Merri gets muddy – twice!
Merri Creek has dramatically changed colour twice; firstly after heavy rain in mid-May and then again in mid-June, just as it was starting to clear up a bit. The change, from its usual darkish hue to a worrying, pale-yellow was much worse than anything we’ve seen before. Both Melbourne Water and MCMC investigated, and the MCMC Manager, Luisa Macmillan, traced the pale yellow colour to Kalkallo Creek which joins the Merri near Donnybrook.
Rural parts of Kalkallo Creek have erosion gullies metres deep and most of the sub-soils across the catchment are highly erodible and sodic (sodium-containing). They rapidly lose their structural integrity when wetted. Unfortunately, these soils underlie new residential and employment areas being developed west of the Hume Highway, north and south of Donnybrook Rd. The major source of the problem is that these soils are exposed during construction and if there are any sediment controls in place, they are failing abysmally. See more here.