River bed mapping to help flood forecasting

A team of CRC researchers has been measuring the shape and depth of the Clarence River bed in northern New South Wales as part of moves to improve flood forecasting for the area.

Lead by Project Leader Associate Professor Valentjin Pauwels (Monash University), the team used a HydroSurveyor, which includes an echo sounder, a Doppler velocity profiler and GPS antenna, to help build a three-dimensional map of the river bed.

The new mapping will cover an area from Mountainview (about 18km upstream of Grafton) to about Copmanhurst (about 20km further upstream) and will be added to existing three dimensional maps of the river bed from just upstream of Grafton to the river mouth.

It will be used to help calculate the capacity of the river to deal with incoming flows.

A/Prof Pauwels said the flood forecasting work, a key component of the ‘Improving flood forecast skill using remote sensing data’ project, was based on two models: hydrological and hydraulic. The hydrologic model used rain forecasts to compute the amount of water entering the system and the hydraulic model computed how water entering the system travelled downstream.

“With that information we can predict water depth and velocity at any point in the valley,” he said.

“Our team is convinced the use of satellite and airborne remote sensing data to correct numerical models in real time will improve the accuracy of the flood forecasting system.”

Associate Professor Pauwels, who was supported in the research by fellow CRC researchers Professor Jeffrey Walker, Dr Yuan Li, Dr Stefania Grimaldi and Ashley Wright, said the Clarence River was affected by major floods in May 2009, January 2011, January 2012, January 2013 and February 2013.

“An improved flood forecasting system will enhance the emergency management capability, thus reducing the flood-related financial costs and community discomfort,” he said.

“The availability of timely and accurate flood forecasts will allow for time-effective warnings, the implementation of evacuation plans and the set-up of safe recovery and storage areas.

“Floods are the most common and deadliest natural disasters in Australia. Between 1967 and 2005 the average direct cost of floods in Australia has been estimated at $377 million.

“We hope this research will produce more accurate flood height predictions.”

Clarence Valley Council  local emergency management officer, Kieran McAndrew, said the Clarence River was the heart of the council area. 

"It is the largest of all NSW coastal rivers in catchment area and river discharge, which means flooding is part of life for the community of around 50,000 people," he said.

"Clarence Valley Council is happy to support and help research projects where it can, but especially when the outcomes of such research have the potential to improve flood peak estimates and flood warnings. 

"The Clarence Valley community relies on warnings to prepare for imminent flooding, so there is a real benefit to be gained from the research. 

"Because council believes in the benefits of the CRC project it has been collaborating with researchers and helping them find data for their project," Mr McAndrew said.