In the Netherlands, the frequency and severity of extreme rainfall events are expected to increase. This can result in severely detrimental effects. It is complicated for municipal actors to effectively manage these events, as it requires judgement on probabilities, costs, and uncertain impacts. As a result, obtaining scientific knowledge through climate tools and model results has become increasingly important in informing policy-making processes. While model results and climate tools have been shown to create an imperative to act for municipal actors, a clarification of how a certain approach might offer support in a specific context is scarce. By simplifying model simulations for municipal actors, information gets lost and becomes (unconsciously) framed, leaving room for the personal interpretation of municipal actors. Framing can change the actor’s perception without altering the scientific information they were initially provided, which might result in different decisions taken on water management. Decision-making is not an individual process. It involves interaction between a multitude of stakeholders of various disciplines, all with own individual contextual factors. It is essential for effective decision-making on extreme rainfall events that interaction is well-coordinated.

This integrated master thesis for the master’s degrees in International Land and Water Management and Communication Design for Innovation, therefore, aims to explore the influence of visually framed extreme rainfall model results on the interaction between municipal actors. This is explored in the Municipality of The Hague and the Huygenspark neighbourhood. The model results have been adjusted to two contrasting frames: in terms of gains or losses and psychological distant or near impacts.

These two contrasting frames have resulted in the development of four visually-framed extreme rainfall model results, hereafter named maps. For the distant loss map, water nuisance has been assessed in the Tygron Geodesign Platform. The water nuisance map shows that especially the Stationsweg, the tunnel at the Rijswijkseweg, and the tunnel underneath the train tracks will have water nuisance issues during extreme rainfall events. For the near loss map, the framing of adaptation tipping points has been applied. Adaptation tipping points frame the issue from the socio-political objectives and show the moments in time at which a change in the current management strategy no longer meets the municipal actors’ objectives. The socio-political objective has been identified to focus on maintaining the accessibility of roads for cars and ambulances. The model shows that the Stationsweg and the tram tunnel cross this threshold during a once a 25 years rain shower (40 mm/hour), while the Rijswijkseweg tunnel reaches the threshold already at a rain shower of less than once a 10 years (30 mm/hour). This return period will become more frequent to once every 13 years and an unspecified low non-extreme return period in the upper scenario of 2050 respectively. The two main chances to tackle this issue are either spatially, in the Oranjeplein and Huijgenspark or through adaptation mainstreaming opportunities.

The four maps were interpreted by fourteen municipal actors within the Municipality of The Hague through semi-structured interviews. Visual framing was found to have a profound effect on the interpretation of municipal actors. The near-framed adaptation tipping points map made the issue more concrete and expressed urgency as well as the necessity to take action compared to the distant-framed water nuisance map. The chance maps created a more positive interpretation than the loss maps. Besides, the interpretation of maps was also determined by the pre-existing knowledge structures and ways of looking at the issue, resulting in three distinct interpretations for the adaptation tipping points map. While every map has its own main interpretation, most municipal actors emphasised that the maps should be combined to create an overall story. This story can be used during interaction to convince others, but it can also be to start a discussion or to weigh different options. The visual maps can, therefore, be seen as a ‘story support tool’ for interaction.