Design and testing of a real-time flood forecasting system for urban catchments

Abstract

In the late afternoon on Friday 9 March 2001, a severe storm occurred on the south side of Brisbane. Peak intensity reached more than 210 mm/h, and total rainfall up to 200 mm occurred over a period of 3 hours. Extensive flooding was recorded at a number of locations in the Norman Creek catchment. This and other localised storm events have highlighted the need for real-time flood forecasting to increase the awareness of and preparedness for flash floods in urbanised areas, and to minimise the damage and disruption as a result of flash floods in the tropical and sub-tropical environments. A real-time forecasting system is developed using ensemble probability-based rainfall forecasts coupled with an efficient raster-based hydrologic model to forecast water levels at critical locations for dissemination on the internet. Forecasting of flash flood involves interrogating ALERT/telemetry data on gauge rainfall and water levels in the catchment, processing and interpreting radar scans to determine the storm’s spatial structure and movement, numerical weather prediction up to 30–90 min into the future, generating multiple realisations of likely rain fields, predicting multiple hydrographs from forecast rain fields, and converting hydrographs into probability-based water level forecasts at critical locations in the catchment. The design is critically constrained by the requirement to update the forecast on the internet every 15 minutes. The paper reports a retrospective test using the gauge and radar data for the March 2001 event in the 28 km² Norman Creek catchment.

Keywords:

• Rainfall and flood forecast
• weather radar
• GIS
• RAMS

Additional information

Notes on contributors

B Yu

Bofu Yu is a professor and Deputy Head of the Griffith School of Engineering in Brisbane. Over the past 20 years, he has worked on rainfall-runoff modelling, extreme rainfall and rainfall erosivity, and soil erosion and sediment transport. More recently, he has been developing a raster-based framework to integrate dynamic rain fields with runoff and sediment generation algorithms at a range of spatial and temporal scales.

A Seed

Alan Seed is a senior research scientist at the Centre for Australian Weather and Climate Research, Bureau of Meteorology, working on quantitative radar rainfall estimation and short-term rainfall forecasting. His undergraduate degree was in civil engineering at the University Natal, Durban, South Africa. Alan worked as a hydrologist before moving to Canada to undertake a PhD at McGill University, Montreal, completing his thesis on radar rainfall estimation and space-time statistics of rainfall in 1989. After returning to South Africa to work on developing flood warning systems, Alan moved to Auckland to work at the Physics Department, Auckland University, to work on radar observations of orographic rainfall in the Southern Alps. He joined the Bureau of Meteorology in 1997 as a research fellow in the Cooperative Research Centre for Catchment Hydrology, and has undertaken research that has led to the development of the Bureau’s operational quantitative radar rainfall estimation and short-term rainfall forecasting system.

R Trevithick

Rebecca Trevithick is currently employed by Queensland’s Department of Natural Resources and Water, and is also undertaking a PhD at Griffith University. Her primary research interests are in the area of the use of GIS and remote sensing as enabling technology for environmental modelling purposes. Rebecca has been involved in a number of projects utilising GIS and remote sensing techniques in the development of input layers and parameters for various environmental models, including the SIBERIA and SedNet.

K Morris

Ken Morris is a principal engineer with Brisbane City Council. He has over 20 years experience at a senior in-line management level, providing direction and advice for the development of Brisbane’s waterways and floodplains, flood disaster management systems and environmental management projects. Since 2001, Ken has been tackling flash flooding head-on developing FLOODWISE. This system provides operational and management information to the Council, and eventually the community, as a means to mitigate damages that result from this type of flood. Projects Ken has managed include flood mitigation schemes, floodplain modelling, flood studies and stormwater management. He has developed a Waterway Information System and is the director of Brisbane City Council’s Flood Information Centre.