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Floods are one of the natural disasters not preventable, affecting people and causing significant damage to economic activities and infrastructures. Thus, it is of foremost importance to, within a disaster risk-reduction strategy, develop a useful flood forecast and alert system to prevent people from suffering flood disasters and mitigate its consequences. This article presents the Flood Forecast and Alert System in operational mode since 2019 for the Águeda river basin located in Portugal’s centre region. This system is technologically advanced, differing from others since it uses a coupled real-time hydrologic and 2D hydrodynamic modelling supported on numerical weather prediction and a high-resolution digital terrain surface model. The system components are automatically activated and linked: i) a rainfall forecasting model (WRF), ii) a hydrological model (HEC-HMS), iii) a hydraulic model (HEC-RAS 2D), and a iv) Web-GIS platform. The hydrological model is forced with forecast precipitation for the next three days and updated every 6 h, which is crucial to generate pre-flood hazard maps. It also includes a Web GIS service for flood hazard dissemination available for civil authorities and citizens. A flood forecast and alert system is highly relevant to the community since, by enhancing knowledge, it provides the authorities responsible for assessing and managing the flood risk, responsiveness to disasters and timely decision-making, which is even more evident in the context of climate change.

Over the last few decades, we witnessed a revolution in acquiring very high resolution and accurate geo-information. One of the reasons was the advances in photonics and LiDAR, which had a remarkable impact in applications requiring information with high accuracy and/or elevated completeness, such as flood modelling, forestry, construction, and mining. Also, miniaturization within electronics played an important role as it allowed smaller and lighter aerial cameras and LiDAR systems to be carried by unmanned aerial vehicles (UAV). While the use of aerial imagery acquired with UAV is becoming a standard procedure in geo-information extraction for several applications, the use of LiDAR for this purpose is still in its infancy. In several countries, companies have started to commercialize products derived from LiDAR data acquired using a UAV but not always with the necessary expertise and experience. The LIDAR-derived products’ price has become very attractive, but their quality must meet the contracted specifications. Few studies have reported on the quality of outsourced LiDAR data acquired with UAV and the problems that need to be handled during production. There can be significant differences between the planning and execution of a commercial project and a research field campaign, particularly concerning the size of the surveyed area, the volume of the acquired data, and the strip processing. This work addresses the quality control of LiDAR UAV data through outsourcing to develop a modelling-based flood forecast and alert system. The contracted company used the Phoenix Scout-16 from Phoenix LiDAR Systems, carrying a Velodyne VLP-16 and mounted on a DJI Matrice 600 PRO Hexacopter for an area of 560 ha along a flood-prone area of the Águeda River in Central Portugal.