Long-term shipping survey on the Wesel-Datteln canal (WDK)
In 2007, the traffic on the Wesel-Datteln canal (WDK) was observed over a period of two weeks in a shipping survey. The objective was to register the passage of all ships on the canal and to determine the corresponding authoritative parameters for hydraulic loading on the bed and banks. The resulting measurements are being used among others to validate and optimize existing calculation methods used in the GBBSoft rip-rap design software. The shipping survey included a digital radar system for registering the ships’ speeds and the ships’ distance to the bank, pressure sensors for recording ship-induced deflections in the water level and speed sensors on bank and bed for measuring flow velocities.
One result of the field test was that the speed limit for empty and loaded inland cargo ships of 12 km/h respectively 10 km/h was exceeded already in the mean value for empty vessels and reached for loaded ships. During this shipping survey, altogether half of the registered ships travelled at more than the corresponding speed limit (Picture 1). This reinforces the recommendation given in the GBB (Principles for the Design of Bank and Bottom Protection for Inland Waterways) to rate the rip-rap on inland waterways at 97% of the critical shipping speed.
Another aspect of the shipping survey consisted in comparing the measured wave heights and return current velocities with the values calculated in GBBSoft. Picture 2 shows an example of a wave event recorded with a pressure sensor caused by a passing large inland cargo vessel. The primary and secondary wave system can be seen together with the characteristic bow and stern wave heights. A comparison of the measured data with the calculated values confirmed for example the GBB design concept for stern wave height, which entails the depiction of a worst case. As shown in Picture 3, the calculated stern wave heights on the y-axis are in principle larger than the measured values and are, therefore, on the safe side when used for rating.
The measurements obtained with this shipping survey have been entered in a database together with various other field and model test data to keep them available for further use and reference in many comparison calculations.
BAW 2005: Principles for the Design of Bank and Bottom Protection for Inland Waterways, Mitteilungsblatt Nr. 88, Karlsruhe 2005.