parks victoria technical series marine natural values study vol 2 ...

Parks Victoria Technical Series No. 79
Flinders and Twofold Shelf Bioregions Marine Natural Values Study
Tidal variation is 0.9 metres for spring tides and 0.6 metres for neap tides (Plummer et al.
2003). Strong tidal currents (2 to 2.5 knots) are characteristic of this area (ECC 2000). The
area is protected from south-westerly swells by Tasmania but is strongly influenced by
south-easterly and easterly swells heights of 1.0 – 1.5 m, with maximum heights varying
between 1.9 and 2.7 m (LCC 1993). The combination of these tidal currents and high energy
swells result in well-mixed coastal waters (ECC 2000). Wave action is the main source of
beach erosion in the park (Parks Victoria 2006e). Wind patterns also influence
hydrodynamics, with south-westerly winds dominating in winter, resulting in an overall northeasterly
movement of water and sand along the coast (ECC 2000).
Three waterways and one saline waste water outfall discharge into the sea in the vicinity of
the park (Parks Victoria 2006e). Merriman Creek discharges intermittently into the sea
approximately 500 m north-east of the park, and the overflow from Lake Dennison, locally
known as ‘The Fisheries’, very occasionally discharges approximately three kilometres to the
south-west of the park boundary (Parks Victoria 2006e). Mason Creek runs directly into the
park (Table 10). The saline water outfall is associated with electricity production from the
Latrobe Valley and discharges 4 km south-west of the MNP at McGaurans Beach (Parks
Victoria 2006e).
Table 10. Physical attributes of the Ninety Mile Beach Marine National Park.
Park Name
Ninety Mile Beach
Conservation status
Marine National Park
Biophysical Region
Twofold Shelf
Size 2650 ha (ranked 9 th of 24)
Length of adjacent coastline ~ 5 km
Shoreline geology
Quartzose sands
Area with depth:
< 5 m 136 ha
5 - 10 m 168 ha
10 - 20 m 2085 ha
20 - 30 m 261 ha
Mean tidal variation - spring 0.9 m
Mean tidal variation - neap 0.6 m
Mean water temp - summer 18 o C
Mean water temp - winter 13 o C
Adjacent catchment
Agricultural, Urban
Discharges into MNP
Mason Creek and drain.
Nearest major estuary
(distance & direction)
Merriman Creek 5.5 km
northeast of MNP
2.2.2 MARINE HABITAT DISTRIBUTION
Mapping of habitats is important for understanding and communicating the distribution of
natural values within Marine National Parks and Sanctuaries, particularly as the marine
environment is not as easily visualised as the terrestrial environment (Parks Victoria 2003).
For management purposes, knowledge of the distribution and extent of habitats is required
to more effectively target management activities, including emergency response, monitoring
and research. Mapping of marine habitats provides a baseline inventory, allows the
identification of suitable monitoring sites and possible tracking of environmental change, as
well as identifying areas vulnerable to particular threats or suitable for recreational activities.
The main habitats present in Ninety Mile Beach MNP (Figure 15) include intertidal soft
sediment, extensive subtidal soft sediment, and the water column (Parks Victoria 2006e).
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