- 23rd March 2018
- Posted by: Joanne Woodhouse
- Category: Projects
New flood defences are planned for Ireland’s second city – Cork. The scheme depends on flood storage in two hydropower reservoirs upstream. Hydro reservoirs are most efficient when full, so several days’ notice of a flood event is needed to create the necessary flood storage.
Our challenge was to develop operational procedures for the reservoirs and develop a forecasting system that could predict large events with the required lead time – around five days. The system also had to simulate the drawdown process and the effect of the operational procedures on upcoming events.
A Delft-FEWS based forecasting system for the Lee catchment was therefore developed. We currently host the system for the Office of Public Works using a Cloud Provider (AWS). The system couples rainfall runoff models with an ‘intelligent’ flow routing model that implements the operational procedures.
Respecting the physical and safety constraints of the reservoirs’ operation and their gates using a mixture of probabilistic and deterministic rainfall inputs, the system issues clear guidance on how to manage a flood event.
Testing using 10 continuous years of archived forecasts (every 12 hours) have shown the system correctly simulates control drawdown and releases during that period. Operators from Cork City Council, the Electricity Supply Board (ESB) and the Office for Public Works have been trained to use the system by simulating past floods.
Forecasting models were developed and tested using our HyDB software – which integrates with Delft-FEWS. The same model network was also used to get design flows for the scheme using a long rainfall series generated by a stochastic rainfall model. HyDB also managed that process.
Probability Distributed Model (PDM) is used for rainfall runoff modelling, Flood Modeller for flow routing. Rainfall forecasts are from Met Eireann and the European Centre for Medium Range Forecasts.
Forecasts faithfully implement the complicated control rules and constraints used to limit flows in Cork City and reservoir operators are supported in their decisions. The system gives clear recommended actions and is fully tested using real rainfall forecasts.