Flooding

The Peterhead floods of 14 Feb 2014 focussed atention on the storm water provisions of the development plan - mainly that development "should" not occur unless the public stormwater system could cope with a 1 in 100 year storm. The 14 Feb storm was estimated to be a 1 in 20 year event and it was obvious that the system could not cope.

The Port Adelaide Enfield Council resisted requests for stormwater information, and eventually were forced to do so by the court. The reasons soon became obvious.

The Peterhead problems (and their solution) had first been identified in the 70's and further confirmed in the Lulu Tce reports of the mid '90s (see below). Council had not acted on the report's reccomendations, and indeed were not able to provide evidence of any action since.

Indeed it turns out Lulu Tce contained the main Peterhead drain to the Port River. At some time in the 90s council privatised Lulu Tce and sold it to Adelaide Brighton Cement to expand their cement works. The drain currently sits beneath the weight of the main Adelaide Brighton Cement stack and can no longer be maintained.

In what appeared to be a rather cosy arrangement, Council did not engage a stormwater wittnes, but On The Run engaged Council's storm water consultant Ken Schalk of Tonkin Consulting.

It seems that Tonkin hold Council's stormwater data or at least control access to Council's stormwater and tidal models. In any case the only data available to PAREPG's expert witness Dean Nobbs was that held by Tonkin.

On this basis the expert witnesses agreed that the On the Run site was one of the few Peterhead sites that was unlikely to be flooded 1 in 100 year storm. The point of disagreement was how much the runoff from the site would contribute to raided water levels in a major storm.

Tonkin held that it would be trivial under a new pumping regime designed by Tonkin. Dean Nobb's view was that the new pumping sytem was only capable of dealing with a 1 in 5 year storm - anything greater was likely to cause flooding - which was consistent with evidence supplied by residents of converations with Council.

The excerpt below of Dean Nobb's evidence from the court transcript probaly says it all:

Q: So just in conclusion, when the new storm water system is running at full capacity and we don't have a lot of clarity about when that full system is actually even going to be up and -

A That's correct

- operating at full capacity. But at the time which it is in place, so when it – as a 1:5 kind of system, is it true to say that the additional run off from this development once we get past a 1:5 flood, that additional flood water is going to basically into people's back yards, into their garages, under their floors, into their living areas, is that -

A That's correct

Evidence presented:
Expert witnesses joint statement
PAREPG: - Dean Nobb's expert witness statement
On The Run: - Ken Schalk's expert witness statement

Documentary evidence ordered by the court during the directions hearings:
Hargrave St Map 2
Hargrave Catchment Map 3
Hargrave St Proposed SW drainage
Lulu Tce drainage study 1997
Lulu Tce Drainage Study 1999
Flood scum line
Council notes