Urban areas increasingly face flooding due to intense rainfall, as well as water shortages resulting from longer droughts. The current solutions are based on discharge and external supply, which are often expensive and not sustainable. How can we retain rainwater in the subsurface of urban areas longer and more effectively? And can we then subsequently make use of this water? This is what we are researching with different water managers, companies and institutes in the Urban Waterbuffer (UWB) project.
Water in city: a huge task
Urban areas increasingly face flooding due to intense rainfall and water shortages caused by longer droughts. The current solutions are based on rapid discharge and external supply, respectively. But these solutions are often expensive and unsustainable. Retention and infiltration in the city itself are necessary in order to absorb surpluses quickly, and retain them longer for subsequent use.
The Urban Waterbuffer: need to go deep
The space needed for water retention and infiltration in urban areas is typically limited, however. This results in conflicts with other above-ground uses of space, and in solutions that are expensive. With the Urban Waterbuffer (UWB), rainwater in urban areas could be purified and retained for longer, without obstructing other functions at ground level. The UWB uses deeper aquifers to infiltrate, store and extract rainwater through wells. The purpose of the project is to explore whether this system can make a significant positive contribution to preventing flooding and improving water supply in urban areas.
The project will study whether and how the Urban Waterbuffer should be applied in urban areas, and what its hydrological, chemical and financial impact would be. Four cases will be developed in more detail for Rotterdam, Rheden and the Hague. In two locations, test set-ups will then be built and monitored. The aim of the project is to quantify and document the potential of the UWB, and to translate the lessons from the first applications into realistic, clear application and design recommendations in a handbook. This can then serve as a guide for interested end-users, advisors and suppliers. A smart control system will also be developed for the control and monitoring procedures in the management of the UWB.
Urban Waterbuffer study extended to practice
Exploratory research has shown that a UWB can make a concrete contribution to the discharge of surplus rainwater and thus prevent flooding: UWB pilot projects will therefore soon begin in Rotterdam and Rheden.
During the first phase of TKI’s Urban Waterbuffer project, the location, the water balance, the preliminary design and the projected costs of actually installing a UWB were identified for four cases: Rotterdam-Spangen, Rotterdam-hNI, Rheden and The Hague. The results show that, particularly in the case of the targeted locations in Rotterdam and Rheden, a UWB could make a concrete contribution in the short term to the discharge of surplus rainwater and thus to flood prevention. The points requiring particular attention are the speed with which the peak precipitation loads can be infiltrated into the subsurface, and the pre-treatment of the rainwater with a view to preventing clogging.
The stored rainwater in Rotterdam would be used during dry periods as a source of high-grade freshwater to replenish a pond and to water artificial turf fields. It seems possible that these applications would cover a large part of the annual costs related to the depreciation, maintenance and management of the pre-treatment, infiltration and recovery. In Rheden, no use of the infiltrated water is envisaged for the time being, but potential benefits do exist in connection with the limited surface space required, and to the unburdening of the municipal sewerage system.
Work is ongoing in 2017 on the definitive design and the implementation of pilot systems in Rotterdam and Rheden. These will be monitored for their operation in practice within the TKI project.
Read more about this project on the Urban Waterbuffer website.