrichtlinie in 2022, it has been optimised in terms of energy and cost-saving potential. The number of trips was reduced by more efficient planning.