Weather we could improve our warnings
IN THE days ahead of the flooding caused by ex-Tropical Cyclone Debbie the Bureau of Meteorology issued a series of watches and warnings from their NSW Operations Centre for the Northern NSW community.
The first notification, 'Flood Watch For the Northern Rivers and Upper Macintyre Valley', was released on Tuesday March 28 at 2.28pm. It said quite clearly that the weather system had the potential to cause river flooding and local flash flooding along the Tweed, Brunswick, Richmond-Wilsons, Clarence and Upper Macintyre Valleys.
The Richmond-Wilsons was listed having the potential for 'moderate to major' flooding.
The bulletin was re-released by the Richmond Tweed Region SES: 'Flood Watch for moderate to major flooding on the Tweed, Brunswick, Richmond & Wilson Valleys issued by the Bureau of Meteorology”.
No specific towns were mentioned in either alert as they focus solely on river systems and it's not clear who saw them.
The BoM's 'National Arrangements for Flood Forecasting and Warning', last reviewed in 2015, states: "There is no specific responsibility on agencies with a role in water data collection to establish special purpose flood warning networks.”
"Despite this however, strong cooperative relationships have been developed among the agencies concerned and the Bureau of Meteorology and arrangements to provide data to the Bureau have developed on an informal cooperative basis, with different arrangements applying in each jurisdiction.”
The document also says that the state or territory Government's role includes "providing a component of the real-time data collection network used for flood prediction.”
Questions could be asked about whether or not the data collection network is actually real-time.
Region controller for the SES Richmond Tweed, Mark Somers, said the data they had access to is real time, while the Lismore Citizen's Review cites a time lag of several hours at times between the river gauge heights the BoM was reporting online and what was happening on the ground throughout the catchment, during that critical time frame on Thursday morning.
The BoM did not respond to this question at the time of printing but they do need to verify river gauge readings before disseminating them (just in case someone pees in the gauge, for example).
Local rain gauges are currently the responsibility of four different agencies, the Office of Environment and Heritage, the BoM, NSW Office of Water and Local Councils. Their repair is contracted to MHL who will, it has been said, go out in the middle of a storm to fix them if required.
In a statement from the BoM, NSW State Manager Ann Farrell said of last year's flood: "As with all severe weather events, the Bureau operated 24 hours a day and drew on surge support from its other offices around the country to help with forecasting as rainfall and flooding developed.” The Northern Star understands the office options in this scenario are Sydney or Melbourne.
"Forecasters drew on information from the 16 rainfall gauges in the catchment upstream of Lismore, and two rainfall gauges in Lismore. These gauges report automatically, with the hourly rainfall amounts available on the Bureau's website.”
At least one faulty gauge was reported during the event and not noted on the flood warnings. This process has been changed for future events.
"The Bureau issued a watch for moderate to major flooding at Lismore on the Tuesday afternoon, more than two days ahead of the levee overtopping,” said Ms Farrell.
"The Bureau then issued severe weather warnings for heavy rainfall on Wednesday morning.
"At 3.38pm on Thursday, 30 March 2017, the Bureau issued a major flood warning for the Wilsons River. It warned that flood levels at Lismore would reach 11 metres early on Friday morning.”
Since the flooding, the Bureau has attended several post-event reviews and meetings in the Lismore region, including community meetings led by the SES and a meeting with community members hosted by Mr Kevin Hogan, MP for Page.
"The key lesson we have learned is that we need to continue to work with the SES, the media and the community to enhance how weather and flood warnings are communicated to those who need them,” said Ms Farrell.
"We have already put a number of changes into place to better serve the Lismore community.
"Future flood warnings in the area will now highlight predictions exceeding 10.6 m, which is the approximate height of the levee overtopping. Guidance used by our forecasters now includes an empirical flood forecasting method shared by a local community member. We are also working closely with local SES on new and improved processes for sharing local intelligence during flooding.”
The flood levee overtopping could, according to the SES, start anywhere between 10.2 and 10.6m.
On January 31 Kevin Hogan, Thomas George and the Lismore Citizens' Flood Review Group met with the BoM's National Director of the Dr Andrew Johnson, NSW Regional Director and the Senior Hydrologist of the Climate and Water Division.
Dr Johnson and his team were presented with six recommendations.
These include developing a process that enables current local rainfall and creek heights from identified local contacts to be reported directly to the BoM, establishing a fully integrated information and communication system that includes this local intelligence and is visible on the Bureau Web Site, and using this system as part of a common system where information is shared with all emergency agencies. The recommendations also include the addition of two new flood warnings, an Initial Flood Warning which would sit after the Flood Watch to warn of the probability of a flood, and a Final Flood Warning.
The last two recommendation include the need for hourly updates during an event and the addition of probable consequences to the warnings and an overtopping time.
"Assurances have been given that the recommendations will be seriously considered as it is evident that their application could have benefits nationally,” said the co-ordinator of the Lismore Citizens Review group, Beth Trevan.