Flood risk is increasing due to climate change and the growth of the potential consequences of flooding. Analysing how flood-proof the spatial plan is, therefore becomes more important. Since most spatial planners have limited knowledge concerning flood risk, the Netherlands’ Directorate-General for Public Works and Water Management commissioned the creation of an instrument that can be used by planners to gain a better insight into the flood risk. However, this instrument is used inadequately. This research focuses on the question: What are design requirements for an instrument that helps to assess flood risk during spatial planning processes? And, what does this set of requirements mean for the design and use of the current MLS Explorer? This resulted in the findings that lead to a programme of requirements, the main findings were: (1) The best moment to use the Explorer is early in the spatial planning process; (2) The Explorer is most interesting for local government organisations such as municipalities and water boards; (3) The information that is presented must be understandable and useful, a list of information items is distilled from flood risk analyses that were found in the different case-studies; (4) Finally, the presentation format should be adjusted into a more visionary way to make the Explorer easier for spatial planners to use. On the basis of these results and the interview findings, a programme of requirements was compiled. The instrument should: 1. Be accessible and rapid to use 2. Provide understandable output 3. Be flexible 4. Be credible 5. Be easy to use for communication purposes and official planning documents 6. Provide sufficient information for a decent flood-risk assessment The current Explorer was assessed on these six requirements. Its overall score was insufficient, but the gap between the current version and the ideal version is not very large. The Explorer received the best score on the first and last requirements, since it is accessible (requirement 1) via the internet and it takes about 5 minutes to analyse one geographical area, and it presents sufficient information for a decent flood risk assessment (requirement 6). However, for the remaining four requirements, improvement is possible. The understandability (requirement 2) for spatial planners could be increased by using terms and figures that are commonly employed in that field. Increased flexibility (requirement 3) would serve two purposes: making the instrument more interesting for users with varying degrees of background knowledge, and making it more suitable for exploring an area by testing different scenarios. The Explorer’s credibility (requirement 4) should be improved by fixing bugs that make the instrument unreliable. The instrument’s suitability for communication (requirement 5) between parties at the beginning of the spatial planning process could also be enhanced. Such adjustments would facilitate meaningful conversations instead of first needing to wait for the release of research reports. Based on these requirements, this thesis gives a suggestions for a new design in order to give a concrete idea for adjustments that could improve the quality of the MLS Explorer.