In 1996 the Dutch Department of Transport, Public Works and Water developed a program called ‘Roads to the Future,’ and a component of this project was the testing of a pilot floating road. The testing of the pilot took place in 2003 and aimed to create a 70 meter stretch of road in the town of Hedel, the Netherlands to mitigate against rising ground water levels. The floating road was designed to maintain access and flexibility in traffic and movement and prevent the isolation of a village otherwise cut off by flooding.
The ‘Floating Roads’ pilot project was implemented in Hedel in the Netherlands. The town of Hedel is prone to flooding due to increasing ground water levels which can lead to the isolation or cutting off of the village and impeded traffic flow. The floating road was designed to be some 70 meters in length and withstand vehicles travelling at speeds of up to 80mph. The town of Hedel in the Netherlands has some 5,000 inhabitant. The small size of the town and the infrastructure of the floating road meant that local authorities and government were central to its planning and implementation.
The design and construction of the road consisted of standard linked units made of aluminium and filled with polystyrene foam to facilitate ‘floating’. These flexible links were secured into the river bed using steel piles and the top layer of the road itself was constructed using typical concrete and non-flexible materials. Aluminium was chosen as a lightweight material that requires little maintenance and is recyclable. Moreover, the standardized units allow for easy transportation and replacement, if necessary. The links between the units provide enough stiffness but also flexibility to withstand changing water levels. The innovative element of the design was the attachment ramps on either end of the floating road. The attachment ramps were stiff structures designed to withstand movement but implemented with a further safety option of a remote controlled moveable bridge should water levels change abrubtly.
The floating road was tested using a normal vehicle under both regular conditions and with incoming waves. The structure performed as expected and the driving experience of the vehicle pilot was not affected by the moving water below. In a simulation test of an emergency situation, a breakdown vehicle went through the same tests and the floating road performed successfully.
Cost-effectiveness and ecosystem-based aspects
Floating and elevated roads are alternatives to bridges and tend to be less expensive. Once constructed, they do not require more maintenance than other types of roads. They are, however, a significant piece of infrastructure and therefore the cost and investment may only be returned once flooding has occurred and been mitigated against.
Floating roads take up less space in terms of construction and infrastructure than traditional roads. They also sit on top of groundwater and therefore do not disturb natural flows and therefore also are likely to minimise pollution.
The main question posed in the pilot construction of the floating road was to understand whether there was added value in having floating roads over conventional roads in order to solve traffic problems that ensue amidst extreme flooding and changing groundwater levels. Floating roads were found to be functional in Hedel and also reduce the amount of disturbed space compared to other options such as a traditional road. For example, generally a road floating on groundwater is 20 meters wide whereas a traditional road at one meter above ground level is 45 meters wide. Cost-efficiency was also considered advantageous to that of building a bridge.