The Delta Flume at De Voorst, located near Marknesse in the province of Flevoland, was a large experimental wave flume built for hydraulic engineering research. It belonged to the outdoor research site of the Waterloopkundig Laboratorium (later known internationally as Delft Hydraulics Laboratory).

The flume was constructed in 1978 to perform large-scale experiments with waves and coastal defence structures. The concrete channel measured approximately 233 metres in length, 5 metres in width, and could be filled with water to depths of around 9.5 metres. A wave generator installed at one end of the flume was capable of producing powerful artificial waves, allowing engineers to study the behaviour of dikes, breakwaters and other hydraulic structures under realistic storm conditions.

The Delta Flume formed part of the De Voorst research site, which had already been established in 1951 as an outdoor testing location for hydraulic models and water management experiments. At this site, researchers carried out many studies related to Dutch coastal protection and flood defence.

After decades of use, hydraulic research gradually moved to newer facilities. In 2015, the Delta Flume at De Voorst was officially taken out of service. Its research function was transferred to a modern Delta Flume built at the campus of Deltares in Delft.

Today, the remaining structures of the old flume can still be found in the forest area known as the Waterloopbos, where parts of the former hydraulic research installations have been preserved as historical monuments of Dutch water engineering.