Dotter project: watercourse management gets better, more sustainable and more efficient
Published: 30 November 2016
Flows in streams and other watercourses such as locks and canals have to be kept unblocked so that rainwater is drained effectively and incoming water flows go to the right place, preventing flooding and safeguarding water supplies. However, large amounts of vegetation can interfere with water flows. In general, water authorities in the Netherlands outsource mowing work on their watercourses and draw up specifications on the basis of visual and local inspections. But removing all the vegetation is bad for the ecology, is counter to the spirit of the Flora and Fauna Act and it does not bring WFD objectives any nearer. In addition, a more targeted approach –that sometimes actually costs less – will achieve the same results, or even improve them, in terms of hydraulics and ecology.
Implementation of mowing strategies
The aim of the Dotter project, which began a year ago, is to help water managers with the implementation of mowing strategies. In that way, good incoming and outgoing flows are guaranteed without unnecessary ecological damage in and around the water. A full-spectrum camera mounted on a drone or boat is used to make complete images of watercourses. The camera uses the reflection of visible and invisible light to distinguish between vegetation and other elements such as open water and shoring.
The images are then automatically interpreted, in part to determine the type and quantity of vegetation. The resulting data are used to calculate the flow resistance caused by vegetation and to identify ecological values. In time, information about sludge on the bed will also be included. All these data are linked to computer models for incoming and outgoing water flows, making it possible to map out the watercourses in a large area in a relatively short space of time. In addition, the mowing work can be tailored, with interventions being confined to specific locations. This protects the ecology elsewhere in the watercourses and makes mowing more targeted and more efficient.
The first field trials with the camera in the Netherlands were conducted at testing locations managed by the Rivierenland and Aa & Maas water authorities in the Linge river and in the Lage Raam stream. The camera was tested in combination with an RPAS/drone last September in the River Experiment Centre (REC) at the South Korean Institute of Civil Engineering and building Technology (KICT). Specific scenarios can be tested at full scale and in controlled ways at this large-scale outdoor facility. Another partner on this TKI project is the University of Twente.
It should be possible to actually use the technology in practice and at a larger scale in about a year from now for the management of watercourses by the Dutch water authorities.