Monday, 5 April 2021

“The story of a little town in the Clarence Valley and a growing problem” - Part Two

 

On North Coast Voices blog on 1 April 2021 I placed a post titled “The story of a little town in the Clarence Valley and a growing problem”


The problem is flood risk – in a coastal town surrounded by ocean, river, channels and lake, with only one access road leading out to the wider Clarence Valley – and a growing population which may need to evacuate in times of major to extreme flooding.


When it comes to where water first appears within Yamba town limits this second post is a little more specific than the first.


I want to introduce what might be called the canaries in the coal mine when it comes to local flood waters. Yamba Road and the six streets listed below are fairly early indicators of what may possibly follow once the full flood front reaches the town.


These canaries are important, because during times when flooding occurs at the same time as ocean storms and surges, the volume of water entering Yamba is coming from both the Clarence River and the sea. Which means people in Yamba may only have as little as 6 to 12 hours notice of what is heading their way.


During flood events to date the only access road in and out of the town, Yamba Road, can have water either lying across the road surface or it can be cut by flood water sometimes long before the flood front reaches the town - at Oyster Channel, in the vicinity of Palmers Channel, at the Maclean-Pacific Highway interchange and later at Maclean town limits.


That part of Yamba Road within town limits - when it becomes a mixed commercial and residential street can have water across the road (sometimes at depth) at the intersection with Carrs Drive, in the vicinity of Lake Kolora and at the intersection with Angourie Road.


During these flood events water can also be found lying across other residential streets (again sometimes at depth) - such as Shores Drive, Golding Street, Telopea Avenue, Angourie Road, Carrs Drive and Sullivans Road. This is not an exhaustive list of streets where water pools or runs during flood events.


According to Clarence Valley Council’s own flood mapping extreme flood height predictions for these named roads and the houses that line them are:


Yamba Road – a height of 3.68-3.8 metres;

Shores Drivea height of 3.21-3.33 metres;

Golding Streeta height of 3.68-3.8 metres;

Telopea Ave – a height of 3.56-3.58 metres;

Angourie Road – a height of 3.33-3.8 metres;

Carrs Drive– a height of 3.68-3.8 metres; and

Sullivans Road– a height of 3.68-3.8 metres.


The majority of houses in the town are single story. These listed floodwater heights are well above the average ceiling height of a single storey house which is est. 2.74 metres. In fact, part of the roof of such a house would be submerged at that water depth.


Ironically, Yamba Bowling and Recreational Club which is the town’s designated evacuation centre – at which Yamba residents are advised to assemble, register & then self-evacuate to accommodation with family or friends on higher/dry ground – will itself have floodwater threatening to enter the building during an extreme flood event.


The number of dwellings estimated to be at risk of some degree of inundation in Yamba is 0 in a 1-in-5 year flood, 122 in a 1-20 year flood, 1,223 during a 1-in-100 year flood and 2,144 in an extreme flood.


The fact of the matter is that even in a 1-in-20 year flood Yamba Road will be cut at multiple points on its route through the town at predicted levels from 1.66-1.77m to 1.97-2.08m, which will see quite a few local residents with floodwater running through their homes from either about shoulder height of an average adult female or up to and over to the full height of a tall adult male.


That same flood event would likely see some residents in Shores Drive and Golding Street with floodwaters over the heads of both male and female adults in the household. Some adults at the vicinity of the Angourie Road turn-off will have at least chest-high water in the house. While Carrs Drive will be blocked by 1.35-1.66m of water and some Sullivans Road properties will be inundated to a height of 1.35-1.46m.


In three of the flood scenarios mapped for Yamba – commencing with the 1-in-20 year flood – the town is looking at between 3%-28% of all housing at risk of part or complete inundation in major flooding along the Clarence River and, up to 49% of all the current housing in the town at risk of total inundation in an extreme flood.


In 2008 when the flood frequency table cited was drawn up that last percentage represented the homes of est. 5,360 men, women and children.


As a significant portion of the remaining natural flood storage areas just outside of and within Yamba town limits continues to be drained, filled and covered with houses over the next 25 years or so; where flood waters enter the town, how fast these flood waters move and how much area they cover is likely to change from what has been seen in historical floods since the 1830s.


From this resident's perspective it's time all three tiers of government walked the walk as well as talked the talk when it comes to creating or maintaining sustainable populations on floodplains and in coastal zones in the face of ongoing climate change.


So I ask NSW Premier Gladys Berejiklian, Deputy-Premier & Minister for Regional New South Wales John Barilaro, Minister for Police and Emergency Services David Elliott, members of the Northern Regional Planning Panel and Clarence Valley Council – when are you all going to recognise that Yamba cannot keep growing its population without escalating risks to life and property during future floods and other natural disasters?


When as a way of curbing population growth on this section of the Clarence Valley floodplain are you going to place realistic, in the public interest, restrictions on housing density per hectare in both Yamba and the West Yamba Urban Release Area?


Of NSW Nationals MLA for Clarence Chris Gulaptis I also ask those questions – given that as a former surveyor, development application consultant, land developer and shire councillor he significantly contributed to three decades of urban development on the Lower Clarence section of the floodplain.


In addition I ask the Berejiklian Government, Clarence Valley Council and NSW State Emergency Services when are you finally going to address the fact that there is no viable evacuation plan for Yamba residents during major to extreme flooding events?


I’m sure those families with children and the estimated 37 per cent of the Yamba population 65 years of age and older would be most interested in your answers.



PRINCIPLE SOURCES:


Clarence Valley Council documents including flood mapping at

https://maps.clarence.nsw.gov.au/intramaps97/


Yamba Community Profile at https://profile.id.com.au/clarence-valley/about?WebID=240


2016 Census Quick State - Yamba (NSW) at 

https://quickstats.censusdata.abs.gov.au/census_services/getproduct/census/2016/quickstat/SSC14458#:~:text=In%20the%202016%20Census%2C%20there,up%204.5%25%20of%20the%20population.&text=The%20median%20age%20of%20people,State%20Suburbs)%20was%2056%20years


Images of Yamba during the 2009 flood



TOP: The Daily Examiner photograph of Yamba from the air showing a section of Crystal Waters, Oyster Cove and West Yamba.
MIDDLE: Fletchers Fotographics' Dave Brandon photograph of flooding during the night.
BOTTOM: Vicki James blog had this shot of Shores Drive, Yamba.


Image of a section of Yamba Road during March 2021 flood

The Daily Telegraph, 24 March 2021


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