In this study an overview of existing and planned storm surge barriers in the world is provided. A systematic analysis relates functional requirements (e.g. navigation and tidal exchange) to the main barrier characteristics (e.g. gate type, dimensions). Furthermore, as the costs of barriers are an important issue in the planning, available cost information is analyzed and related to main barrier characteristics. An approach to provide a preliminary cost estimate of new barriers is presented. Finally, some critical technical challenges are discussed and related to functional requirements and boundary conditions. Overall, the results of this study can assist in the initial design and planning phase of storm surge barriers for new locations.Keywords: storm surge barrier, coastal structures, flood risk, coastal protection. INTRODUCTIONHuman population in coastal zones is exposed to a variety of natural hazards such as erosion, salt water intrusion, subsidence, tsunamis, and floods resulting from both storm surges and high river runoff (Small and Nicholls, 2003). However, due to climate change induced effects, such as sea level rise, the likelihood of natural hazards will increase, making these areas more vulnerable. Moreover, coastal zones are associated with large and growing concentrations of human population, settlements and socio-economic activities (Small and Nicholls, 2003), intensifying their vulnerability. From an economical perspective these conditions lead to a higher demand for safety and a corresponding substantial investment in improving flood protection (Van Dantzig, 1956;Brekelmans et al., 2012). Furthermore, flood protection standards are expected to increase with enlarged prosperity (Hallegate et al. 2013). It is therefore expected that in coastal regions around the world governments will continue to invest more in coastal protection.In areas with large bays, estuaries or coastal waterways with adjacent flood defenses, constructing a barrier can be a suitable option to protect coastal zones. This type of solution is often chosen as a preferred alternative, when the required length of dike strengthening behind a barrier is significantly reduced (Jonkman et al., 2013). This measure can shorten the exposed coastline, and subsequently reduce the costs and hindrance of dike improvement in densely populated areas. In addition the construction time required to improve the dikes can be shortened considerably (Rijkswaterstaat, 1976).Although several types of barriers (e.g. closure dams, tidal barrages and storm surge barriers) exist, storm surge barriers are mainly considered as a future intervention for more developed and prosperous regions, such as many coastal cities. In such regions preserving ecology or maintaining navigation have a large value and the high costs of storm surge barriers compared to the alternative type of barriers can be afforded. For example, storm surge barriers are currently proposed at Houston, USA (De Vries, 2014); New Orleans, Mississippi, USA (van Ledden et al, 2012), New York, U...