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HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 103
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4.3 Summary of rapid reach assessment 4.3 Summary of rapid reach assessment results - values and threats results - values and threats
The rapid reach assessment for the Strategy assessed environmental, social and economic values and
threats for river reaches in the Hawkesbury Nepean catchment. A number of these form the basis of
eight Management Themes (see Volume 1, section 2.3). The remaining values and threats inform the
detailed management actions in Appendix 4.2 and are summarised and mapped in this section.
Environmental Values
Riparian Vegetation
Riparian land with intact vegetation is critically important to the health of a waterway because it
provides:
• Organic matter to the river, a major food source for aquatic fauna
• A supply of woody debris within the river, which forms key habitat areas for many fi sh and
invertebrates
• A source of shade in upland areas which infl uences water temperature and light penetration
producing suitable conditions for aquatic fl ora and fauna
• Assistance in bank stabilization, reducing erosion in many areas.
Vegetated riparian land also acts as a buff er between the catchment and river so it can fi lter nutrients
and sediment from catchment run-off and reduce the impacts of land use on the river itself.
The Rapid Reach Assessment Panels determined the percentage cover class of riparian vegetation
cover through aerial photograph interpretation and through local knowledge of the river reach.
The panel determined that 79 (53%) of the assessed river reaches have >50% riparian vegetation cover, while 49 (33%) have <25% riparian vegetation cover.
River Condition
The condition of river reaches in the Hawkesbury Nepean has been assessed by the Geomorphic
Categorisation of Streams in the Hawkesbury Nepean (DLWC, 2001a). The assessment of river condition
incorporated available data on historical changes, fl oodplain linkages, sediment mobility, human disturbance and changes to river character (DLWC, 2001a). Based on these assessments river reaches
were classifi ed into one of four condition categories.
In the Hawkesbury Nepean 31% of reaches are rated as having near intact condition, 28% as having good condition, 22% moderate and 19% degraded. Most of the catchment (59%) is in Near Intact or
Good condition as the topography and geology of much of the catchment has limited the extent of
land use change and vegetation removal in these areas (DLWC, 2001a).
104 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY104 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY104
Recovery potential
The concept of recovery potential refers to the ability of a river reach to respond to disturbance or to
“bounce back” following disturbance. Reaches with a high recovery potential are generally those that
have minimal impact from human modifi cations and do not require intervention for rehabilitation
(DLWC, 2001a). River reaches with low recovery potential are generally characterised by extensively
altered geomorphic conditions and poor vegetation associations. Impacts of reservoirs and weirs can
also limit the recovery potential (DLWC, 2001a). These reaches are also often degraded as a result of
poor upstream condition.
The recovery potential of streams in the Hawkesbury Nepean catchment has been determined by the
Geomorphic Categorisation of Streams in the Hawkesbury Nepean.
31% of the river reaches assessed have a very high recovery potential. This large percentage is due
to the fact that over half of the catchment is bushland, much of this in deep sandstone gorges with
minimal threats. A further 14% has a high recovery potential, 27% has a moderate recovery potential
and 28% has a low recovery potential (DLWC, 2001a).
Sites of environmental signifi cance
This is a registered conservation asset and refers to the listing of specifi c sites on either the Register
of the National Estate, as National Parks, or as part of the Greater Blue Mountains World Heritage Area.
These sites do not necessarily refl ect ecological value however they indicate a recognised importance
and have high levels of environmental protection.
Signifi cant vegetation community
The catchment contains many rare, threatened and endangered vegetation communities. Many of
these communities are under threat from pressures such as clearing, urban development and weeds,
and many of them occur in riparian corridors.
The location and extent of vegetation community types in the Hawkesbury Nepean catchment
is covered by the Priority 5 Mapping Area (P5MA) vegetation mapping undertaken by the NSW
Department of Environment and Conservation and Department of Natural Resources (DEC and DIPNR
(2005) Native Vegetation Mapping Report Series 5).
Endangered Ecological Communities (EECs) listed under State legislation (Threatened Species
Conservation Act) and Commonwealth legislation (Environmental Protection and Biodiversity Conservation Act) within 30m of a watercourse have been identifi ed and extracted from the P5MA
information and mapped. River reaches were assessed in terms of the presence or absence of these
EECs.
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 105
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Social Values
Swimming
The degree to which a river reach is used for swimming can be infl uenced by a number of factors.
