I am commenting on the environmental survey and stormwater modelling used for this site.
The biodiversity survey mentions that gang-gang cockatoos were not observed during the survey but are likely to occur within the site. I would like to state that I have observed gang-gangs in the site. The survey makes no mention of tawny frogmouths (Podargus strigoides), however I have observed these frequently near to the site.
The stormwater report did not include the actual modelling conducted (eg. Music msf files), so it is difficult to make an assessment of the modelling. Further, many of the reported results of the modelling did not even include units (eg. tables 6.4, 6.5). Let us hope that more attention to detail was put into the modelling than was put into the writing of the report.
All the planning and analysis of the site appears to rely on the official BMCC mapping of the watercourses of the site. However, immediately downstream of the site the stream no longer follows the mapped route but has moved a substantial distance to the West. In its current location the stream is deeply incised, with an unstable gully several metres deep undermining the end of Carlton St. This gully is continuing to progress up gradient by some combination of knickpoint retreat and pipe erosion collapse. I am not sure if the gully head has yet reached the site, however if it has not it will only be a few years before it does.
This raises two important issues. Firstly, the planned Eastern detention basin as well as the 0.2EY overflow line may both enhance the rate at which this gully head expands into the site. Over the medium term, the gully may well undermine the detention basin. Secondly, the environmental buffer zones based on the location of watercourses may not be correctly located if they are based on old council mapping rather than the current location of the channel.
In terms of the biodiversity offsets required for this development, restoration works on Kedumba Creek would appear to be more useful and appropriate than buying offsets in some far off place. As I suggested in a report prepared for council on the geomophology of the section of Kedumba Creek adjacent to this DA site, a series of leaky weirs will likely address the root cause of the gully erosion that is threatening to extend into the site. Specifically, a significant weir directly upstream of the culvert underneath Neale Street as well as several smaller weirs upstream will reduce the hydraulic gradient and promote sedimentation and aggradation. Additional water diversion measures will likely also be required upstream of the gully head.
Finally, I would like to make a general comment. A whole series of reports were prepared for this application. Several of them used abbreviations without defining the meanings of these abbreviations. While the meaning of these abbreviations may be obvious to practitioners within the field, the reports are not merely technical documents, but part of an important democratic process. Not defining terms makes these reports less accessible to the public who will ultimately be the ones effected by the development. I believe that council, on behalf of its citizenry, should make it clear to developers, and the contractors they engage, that this sort of anti-democratic behaviour will not be tolerated.
