Who killed Cockle Creek?

OK, I don't think it's quite dead. But it's looking a bit poorly.

Yesterday my bushwalking club did a nice little Ku-ring-gai Chase National Park walk - from North Turramurra down to Bobbin Head and back, coming up via the Gibberagong and Murrua tracks. We were very struck by the badly polluted state of Cockle Creek, especially in the region of the Gibberagong Waterholes. It looked like a big overflow of sediment from some development project upstream.
So today my mission was to track down the culprit.



A couple of kilometres upstream, Cockle Creek runs alongside the M1 Pacific Motorway, and the NorthConnex tunnelling project. A prime candidate for pollution suspicion. So I headed off into the bush on an intrepid journey of discovery out of Asquith, through a proudly graffitied tunnel under the motorway, and down a long, steep, slippery (and unpolluted) creek bed.

















When I arrived at Cockle Creek it was also clean. NorthConnex was off the hook.






Back on the job, I drove to North Wahroonga, and headed off  along the fire trail towards North Turramurra and Bobbin Head Rd. I checked each of the tributary creeks, and every one of them was clean.



Until the last one.  Lovers Jump Creek was cloudy grey and clearly sediment-polluted.

The water dragon didn't seem too put out by it, but there again, he was staying out of the water!


There was a rather ineffectual looking yellow plastic sheet across the creek (a 'water-gate'), implying that the powers-that-be were onto the case. The water gate didn't actually seem to be doing much though.

So where was the source of the problem?

I headed further upstream. And I think I found it. In Karuah Rd, Turramurra, alongside Memorial Park, there had been a landslide/roadworks/failed roadworks episode. The dirt had fallen into the creek. Below that point it was polluted. Upstream it was clean.

More fire trails

This time I explored the fire trails that circumnavigate the suburb of Cherrybrook. In particular, the Kentia Trail, the Carmen Trail, and the Daphne Trail. There are, as ever, some quite scenic sights to behold.

There are colourful cliff faces, and sunlit vistas across valleys.

There are a couple of recent man-made additions: bioretention filters, which capture pollution from stormwater run-off, using sand and appropriate plants.

And speaking of man-made additions, the fire trails themselves are here to protect the houses above from bushfires, by acting as a barrier, and by providing access for firefighters to fight fires, and to start them (as in hazard reduction burning). The Daphne Trail was used for a burn a few weeks ago.

There's a kind of beauty in the stark imagery and colours after a bushfire. And the bush does grow back, but the weeds tend to grow first, and the ecology is probably not really adapted to fires coming as frequently as they do these days.