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Reducing flood risk in Lismore starts with better data

  • 19 July 2022
Flooding has affected much of eastern Australia this year, and Lismore NSW has been amongst the worst affected areas. How is it that Lismore, one of the most flood-prone towns in Australia, can be so ill-prepared and so badly affected by floods this year? What can Lismore do to reduce its flood risk, and what are the implications for others? These are important questions, especially now as the newly constituted Northern Rivers Reconstruction Corporation assists flooded towns in the region to make pivotal decisions, hopefully on the basis of reliable information. Flood frequency is critical information, so you might expect that such guidance was based on the best available data – but this does not appear to be so.

Lismore has a long history of forgotten floods, so serves as an interesting case study of selective memory when it comes to flood risk. Despite this lapse, it seems that Lismore is not wilfully negligent, as a partial flood history 1870-1922 is freely available on the Council website (a different more detailed version here), and the 1974 flood height was prominently displayed on many power poles throughout the floodplain. How did ’74 become the yardstick? And why is it that we all too often hear that ‘I did my due diligence … when the water raced in … my dream turned into a death trap’?

Forgotten floods of Lismore

Estimates of early floods in Lismore rely on newspaper reports of the day, because formal streamflow monitoring first commenced in 1943, decades after the town was declared in 1856. Floods were reported almost immediately. In 1857 flooding was widespread on the east coast, including the Richmond River which had

‘dreadful floods … grievous loss’, but there is no record of river heights. In 1859 it was reported that ‘floods have brought out a good deal of fine cedar’. The 1861 flood was ‘the highest and most disastrous flood’ with water 29 inches deep in the blacksmith shop,‘the floor of which is level with the street’. This smithy was at the intersection of Molesworth and Woodlark Streets in the present CBD, just below 11m AHD, so we can surmise that this flood reached 11.7m in this eastern branch of the river. But we also read that ‘the palisading and fencing around the cemetery was torn away’ by the current. The North Lismore cemetery ranges from 12-24m AHD, so the water level must have been over 12m in the