SandBox-FM: Augmented reality CFD Hydraulic engineering and education through collaborative modeling Willem Ottevanger 1 , Robert-Jan den Haan 2 , Fedor Baart 1 , Pieter Visser 1 , Jurjen de Jong 1 , Bas van de Pas 1 , Cindy van de Vries 1 , Cilia Swinkels 1 , Arjen Luijendijk 1,3 1 Deltares, Delft 2 University of Twente, Enschede 3 Technical University of Delft Abstract The SandBox-FM is an innovative collaborative modeling tool. It offers the possibility for various stakeholders to interact with a real time hydrodynamic computation by adjusting the model geometry in the sand. The impact on the hydrodynamics are visualized instantly, which contributes to system understanding, enhances communication between stakeholders and ultimately could affect the decision making process. This extended abstract presents the design, lessons learned and an outlook of future plans of the SandBox-FM. Introduction The advance of computational power since the 1980’s has led to great technological developments. In hydraulic engineering, it is currently possible to predict hydro- and morphodynamics for decades using advanced computational models. Such models have proven to be very useful during the design phase of hydraulic measures. However, the use of complex computational models also shows limitations during the design process, particularly when part of a multidisciplinary decision making process with many stakeholders from various backgrounds. The limitations can be identified as follows:  A computational model requires an expert modeler, this might limit the possibility of stakeholder input.  The complexity in the model setup limits the number of iterations in design processes.  Many stakeholders are not familiar with computational models and unable to interpret the model results correctly.  Models lack interactivity.  The building of models has a steep learning curve for new users, like students. The objective of the current research is to develop a participatory tool which allows stakeholders to interactively design hydraulic measures. The tool should therefore (1) create a lower threshold to engage with models; (2) calculate designed measures in a shorter period of time; and (3) present results in a manner which is easier to understand by all stakeholders. Ultimately, the tool should contribute to establishing more accepted designs or a shorter design process and it should reduce the learning curve for students so that they can focus on the research they set out to do. To that end, we developed the hybrid physical-numerical model, named “SandBox-FM”, as a tangible user interface combined with either a Delft3D-Flexible Mesh (FM) or an XBeach model. In this extended abstract, we focus on the design, lessons learned, current limitations and share an outlook of future plans. Background and related work Similar to computational power, computer interaction has evolved drastically in the last decades. One recognized way to facilitate easy, intuitive and low-threshold interaction with digital information such as models is through tangible user interfaces. The main principle behind such interfaces is to provide physical forms to digital information. These physical forms serve as both control and representations for their digital counterpart. This way, tangible user interfaces make use of people’s ability to grab, move and change physical objects or materials.