These may include the suitability of the waterway in terms of depth etc, level of accessibility, and
how clean the water is. Swimming is an important recreational asset and one that also requires the
maintenance of these set of conditions.
The Rapid Reach Assessment Panel used local knowledge to rate the frequency of swimming at each of
the river reaches.
57 (38%) of the river reaches assessed are used for swimming.
Recreational Fishing
The Rapid Reach Assessment Panel used local knowledge to rate the frequency of recreational fi shing
at each of the river reaches. The occurrence of recreational fi shing is not only an indicator of the
important social value of a river reach but can also provide an indication of the health of the aquatic
populations in that reach.
The highest levels of recreational fi shing occur generally in the lower reaches of the catchment,
focusing on the estuary and also the freshwater tributaries that support the native Australian Bass.
Popular recreational fi shing locations in the upper reaches of the catchment are associated with exotic
fi sh species such as Trout.
67 of the assessed river reaches (45%) were identifi ed as being used for recreational fi shing.
Boating
Two types of boating were investigated as social assets to a river reach, both motor boating and
non-motor boating. Non-motor boating included canoeing and li-loing. Motor boat use was
restricted largely to the estuary of the Hawkesbury Nepean and the wider rivers in the lower part of
the catchment. Non-motor boating however was widespread across the catchment. There was a relationship between public river recreation access points and the occurrence of other social value
activities such as boating.
46 (31%) of the assessed reaches are used for non-motor boating and 18 (12%) of the assessed reaches
are used for motor boating.
Scenic QualityThe perception of the scenic quality of a river reach and its landscape may diff er from one person
to another, however where there was a general consensus among Rapid Reach Assessment Panel
members of the level of scenic quality of an area it was recorded. Sydney Regional Environment Plan 20 (Hawkesbury Nepean River) covers the lower section of the catchment and identifi es areas of scenic
quality of regional signifi cance. Reaches in National Park or World Heritage Area were considered to be
of State Signifi cance in terms of scenic quality.
106 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY106 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY106
Economic Values
Irrigation
Water extraction from rivers ranges from basic riparian rights, which allow users to extract water for
stock and domestic gardens, to high use water extraction for broad scale irrigation or industry. The
Rapid Assessment Panel assessed irrigation water supply as an economic asset.
The river reaches of highest water extraction for broad scale irrigation or industry include the
Hawkesbury Nepean River, South Creek and the lower Wollondilly River.
Commercial Fishing
The Hawkesbury Nepean River supports the second largest commercial coastal fi shery of prawns,
oysters and fi sh in NSW with a wholesale value of $6.3 million annually. Commercial fi shing industries in
the Hawkesbury Nepean are restricted to the estuary, with a trout farm on the Marangaroo River in the
Upper Coxs Subcatchment being the only exception.
Tourism
Rivers often provide a draw card for tourists due to their range of recreational and aesthetic values. The
Rapid Reach Assessment Panels were asked to assess the level of usage of river reaches by tourists. The
major focus area of tourists in the catchment is the Hawkesbury Nepean estuary.
Land use
The Rapid Reach Assessment Panel determined the class of land use dominating beside each river
reach. Land use type is typically closely linked to land use value. High productivity areas such as
intensive irrigation areas or urban residential areas are generally of higher economic value than grazing
land or bushland.
The Hawkesbury Nepean River fl oodplains contain the most intensive irrigation areas in the catchment
and the South Creek subcatchment is dominated by urban development land use.
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 107
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Threats
Damaging access
Riparian zones are sensitive areas of the landscape, easily susceptible to damage such as riverbank
erosion, native vegetation degradation and weed invasion. Unrestricted access from cattle or humans
down river and creek banks can cause serious erosion and grazing can degrade native vegetation.
The Rapid Reach Assessment Panels used a combination of aerial photographs and local knowledge
of the reaches to rate the degree of damage to riverbanks as a result of unmanaged stock or human
access.
The Panels found that 35 (25%) of assessed river reaches had observable stock or human access
damage to more than 10% of the reach. A further 46 (31%) had focused human access damage.
Woody weeds
The Rapid Reach Assessment Panels used a combination of aerial photograph interpretation and local
knowledge of river reaches to determine a percentage class of woody weed invasion. The highest
levels of woody weed invasion were in the Nepean River near Camden, the Hawkesbury River between
Yarramundi and Lower Portland, Cattai Creek and South Creek.
20 (13%) of the assessed river reaches have woody weeds making up >50% of their vegetation cover.
The majority of the river reaches in the catchment have little or no woody weed invasion.
