Flooding and the Coffs Harbour Regional Airport – A report gives conflicting outcomes

With the long term lease for the airport to be signed soon in February we thought it might be time to revisit it and look at some issues in relation to it.

By The Editor

Today in Part 1 we look at the issue of flooding associated with natural coastal processes and hazards and coastal management control.

A number of Councillors apparently opposed what is essentially the privatisation of the airport because they intimated they did not think the price was right among other issues.

As outlined here  the agreement includes $81.5 million in fixed payments over an initial period including for the development of the Airport Enterprise Park, a 23-hectare greenfield employment precinct adjacent to the airport.

Council will also receive a share of revenue earned from both the Airport and Enterprise Park, forecast by Council to be in excess of $400 million over the term of the lease and option. Palisade will be able to take up the 49-year lease extension option after 50 years subject to a range of legal and commercial requirements being met.

However, there is a feeling that the current Covid affected aviation situation meant a buyers market existed and a better price could have been obtained in about five years time.

Nevertheless, other factors could have been at play in the final offer made by Pallisade Investments to the CHCC.

One key factor Pallisade may have taken into account as part of their due diligence could be possible flooding.

A March 2020 report done by consultants BMT WBM titled ‘Coffs Harbour Coastal Zone Management Plan’ (CZMP) outlines numerous issues Council will need to take account of given predicted rising sea levels and increased rain depressions which can cause increased flooding.

The updated 2019 CZMP for the Airport is reproduced from the report below.

As can be seen it shows what seems to be a reasonably manageable flood risk if one follows the colour key in the top left corner.

However, later on in the 143 page report the following asset risk register appears on pages 124-125.

As can be seen here there is a far less benign outlook in regards to the airport and any flood risk associated with it.  Suddenly the risk is ‘extreme’ and is ongoing for the next 100 years. 

Remediation work is listed as ‘immediate.’

It is important to highlight here that this refers to the airport as a whole.  This means the runway, terminals and all air-side facilities too. 

So any remediation being done land-side to the proposed Enterprise Park does not covere this.

Having flooded extensively in 2009 BMT are here telling Council that the airport is still a high flood risk, if not even worse.

And, along with the Pacific Highway, areas around Coffs Harbour North, Hogbin Drive, Sawtell Road and the nearby railway line are all subject to extreme flood risk now and that remediation should be done now.

As a result the question rises as to why two seemingly conflicting outcomes in relation to the airport appear in the report.

One ‘school of thought’ is that the asset risk register appears on pages 124-125 was done earlier, possibly around 2012 and was mistakenly left in the 2019 report. 

Others are of a view it was left deliberately in so as to highlight ‘the real picture’ in regard to the airport and surrounding areas.

Might it not be possible that as part of their due diligence Pallisade came to the view the asset risk register that appears on pages 124-125 of the CZMP report is correct and adjusted their offer accordingly?

3 thoughts on “Flooding and the Coffs Harbour Regional Airport – A report gives conflicting outcomes

  1. A great piece of investigative journalism Ed.

    The rain that fell upon the Coffs Harbour area during March and November 2009 created serious and flood conditions. Records show that 405mm of rain fell within a one 24-hour period.

    With so much building of commercial premises forecast to be built at the 23ha Enterprise Park site, the effect of rooftops, increased hard surfaces such as concrete pathways and new roads, will seriously impact on where rain water will drain and flow to. Remaining exposed lands will become more swamped, surface water levels will rise and streamflow will increase. According to Flood Specialists, flood modelling makes this abundantly clear

    The question is:- Is Coffs Harbour City Council willing to guarantee Palisade there will no recurrence of the conditions that prevailed in March and November 2009, within the next 100 years, within the next 50 years or within the next 5 years? Is this perhaps why Palisade “got it cheap”??

    Consider the following:-

    A one-hundred-year flood is a flood event that has a 1% probability of occurring in any given year. The 100-year flood is also referred to as the 1% flood, since its annual exceedance probability is 1%

    The term “100-year flood” is used in an attempt to simplify the definition of a flood that statistically has a 1-percent chance of occurring in any given year. Likewise, the term “100-year storm” is used to define a rainfall event that statistically has this same 1-percent chance of occurring

    Recurrence intervals for the annual peak stream flow at a given location change if there are significant changes in the flow patterns at that location, possibly caused by an impoundment or diversion of flow. The effects of “development” on peak flows, is generally much greater for low-recurrence interval floods than for high-recurrence interval floods. During larger floods, the soil is saturated and does not have the capacity to absorb additional rainfall. Under these conditions, all of the rain that falls, whether on paved surfaces or on saturated soil, runs off and becomes stream flow.

    Think about it readers and you Councillors !

    1. All well and good Neptune but what about the effect of king tides and full moon flood tides coinciding with your one in one hundred year event which can now occur at random according to Science ?
      Are we nearing a tipping point for extreme weather? That is floods and drought. No doubt about it and what’s worrying for Coffs Harbour and the airport, is that we have a City Council with a few Councillors and an executive management blinded by the dazzle of near term dollars.
      At some point Palisade will come down heavily on CHCC when their revenue is impacted by events that can’t be claimed under force majeure.
      “Oh sorry, didn’t we tell you it sometimes rains in Coffs Harbour” says the GM.

      1. Any future flooding events will be insignificant compared to the king tide that will sweep councillors out of office for betraying future generations for short term gains.

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