The past few years have seen the raise of unmanned aerial vehicles (UAV) in geosciences for generating highly accurate digital elevation models (DEM) at low costs, which promises to be an interesting alternative to satellite data for small river basins. The reliability of UAV-derived topography as input to hydraulic modelling is still under investigation: here, we analyse potentialities and highlight challenges of employing UAV-derived topography in hydraulic modelling in a tropical environment, where weather conditions and remoteness of the study area might affect the quality of the retrieved data. We focused on a stretch of the Limpopo River in Mozambique, where detailed ground survey and airborne data were available. First, we tested and compared topographic data derived by UAV (25 cm), RTK-GPS (50 cm DEM), LiDAR (1 m DEM) and SRTM (30 m DEM); then, we used each DEM as input data to a hydraulic model and compared the performance of each DEMbased model against the LiDAR based model, currently used as benchmark by practitioners in the area. Despite the challenges experienced during the field campaign-and described here-, the degree of accuracy in terrain modelling produced errors in water depth calculations within the tolerances adopted in this typology of studies and comparable in magnitude to the ones obtained from high-precision topography models. This suggests that UAV is a promising source of geometric data even in natural environments with extreme weather conditions.

Floating foundations in concrete for wind turbines offshore is a concept which up till now have limited use in full scale applications. Currently, the Hywind Tampen project is the only executed project with concrete substructures and multiple structures in a commercial setting. Serial producing such foundations require new ways of thinking, modified methods and re-thinking of conventional design and construction processes. Results presented highlights the differences compared to conventional construction and points towards future developments and improvements using the Hywind Tampen project as a basis. Construction of spar type substructures requires a combination of partly construction onshore/in dry dock and partly construction in a deepwater site and the concept, design and methods must accommodate the method of construction. For serial production material flow, progress and logistics becomes vital. The serial production developed and used for the fabrication of Hywind Tampen concrete substructures proved to be a success, but we need to take into consideration that is a small-scale production compared with large offshore wind developments. The use of slipforming technique is an efficient and robust method for constructing watertight hulls and planning and adoption of this technique for serial production has been done successfully. Concrete substructures have been used for the offshore oil & gas fields since late 1960's and the knowledge and experience from design and execution methods has been implemented in offshore wind in parallel with developments required for a new industry and serial production. Further development of floating substructures for offshore wind relies on contractors being able to fabricate fast, cost-competive and reliable foundations in a safe manner and within quality requirements for offshore structures. The Hywind Tampen project represent an international milestone in this respect, being first of its kind project within floating wind. There are multiple floating wind concepts on the marked but there is only one completed project worldwide where learnings and experience can be utilized for future developments, Hywind Tampen.