Historically, major storms, the associated storm surges and rainfall have posed the biggest threat to life and property around coastlines and along rivers. However, in the age of global warming and accompanying sea level rise the confluence of several risk factors creates a new set of hazards, and a different overall approach to flooding protection is required. The combination of higher sea level and warmer atmosphere leads to a new reality where even minor storms carry a risk of serious flooding. Similarly, the co-occurrence of heavy precipitation leading with high sea levels, known as compound flooding, can affect cities located at river mouths. In addition to flooding, traditional coastal problems such as sediment erosion, saltwater contamination and chemical spills are complemented by emerging issues such as microplastics and biohazards.
While traditional wave forecasting provides average wave conditions near the coast, future climate conditions will call for operational phase-resolving wave modeling to furnish more detailed forecasts to provide a complete picture of potentially hazardous conditions. Monitoring of water quality and dispersion of pollutants must be based on a more detailed picture of river and estuary dynamics, requiring systematic use of multi-physics modeling as well as resolution of flow problems on ever larger domains. Furthermore, as the frequency and severity of flooding in coastal and riverine urban areas increases, new models must be developed which incorporate phenomena such as floating debris and interaction with the urban grid.
RESCUER integrates four research themes:
WP1: Coastal modeling and hazards focuses on phase-resolved wave forecasting tools such as shallow-water and Boussinesq models, and the study of wave processes and hazards related to infragravity waves and waves propagating over steep bed topography.
WP2: River and estuary dynamics focuses on flow and sediment transport in the river/estuary contact area, and to study sediment transport over saturated subsurface flow.
WP3: Urban flooding focuses on the construction of models which include floating debris and interaction with the wastewater system.
WP4: Water quality focuses on the spreading of pollutants and the kinetics of decomposition.
WP1 advances operational, phase-resolving nearshore wave forecasting and wave-driven hazard prediction by combining (i) physics-focused studies of long-period and infragravity dynamics over complex/steep bathymetry, (ii) numerically robust and well-posed discretizations and boundary conditions for dispersive and hyperbolic wave models on complex decompositions, and (iii) computational and workflow enablers that move phase-resolving modelling toward operational use. Across the employed fellows in the Doctoral Network, progress spans controlled modelling building blocks, benchmark and field-driven validation pipelines (laboratory refraction/diffraction and runup benchmarks; infragravity-relevant pressure datasets and campaigns), and downstream coupling readiness to urban flood and estuary/river impact models, enabling coherent end-to-end hazard chains from nearshore wave transformation through run-up/overtopping toward inundation and estuarine response.
The main objectives of the WP2 include the development of accurate, robust, and fast numerical models based on the recent developments: Modelling impact of waves and tides on river mouth and river; study of coupled surface water flows over erodible beds with variably saturated subsurface flows as well as dry and wet granular flows, characterization of pollutant transport upstream and downstream. Tasks include the setup of suitable laboratory experiments for the validation of numerical models for river flow with and without movable bed, development of more efficient numerical scheme for river flow coupled with erosion and subsurface processes benchmarking of the numerical models using experimental activity and coastal flow case study and analysis of the new difficulties associated to real environments with respect to test case flow modeling case study.
WP3 sets out a comprehensive framework for advancing the modelling of urban hydrodynamics. The objectives and tasks defined for WP3 describe the long-term vision that the consortium aims to achieve by the end of the project. They encompass the development of improved numerical methods capable of resolving urban flow processes with higher accuracy, the simulation of the transport and interaction of large floating objects, such as vehicles or debris, and the representation of the hydraulic influence of complex underground networks including sewer systems and natural cavities. WP3 also aims to extend modelling capacities to more intense phenomena such as debris flows and mudflows, which increasingly threaten urban areas during extreme rainfall or rapid snowmelt. Complementing these numerical developments, WP3 foresees the design and implementation of dedicated laboratory experiments to provide robust validation data under both idealised and realistic conditions, including configurations with moving objects, obstacles, and openings. A key component of WP3 is the establishment of a modelling chain that links river and coastal processes to the hydrodynamic behaviour within the urban environment. Finally, WP3 includes a benchmarking phase in which the numerical models developed within the consortium will be tested against detailed field data from the Senigallia site and other real-world datasets. Taken together, these activities represent the full scope of the objectives and tasks that WP3 will pursue over the lifetime of the project.
The main objective of WP4 is to develop mathematical models to be able to study, track, and better predict the migration and settlement of pollutants in water systems, namely:
1. Assessment of surface water interaction and pollutant dispersion between urban watershed, canals, and coastal flow.
2. Mixing and pollutant transport in the surf-zone.
3. Investigate/validate by laboratory experiments the compound behavior at hydrodynamic conditions.
The work addresses the need for reliable numerical tools capable of predicting pollutant transport and transformation in aquatic environments. Methodological approaches are being defined according to data availability and quality, supporting the development, calibration and validation of an integrated hydraulic and biochemical model capable of simulating the complete urban river–estuarine–coastal water system, including flow dynamics and water quality processes.
