# Multi-Hazard WebGIS Platform for Coastal Regions
## 1 Introduction  
Coastal zones are exposed to multiple hazards that are being exacerbated by climate change [1, 2, 3, 4]. Flooding resulting from the combination of energetic wave conditions, storm surges and high spring-tide levels is one of the major hazards affecting coastal zones, whose impacts will increase in the future [5, 6]. The type and extent of the impacts will depend on the territorial and morphological characteristics of the coast (e.g., wave overtopping of coastal structures and avalanche, overwash and breaching of dunes). Coastal erosion generated by highly energetic events can result in the retreat of the coastline, increase of the runup and the overtopping discharge and consequently the increase of the impact of inundation. The concentration of people and assets along the coastline increases coastal vulnerability and contributes to very severe consequences ofthese natural events that are being exacerbated by climate change effects either through sea level rise or increasing storminess [7,8]. Emergency response and long-term planning of coastal interventions and occupation require a combination of real-time information (data and forecast results), aggregated along with the relevant key factors, and risk indicators that highlight the vulnerability of each coastal stretch to the combinations of hazards that lead to severe conditions. Computational frameworks and their associated interfaces have been developed over the last two decades to address flooding issues (e.g., [9, 10, 11]) or multi-hazard predictions. The Water Information Forecast framework-based platforms [12], dedicated to multiple hazards, are an example of the latter, addressing floods [12], oil spills [13], fecal contamination [14] and biogeochemical evolution due to anthropogenic and climate changes [15]. These types of instruments are at the core of nowadays support flood tools for coastal managers and civil protection agencies, gathering the relevant data and forecasts, and making them available in a user-friendly way (e.g., [16,17]). However, several limitations remain in existing tools:  
* They are often dedicated to a specific site, developed around particular conditions and data streams. While frequently tailored to specific needs, their maintenance is complex and time-consuming, and often become obsolete, not resisting the advances of technology. Moreover, their application to similar systems is so time-consuming that development from scratch is commonly the solution undertaken for new deployments. * They are not designed to address multiple hazards and multiple sources of data. For systems subject to several flooding hazards sources, an integrated and individual analysis is required and the data that best fit this analysis needs to be included. * Technological constraints often hamper the usability of these platforms, making for instance the visualization and probing over the complex space- and time-varying information frequently too slow. Usually, inadequate and static designs prevent the adaptation to multiple uses (e.g., platforms tailored for management or for civil protection agencies have different requirements) and the necessary evolution to address new challenges (e.g., addressing the impact of a new construction in the area). To address these challenges, a WebGIS multi-hazard platform, hereafter referred to as MOSAIC platform, named after the project that supported it, is presented here. It aims to support the implementation of an innovative flood risk management framework for coastal zones. The platform's framework is supported by observatories that integrate real-time monitoring data, from both in-situ and remote sensors, and predictive numerical models addressing both coastal hydrodynamics and morphodynamics in order to predict wave overtopping of dunes and coastal structures.