Location of Tocal
Tocal is located in the lower Paterson Valley of the New South Wales Hunter Valley. The Hunter River is the state's largest single coastal river system, covering an area of 22,000 square kilometres. The Hunter River system passes through the Great Dividing Range in one of the few east-west breaks in the range. This break marks the geological border in the Great Dividing Range between the Carboniferous mountains to the north and the Sydney sandstone basin of the Permian era to the south.
The Paterson River is one of several tributaries to the Hunter (others include the Allyn, Williams, and Goulburn Rivers). Each of these rivers flows from the Barrington Tops (on the southern end of the Carboniferous mountains) into the Hunter River. The valley floor contains relatively recent (around 6,000 years old) alluvium from the Quaternary era.
Tocal is mostly contained in the Webbers Creek subcatchment, Webbers Creek being a tributary of the Paterson River. Tocal almost spans the Webbers Creek catchment and interestingly contains the northern tip of the Sydney sandstone basin in View and Bush paddocks (see more about the soils of these paddocks), the Carboniferous mountains on the northern side of the Webbers Creek valley and the Quaternary alluvium of the valley floor (the Top Flat soil profile is an example of the older Quaternary alluvium, while Windmill paddock is an example of the newer lighter alluvium). This mixed geology creates a range of soils on Tocal.
The rim of the Webbers Creek valley rises about 300m above sea level (the peaks of Tocal are around 200m). This rise is the first encountered by maritime air masses moving west from the coast, often creating violent thunderstorms within the Webbers Creek catchment. The Webbers Creek catchment has a noticeably higher rainfall than the areas to the north, south and west. This, combined with the long narrow Paterson catchment and the tidal nature of the Paterson River below Tocal, means that Tocal experiences regular flooding in areas below 10 metres.
Map of Australia showing the location of the Hunter Cathcment