The Rainproof City

Circular Solutions

City design in the Netherlands is based on current climate conditions and does not account for climate change. Due to climate change, rainfall intensities are expected to increase. Therefore, the urban water system should be designed in such a way that the extremer events of the near future do not cause significant damage.

In the Netherlands pluvial flooding is in most cases prevented by the municipality by implementing drainage systems in public space. In general drainages systems are designed such that rainfall events up to 20mm should not cause any damage. These rainfall events were estimated to occur once every 2 years. In recent years we have seen multiple rainfall events with intensities that were much higher than this normative rainfall event. This has led to the awareness that we should design our drainage systems and also our land surface such that these extreme events do not cause significant damage. Due to climate change rainfall intensities are expected to increase.

Design principles in the Netherlands are based on current climate conditions and do not account for climate change. Although existing water systems are designed to be robust, increased extreme storms (frequency as well as magnitude) may be expected to increase damage due to flooding, both in magnitude and frequency. Solutions can be found in redesign of the drainage systems but this may come with considerable costs. Therefore also reshaping the public space should be considered to increase the capability of storing water in such a way that damage is kept to a minimum. It is interesting to realize that, although frequently stated in the past, only now, since extreme storm events are more probable to occur, spatial planning and water management become really interdependent. The question is how to deal with that fact in a optimal way. Optimal in the sense of cost effective, but also in the way various stakeholders including citizens and their properties are involved.

Precipitation falls both on private property and on public space. Rainfall that falls on roofs as well as on paved gardens is drained directly by the drainage system. It could be argued that citizens can help to prevent pluvial flooding by implementing storage measures on their property. But this first of all requires so called water awareness of citizens. This study will demonstrate the effect of interactive modeling on a high resolution to determine the effect of small scale measures (on the scale of private property) and shows a way to build the required water awareness. Both are presented in the form of a case study for the Buiksloterham, a redevelopment area in the city of Amsterdam.

Source: Adaptive Circular Cities - The Rainproof City 

Brolsma, R., van Leeuwen, E., & ten Velden C. (2016). Circular Solutions: Part III: the Rainproof City. TO2 federatie. 

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