Flood forecasting Parramatta

Parramatta is the main business district of Greater Western Sydney (Australia). Located 23 kilometres west of Sydney’s central business district, it is the place for growth and long-term prosperity for both businesses and residents.

But when the clouds burst, the Parramatta river can cause flash floods in the City of Parramatta. Heavy rainfall rushes down the slopes of the surrounding Blue Mountains. Within hours water levels in the Parramatta river can rise to 30 feet threatening the central business district.

Enough lead time to anticipate and save lives is key with these types of flash floods. Traditional early warning systems and hydrodynamic simulation software lacked speed and accuracy to deliver the information to the Parramatta council and state emergency service on time. For the City of Parramatta Royal HaskoningDHV developed, in partnership with Nelen & Schuurmans Consultancy, the Flash® state-of-the-art early warning service based on 3Di hydrodynamic simulation software.   Nelen & Schuurmans Consultancy has a long standing experience in flood forecasting and information systems. The Flash® early warning service created a connected, resilient community and minimises the impact of flooding for the City of Parramatta.

The Flash® service uses meteorological forecasts, water level and rain gauge monitoring data and a 3Di hydrodynamic model to create a warning service that is based on the impact of expected rainfall. The system calculates every 30 minutes multiple scenarios to assess the probability of (flash) flooding.

To make this possible data engineers built a connection with the Bureau of Meteorology to import their advanced and detailed precipitation forecast (STEPS). Water level and rain gauge monitoring data is imported from the City of Parramatta. This is fed to an 3Di hydrological flood model to calculate the effects of the expected rainfall on the water levels in the river and expected flood scenarios.

The flood scenarios are used to create maps that provide the early warning system with water depths, flood hazards and arrival times. Based on these maps alarms are triggered when a flood is expected. Once alarms are triggered, the flood simulations are automatically stored for evaluation and for the system to learn from the event. To provide the information at the right time and in a user friendly format a custom-made dashboard is developed, which is  called the ‘Floodsmart dashboard’. In one glance the end user can understand the current situation and possible developments in the next 12 hours.