Redesigning urban water systems and exploring synergies Lessons from an urban planning perspective on the 'Rotterdam Water City 2035' vision and follow ups 2005-2016

This study addresses two main topics. The first one is to describe the Rotterdam Water city 2035 approach, a systemic water approach for Rotterdam dealing with storm water and at the same time exploring synergies to improve quality of life. The second topic deals with the question if the approach was successful as well as what lessons can be learned from this. Polders and the inverted urban landscape The city of Rotterdam is built on the riverbanks of the river Maas and river Rotte, in elevation, just above sea level. With some exceptions, the North and Eastern part of the city is built into many different kind of polders below sea level. Over the course of some 800 years the drained peat beds subsided to lower levels. Nowadays the western part of the Netherlands consists of a patchwork of either, different kind of polders below sea level originating from different eras, in different seizes with either peat or sea clay, or, (former) riverbeds above the surrounding landscape (fig.1). The sandy riverbeds did not subside. This is called the inverted landscape! The central area of the city near the banks of the river Maas and the port are the highest grounds in the city! Challenges and Aims With a changing climate, natural water cycles are also influenced. As a delta city, Rotterdam had already to deal with water issues coming from all sides. Yet due to climate change the extremes of discharge and precipitation are becoming bigger (fig.2). More river discharge is expected as well as sea level rise. These are issues which are addressed at national and local level such as in the national Room for River program and others. This is not part of the scope of this study. In the area studied there will be more peaks in precipitation which means more rain showers which will release more water than average this is alternated with periods of no or little rain (KNMI, 1999). Over the years more storage capacity to store rain water was and is needed in the city. Van der Brugge et al. (2010) mention that for the Rotterdam region, 600.000 m 3 of extra water retention is needed before