Some of the more common woody weeds across the catchment include Honey Locust (Gleditsia
triacanthos), Privet, African Olive, and various species of Willow.
Pest animals
Some species of pest animals have the ability to create visible physical damage to riparian zones if
present in large enough numbers. The rapid reach assessment panels identifi ed problem pest animals
on the river reaches and indicated the level of damage they were causing.
26 of the river reaches assessed recorded some level of damage from pest animals.
Some of the common pest animals noted included pigs, deer, goats, rabbits, and feral cattle.
Flow regulation
The catchment contains a large number of dams and weirs scattered throughout the river system. These structures alter natural fl ow regimes and interrupt sediment transport, having serious impacts on
downstream environments.
40 of the river reaches assessed are dammed for water supply and thus regulated. This equates to
883km of waterway.
Extraction
The Stressed River Assessment Report for the Hawkesbury Nepean Catchment was used to determine the
level of Hydrologic Stress for each of the subcatchments. Most of the subcatchments outside reserved
lands experience a high level of hydrologic stress, largely infl uenced by high levels of extraction.
108 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY108 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY108
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 109
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Riparian VegetationRiparian Vegetation
Environmental AssetsEnvironmental Assets
Fig. A2
110 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY110 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY110
River ConditionRiver ConditionAdapted from DLWC(2001a) Adapted from DLWC(2001a)
“Geographic Categorisation of streams in the“Geographic Categorisation of streams in the
Hawkesbury Nepean catchment”Hawkesbury Nepean catchment”
Environmental AssetsEnvironmental Assets
Fig. A3
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 111
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Environmental AssetsEnvironmental Assets
GeomorphicGeomorphicRecovery PotentialRecovery Potential
Adapted from DLWC(2001a)Adapted from DLWC(2001a)
“Geographic Categorisation of streams in the“Geographic Categorisation of streams in the
Hawkesbury Nepean catchment”Hawkesbury Nepean catchment”
Fig. A4
112 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY112 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY112
Sites of EnvironmentalSites of EnvironmentalSignifi canceSignifi canceFig. A5
Environmental AssetsEnvironmental Assets
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 113
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Fig. A6
Environmental AssetsEnvironmental Assets
Signifi cant Vegetation Signifi cant Vegetation CommunityCommunity
AAdapted from P5MA mapping; Tindall, D. et. al. (2005) AAdapted from P5MA mapping; Tindall, D. et. al. (2005)
Native Vegetation Map Report Series. No. 4. Version 2.2. Native Vegetation Map Report Series. No. 4. Version 2.2.
114 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY114 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY114
Social AssetsSocial Assets
Fig. A7 SwimmingSwimming
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 115
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Social AssetsSocial Assets
Fig. A8RecreationalRecreational
FishingFishing
116 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY116 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY116
Fig. A9
Social AssetsSocial Assets
Non-MotorNon-MotorBoatingBoating
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 117
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Fig. A10
Social AssetsSocial Assets
Motor Boating / Motor Boating / SkiingSkiing
118 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY118 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY118
Fig. A11
Social AssetsSocial Assets
Scenic QualityScenic Quality
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 119
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Fig. A12
Economic AssetsEconomic Assets
Irrigation Water SupplyIrrigation Water Supply
120 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY120 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY120
Fig. A13
Economic AssetsEconomic Assets
Commercial FishingCommercial Fishing
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 121
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Fig. A14
Economic AssetsEconomic Assets
TourismTourism
122 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY122 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY122
Fig. A15
Economic AssetsEconomic Assets
LanduseLanduse
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 123
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Fig. A16
ThreatsThreats
Damaging Access toDamaging Access toRiparian ZoneRiparian Zone
124 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY124 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY124
Exotic Plant SpeciesExotic Plant SpeciesRiparian Woody WeedsRiparian Woody WeedsFig. A17
ThreatsThreats
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 125
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Fig. A18
ThreatsThreats
Pest AnimalsPest Animals
126 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY126 HAWKESBURY NEPEAN CATCHMENT MANAGEMENT AUTHORITY126
Fig. A19
ThreatsThreats
Flow RegulationFlow Regulation
HAWKESBURY NEPEAN RIVER HEALTH STRATEGY 127
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Flow Modifi cation / Flow Modifi cation / Extraction
Adapted from Stressed Rivers Reporton the Hawkesbury Nepean
Fig. A20
ThreatsThreats