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| The road into Yamba, Clarence Valley NSW, 4 March 2022 Credit: Clarence Valley Council via Storyful in Yahoo! |
To put it frankly Yamba township’s flood resilience is a shambles.
Surrounded on all compass points by river, lake or ocean, much of the urban footprint of the town is built on degraded sand hills and reclaimed marshland or swamp across 16.92 sq km of coastal land.
The natural fingers of the Clarence River estuary which intrude into residential streets are now exacerbated by a fringe of canal estates which bring tidal riverwater right up to the artificial soft shore boundary edges of the backyards, side yards or front yards of so many homes and make it possible for riverine flooding to enter more streets than it once did.
Ocean storm surges occurring during destructive East Coast Low storm events are something that are considered almost in passing when it comes to resilience planning and flood risk management. Even though authorities are aware that days of heavy rainfall leading to soil saturation accompanied by strong seas result in est. 1 in 1,000 chance that land slippage will affect sections of Yamba Hill & environs public and private property – including residential dwellings. Such an event can coincide with riverine and stormwater flooding in wider Yamba.
The Lower Clarence River floodplain spans 500km2. That is a substantial floodplain and climate change modelling in BMT Lower Clarence Flood Model Update 2013 indicates that all along the lower river peak flood levels are expected to increase in 1% AEP events.
The natural protection of Yamba’s 690ha natural flood storage area has over time been eaten away by extensive landfill earthworks being created in preparation for housing another 2,000-2,500 people in West Yamba. While completed large scale earthworks elsewhere in Yamba are contributing to increased stormwater flooding adding to the volume of flood water flowing in from the Clarence River and into internal waterways and floodways of a town whose current population is 6,388 men women and children living in a density of 377.6 persons per sq km.
Coping with the town’s street plan and road surface heights which lead to predictable internal road closures during major flooding. These closures will inevitably occur ahead of any official advice to immediately evacuate during a Lower Clarence River flood. Currently it appears such emergency advice is not planned to be given until flood height reaches 2.1m at Maclean – at which point Yamba’s only evacuation route is highly likely to be closed in both directions.
In 2022 any evacuation by vehicle ahead of a flood front was calculated to take a minimum of one hour for the journey to Maclean via Yamba Road and the Pacific Highway to be completed. A journey that in good conditions might take twenty minutes. [C. Landers, Clarence Valley Council correspondence, dated 30 June 2022]
When it comes to Yamba residents and visitors; state & local government along with emergence services have placed the primary emphasis on “self-help" when coping with rising floodwaters or a need to evacuate, due to limited SES resources being spread across the valley.
Added to this is the fact that Yamba's flood heights expected ahead of active flood fronts and actual flood front heights as they reach the town are broad estimations. Because the town has to rely on the Maclean flood gauge further inland due to the strong tidal movement at the river mouth which is said to distort any flood calculations derived from the Yamba tidal gauge situated in the vicinity of the start of the southern breakwater wall.
Yamba is an accident waiting to happen and, it does not inspire confidence, when reading between the lines of the following newspaper article it seems that Clarence Valley Council administration is reluctant to obtain a written record of the lived experience of the wider population in Yamba over the last three decades. Something that would complement the data contained in the anticipated report by BMT WBM Pty Ltd.
Clarence Valley Independent, 17 May 2023:
The Yamba Community Action Network Yamba CAN Inc is urging Clarence Valley Council to conduct a flood survey of all residents on the Yamba floodplain so it can be incorporated in the updated Clarence River Flood Study and Flood Model which are currently being prepared.
Consideration of the impacts of the devastating floods in February and March 2022 will be factored into council’s new Flood Study and Flood Model, and Yamba CAN Inc believes the studies would be better informed if a survey was done to understand the impacts on individual residences.
When Yamba CAN recently discovered a flood study being conducted by Coffs Harbour City Council of residents in the Moonee Creek catchment area, members questioned why CVC couldn’t do the same.
Flooding impacts areas of Yamba differently, so to get a comprehensive picture of how the entire Yamba floodplain is affected, Yamba CAN Inc suggests CVC adopt a similar model to Coffs Harbour City Council, by asking each household to describe how they were impacted.
Questions in the Moonee Creek flood survey include: how long have you lived in the region; have you experienced flooding within the Moonee Creek catchment; have you experienced any other flooding event; please provide a short description of any flooding you have experienced; whether your home/business, garage, yard was flooded; were you able to drive your vehicle to safety; what areas of the community are most at risk of flooding; have you noticed any changes in the frequency or severity of flooding in your area and to provide photos and depths of the flooding.
From answers to these questions, Yamba CAN Inc asserts CVC could develop a comprehensive flood model of how individual residences are impacted in times of flood.
The important information obtained from the survey would assist with any upgrading of west Yamba’s stormwater drainage system.
Yamba CAN Inc sent a letter to CVC General Manager Laura Black, and all Clarence Valley Councillors calling for a flood survey of residents living on the Yamba floodplain to be included in the updated Flood Study and Flood Model.
“It has come to Yamba CAN Inc’s attention of another flood study being undertaken by Coffs Harbour City Council in the Moonee Creek Catchment area,” the letter states.
“This flood study includes gathering information from all residents in the Catchment area by means of a survey.
“A similar survey of residents living on the Yamba floodplain is of paramount importance to be included in the current Flood Study and Model, particularly not only in relation to riverine flooding but stormwater flooding during February/March 2022 which occurred two days prior to the Clarence River flood crest reaching Yamba.
“Yamba CAN Inc requests CVC undertake such a survey and the results be considered in the formulation of the current Flood Study and Model.”
A Clarence Valley Council spokesperson said council engaged BMT to undertake flood modelling using the latest available property and event data for the local government area to inform Floodplain Risk Management Plans.
“The plan will be presented to the Council for exhibition, providing opportunity for the community to comment and provide feedback,” the spokesperson said.
The spokesperson said council doesn’t plan to do a survey of impacted residents in Yamba.
“Council does not intend to survey individual households in relation to this matter,” the spokesperson said.
“However, we will be undertaking a Yamba Urban Drainage Survey to capture residents experiences in recent events, as we are currently doing for Iluka.”
