Waterway ecology

It is important to keep as much of a river network as natural as possible to ensure that the catchment and river condition can be maintained. In Ku-ring-gai much of the urban development is concentrated along the ridgeline areas, with the lower parts of the catchments being dominated by protected areas such as national parks and significant estuaries. Maintaining natural channel design wherever possible allows ecological, geomorphic and hydrological processes to be maintained, and minimises the degree of negative impact on the downstream protected areas.

Riparian vegetation

The composition of native riparian plant communities varies with location and environmental factors. The increased soil moisture levels in riparian areas favour the development of particular communities which may differ quite considerably in composition from those in adjacent upland areas, particularly if these areas are much drier. Riparian vegetation communities influence both the biological and physical components of the system.

They do this by:

  • providing food and habitat for terrestrial and aquatic organisms;
  • providing refuge for organisms during times of drought;
  • affecting water temperature and light levels;
  • affecting water quality by trapping sediments and nutrients;
  • influencing bank stability, sedimentation and erosional processes and
  • influencing hydrology by affecting overland and subsurface flows.

Ku-ring-gai Council has prepared a native riparian species list (pdf. 1MB) which can be used for identification and revegetation.

Riparian weeds have very high dispersal potential due to the connective nature of waterways. In particular, water weeds can:

  • Alter dissolved oxygen levels, reducing water quality.
  • Restrict recreational activities and access in waterways.
  • Displace natural vegetation and impede biodiversity.
  • Block channels and irrigation equipment.

Wherever possible, riparian weeds should be managed and preference should be given to native revegetation. Information on common weeds can be found on Sydney Weeds Communities  and the NSW Department of Primary Industries.

Riparian fauna

Many different species live in the creeks and riparian areas around Ku-ring-gai. Some of the most common native species include:

water-dragon  striped-marsh-frog

Eastern Water Dragon

Intellagama lesueurii

Photo credit Hande Tekin

Striped Marsh Frog

Limnodynastes peronei

 water-eel.png  sydney-crayfish

Long finned eel

Anguilla reinhardtii

Sydney Crayfish

Euastacus australasiensis

 long-neck-turtle  brush-turkey

Long neck turtle

Chelodina longicollis

Brush Turkey

Alectura lathami

 lyre-bird  sacred-kingfisher

Lyrebird

Menura novaehollandiae

Sacred Kingfisher

Todiramphus sanctus

Amongst the diverse fauna found within Ku-ring-gai’s creeks are a few commonly observed invasive species. For example:

Gambusia (mosquito Fish) Gambusia affinis

Carp Cyprinus carpio

NZ Freshwater Snail Potamopyrgus antipodarum