The Lismore City Council’s Flood Risk Management Committee is to consider asking the CSIRO to review and update its Flood Risk Management Plan, at a committee meeting this week.
Independent Councillor Big Rob is a committee member and has raised the motion recommending the council consider submitting the request along with a cost estimate for the work.
Agenda notes suggest the council would ask the CSIRO to start the review once the science agency’s work on a Northern Rivers Resilience Initiative (NRRI) flood modelling project finished.
Executive summary notes on the agenda item say the review would mean the council’s Flood Risk Management Plan would ‘move away from design events, and model flood events on up to date actual flood data’.
Design v actual event data pros and cons
The council’s senior strategic planner provided information for the agenda item, including some listed advantages and points for consideration.
Advantages reportedly include updated information that reflects regional flood characteristics and impacts more accurately, the ability to reference known events and the possibility of identifying ‘risks not captured by standard design events, especially in areas with complex
hydrology or recent changes in land use or climate’.
Considerations listed include the possibility of historical data being ‘limited in scope, quality, or consistency, especially for older or less documented events’, while actual events represent specific conditions and ‘may not account for future variability or extremes’.
Using actual events alone, the notes say, may not provide ‘the full range of scenarios needed for comprehensive planning’.
This, staff note, is why design events remain a standard practice.
Advice from the Australian Institute for Disaster Resilience (AIDR) Guidance, meanwhile, is to have ‘a risk-based approach that integrates both design flood events and actual flood events’.
Triggered much: official suggestions for when to review a flood risk plan
The government’s NSW Flood Risk Management Manual recommends Flood Risk Management Plans be reviewed at least every five years, after a major flood or after updates to flood modelling data and that the documents be considered ‘living documents’.
‘Social, economic and political circumstances can change,’ the manual reads, ‘as can catchment and floodplain conditions, knowledge of flood behaviour, or the effectiveness of existing FRM measures’.
‘Where necessary, a plan should be revised to address any key changes or deficiencies in the recommended measures,’ the manual reads, before describing a range of circumstances that may trigger the need for a review.
When ‘the needs of the community change significantly,’ or when ‘a significant flood occurs that has behaviour or impacts that are not consistent with the existing understanding of flood behaviour,’ are two listed triggers for a review.
Other triggers include the proposal of ‘significant changes in the strategic approach to land use or future land-use trends in the floodplain or catchment’.
The manual also says new technologies ‘may change the utility of different management measures or provide the basis for new management measures’.
It says any review of an FRM plan should account for changes across the full range of issues originally addressed in the plan, consider any emergent issues and, where relevant, inform broader management reviews.
When to call in state agencies for a review
A review may be considered simple or more detailed, with a simple review generally undertaken with a council’s resources.
‘Depending on the scope and scale of the review, input may be sought from relevant state agencies and potentially an FRM committee,’ the manual states.
‘A more detailed review may be triggered where: the simple review identifies that the original direction in the plan needs reconsideration; new flood information or guidance is available that may influence FRM priorities and directions; or the effectiveness of implemented or proposed FRM measures needs to be reviewed,’ the manual says.
External resources and more input from state agencies, an FRM committee and the community may be required for a detailed review.
The manuals says reviews should lead to ‘broader review of all relevant activities under the FRM framework’.
‘This may include updating flood information, changes to FRM status, priorities and forward plans including IP&R framework activities, FRM arrangements, DCPs and EM planning.’
The Lismore City Council Flood Risk Management Committee is due to meet on Wednesday 3 September from 1pm in the council chambers at Goonellabah.
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