Some building certifiers have interpreted conditions requiring raised floor levels as permission to use fill on flood-prone land, even though the filling required specific assessment, a Byron Shire Council report reveals.
Photo Jeff ‘Big Digger’ Dawson.
The report acknowledges that the interpretation was not consistent with development approvals, raising questions about how earthworks were authorised and their potential effects on surrounding properties.
Prepared for council’s Floodplain Risk Management Advisory Committee today (Thursday, October 29), it also discloses that council has changed its approach to a standard condition covering retaining walls and earthworks.
‘Council no longer applies its standard retaining wall and earthworks condition to all developments,’ the report states.
Those conditions are now imposed only where earthworks form part of the approved proposal.
The report responds to an issue raised at the committee’s August meeting: buildings being approved with conditions requiring raised floors without recognising the impacts of fill used to achieve those levels.
It explains that some certifiers historically read minimum habitable floor-height requirements, together with council’s standard earthworks condition, as authorising filling.
Staff describe that interpretation as ‘not necessarily consistent with the development approval’.
Raising a building’s floor and raising the surrounding ground involve different flood considerations.
Council’s planning controls recognise that fill can affect flooding beyond a development site and obstruct existing overland flow paths unless suitable alternative drainage is provided.
Filling may also be unsuitable because of a location’s flood hazard or function, or the cumulative impacts of development across an area.
Where filling is proposed, staff say it must be assessed against council’s Local Environmental Plan and Development Control Plan. Depending on the circumstances, applicants must provide a flood impact and risk assessment, and detailed modelling may be required.
However, the report does not identify affected developments, quantify how much fill was involved or establish that neighbouring properties suffered additional flooding.
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