Flood warning system in Denmark
(ProDeich 2024)
The project "Flood warning system in Denmark" develops an early warning system for floods originating from the sea. Severe storm surges in the recent past in Denmark have caused significant flooding and damages, and left an urgent need to better forecast these events. The Danish Coastal Authority (DCA), together with the Danish Meteorological Institute (DMI) was tasked to provide an overall flood warning system, including potential flood maps and dike breaches. DCA has therefore joined forces with Deltares in The Netherlands and justASK! in Belgium to develop a real-time flood warning system which can be triggered by water level and wind forecasts by DMI.
Objectives
The project aims to
- provide real-time predictions of flood maps and breach locations under storm conditions predicted by DMI;
- use a time-based approach considering rising and falling water levels during a storm;
- constantly updating simulations when new storm surge predictions are available (typically 6h intervals);
- base the calculations on potential failures of sea dikes considering all relevant failure modes;
- test and validate the predictions within two pilot sites, one at the East coast (validation using data from the storm surge in 2023) and one at the West coast (using data from the storm surge in 1999).
Methodology
The flood model used in this project is the SFINCS/SNAPWAVE model by Deltares. This model was complemented by the ProDeich model from justASK! for the calculation of dike safety and potential breaching. The input for both models comes from DCA providing the bathymetry and topography of the dikes, segmentation of the dike lines, and additional information such as soil drill information and information about any special observations at the dike line (so-called points of interests = POI). Running both models as indicated in the workflow here results in a fast method to predict flood maps and potential breach locations.
Role of justASK!
justASK! collaborated with DCA and Deltares on the setup of the methodology, the development of the calculation methods, and performing the failure mode and breach calculations. All dikes in Denmark are split in segments and sections, depending on various criteria related to the geography and cross-sectional details of the dike, but also the geotechnical information from the soil drills and the hydrodynamic boundary conditions.
What can justASK! do for you?
justASK! can perform assessments of coastal safety using a fault tree and failure mode approach for coastal structures. This is independent on which type of coastal defence is in place (e.g. dikes, breakwaters, dunes), but can also be done if no structures are in place (e.g. beaches, cliffs). We will use either deterministic or probabilistic approaches, depending on the requirements and requests of our clients, but also depending on the data available and tools which have been used in the past.
justASK! will assist in the overall analysis of the coastal area(s). Using all available data (water levels, tidal information, storm surges, bathymetry, and topography, etc.), we can provide you with up-to-date information about the safety of the coastal areas you are interested in. We can also re-design or propose adequate measures in case the safety assessment delivers insufficient degrees of safeties. JUST ASK!