Due to climate change, cities are expected to become subject to increasingly intense heat waves and precipitation. This calls for them to become more resilient towards such fluctuations. Green infrastructure is increasingly acknowledged as a means to enhance climate resilience, but cities – especially city centres – often lack the necessary space for realising such infrastructure. That is why green, vegetated roofs are frequently promoted as a potential solution for this spatial problem. This is also the case in the city of The Hague. In this municipality, green roof development has been stimulated for years with subsidies to increase the resilience towards the urban heat island effect (UHI) and stormwater flooding (SWF).

But while there is consensus within the municipality that more green roofs should be realised, no clear, quantifiable targets are set to achieve specific resilience goals. In part, this is because the potential benefits of green roofs have not been quantified at the city scale. And while most local benefits of green roofs are well known, downsides, costs and the barriers to implementation are not well understood.

The goal of this study is to examine the extent to which green roofs can increase climate change resilience in The Hague. In order to view this matter from complementing perspectives, three methods are used to answer five sub-questions. These methods are spatial analysis, financial cost-benefit analysis and stakeholder interviews.

In conclusion, large scale realisation of extensive green roofs is likely to have a positive effect on climate resilience in The Hague. These effects are significant at the city scale if green roofs are realised in large quantities, but they will likely not lead to easily noticeable results for the average citizen on the street. Substantial economic, political, legal and social barriers need to be overcome to implement green roofs at city scale for public environmental benefits. Several areas in the city do however hold notable potential to use its roof space for increased climate resilience.

With a global trend towards urbanisation, the resilience of humanity against economic, social and environmental challenges increasingly shifts from rural to urban areas. Where green and blue infrastructure are expected to mitigate some of the impacts of heat waves or storm events for the urban environment, current assessment methodologies to prove so are lacking. To illustrate the viability of urban Nature-based solutions as alternatives to existing grey infrastructure, this research first looked into assessing the benefits of 4 urban ecosystem services (ES), namely Urban Cooling, Stormwater Runoff Catchment, Carbon Storage and Coastal Protection services. With The Hague as the area of interest, the research was successful in demonstrating positive impacts towards climate resilience for each of the 4 studied ES. First, the presence of urban natural infrastructure was shown to reduce the urban heat island effect by up to 1.5 °C. Green urban areas were further revealed to catch over 50 % of stormwater runoff for major storm events as well as being responsible for the majority of urban carbon storage. Lastly, coastal forests and dunes were proven to be a contributing reason in keeping the overall coastal exposure risk towards inundation and erosion at low to moderate levels. While the initial results of the ES analysis speak for themselves, further evaluation of the employed methodologies revealed major concerns in terms of output consistency and transparency between different tools, such as InVEST and Natural Capital. As the outputs of seemingly analogous models varied greatly and a certain obscurity towards methodological background processes persisted, the results of urban specific assessment models of current ES mapping and evaluating tools require further validation in order to be universally acceptable. The conclusion of this study can help advance the inclusion of urban nature-based solutions into urban policy and planning exercises, while simultaneously raising awareness towards the need for further development of common urban specific ES assessment methodologies.