Benson & Fallding, Brisbane Water National Park 
81 
The most frequent winds throughout the year are light southerly to southwesterly 
and northeasterly. On-shore winds predominate during the spring and summer, 
while westerly and northwesterly winds occur mainly in autumn and winter. Local 
and low pressure frontal storms, particularly from the southeast in summer, bring 
gale-force winds. 
Topography, geology and soils 
The study area is part of the Triassic Hawkesbury Sandstone plateau which 
covers much of the Sydney region (New South Wales Dept, of Mines, 1966). During 
its uplift this plateau was dissected by deep valleys which cut through the Hawkesbury 
sandstone to expose the underlying strata of the Narrabeen Group, also of Triassic 
age. The lower sections of these valleys have been subsequently drowned by rising 
sea level to give the present shallow estuaries of Mooney Mooney and Mullet Creeks. 
Stream patterns on the sandstone plateaux are dendritic but are influenced by the 
jointing patterns in the sandstone. Valley profiles are typified by cliffs of the more 
resistant Hawkesbury Sandstone, steep slopes (with angles of ca. 25°) from the under¬ 
lying Narrabeen Group and narrow valley floors or drowned river valleys. More 
resistant remnants of sandstone form higher peaks on the plateaux, such as Kariong 
and Wondabyne Trigs. The Hawkesbury Sandstone is composed mainly of lenti¬ 
cular beds of quartz-rich sandstone, with occasional shale and siltstone lenses 
(Standard in Packham, 1969). A variety of soil types is found. On ridges and slopes, 
soils vary from shallow skeletal siliceous sands to deeper duplex soils with a sand 
to sandy loam A horizon, and a sandy clay to medium clay B horizon. On ndges 
in the south of the Park, exposed shale lenses weather to light clay soils with grad¬ 
ational profiles. On plateaux (particularly in the north) distinctive yellow earthy 
soils are developed. These have gradational profiles and often are associated with 
ironstone nodules. 
The Narrabeen Group, composed in this area mainly of shales, underlies the 
Hawkesbury Sandstone. Exposures of Narrabeen Group vary, reaching a maximum 
in Strickland State Forest and Mooney Mooney Creek in the north, and decreasing 
to the south of the study area near Patonga. These rocks form deep clay-rich sous 
with duplex to gradational profiles. 
Small intrusions of Tertiary basaltic rock are found at Dillons Crater and the 
Woy Woy rubbish tip in the southeast of the study area. These intrusions weathei 
to deep dark clay soils (rich in iron and magnesium) with gradational or uniform 
profiles. 
Quaternary and Recent deposits of unconsolidated sands and silts occui along 
the major watercourses, e.g. Mooney Mooney Creek. 
Land use and human influences 
Attempts at agriculture in the Brisbane Water area were begun in the 1820 s 
but moved unsuccessful and were replaced by timber getting and boat building. 
These* reinaincil'themajo^ industries i,«o ,hc 20.1, ccn.ury when .hey were replaced 
by tourism and recreation, and increasing uibamzation (Stromera/., 19 ). 
In the Park there has been past logging activity, particularly along Mooney 
Mooney and Piles Creeks. Sand extraction on the banks of Mooney Mooney Cieek, 
upstream from the Pacific Highway bridge, no longer occurs, but was formerly 
extensive, 
The southern half of the Park has various ‘incursions’, private holdings, such as 
quarries, farms, a rifle range and a National Fitness Camp. Quarrying for sandstone 
is still active in the Girrakool-Kariong area, but not within the I ark. 
The main northern railway passes through the Park.along; the* ^ank of 
Mullet Creek and through a long tunnel to Woy Woy. A large settlci 
