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National Riparian Lands Research & Development Program

Riparian lands play a vital role in a healthy, productive landscape. They offer a specialised habitat and corridors linking other parts of the landscape, providing a refuge for plants and animals in times of environmental stress, and becoming refuges from which species can move out and recolonise adjacent areas when more favourable conditions return. They can exert a strong influence on in-stream health, and have the potential to affect water quality and quantity. They can influence the shape and stability of river channels, and hence break outs and flooding. Riparian lands also have special cultural, recreational and aesthetic significance, particularly when close to urban areas.

In Australia, poor management, or lack of management, has led to the substantial degradation of riparian lands. The removal, fragmentation and drastic alteration of vegetation cover, combined with changed flow regimes has increased the incidence of bank erosion, resulting in a loss of agricultural land during floods, changes to river shape and decreased water quality. The economic costs of the poor management of riparian lands are significant. 10% of the $450 million spent each year on water quality treatment for human use may be attributed to the degradation of riparian lands. Remedial works, such as protective infrastructure and flood mitigation measures designed to prevent or reverse riparian degradation, represent a substantial cost to landholders, communities and governments, and is estimated at costing $100 million per year.

These estimates take no account of production losses, nor the environmental services provided by riparian lands and healthy riparian vegetation. In 1993, the Land & Water Australia Board (then the Land & Water Resources Research & Development Corporation) agreed to fund the National Riparian Lands R&D Program. This followed a study that showed although riparian zone processes were thought to be crucial for healthy rivers, there was very little published Australian data about these processes, or about how riparian land should be managed to maintain its key functions.

Key Findings

Some of the key findings from the National Riparian Lands R&D Program, several not anticipated at its commencement, are:

  • identifying the different sources of sediments in streams and designing appropriate management responses;
  • understanding of the main mechanisms by which streambanks erode, and design of effective management responses to them;
  • the effectiveness of riparian vegetation, especially grass filter strips, in trapping sediment and attached nutrients;
  • understanding of the mechanisms and quantification of the extent to which the roots of riparian vegetation roots reinforce and stabilise streambanks;
  • the minor contribution of riparian trees to surcharge and slumping of streambanks, contrary to supposition;
  • understanding the effects of riparian vegetation on flood peaks and duration within a catchment
  • showing the importance of riparian inputs from native vegetation to streams under natural conditions, and the deleterious effects of clearing and over-grazing
  • identifying nitrogen as the limiting factor of in-stream growth in many situations;
  • demonstrating for the first time the role of shade in controlling growth of nuisance aquatic plants in waterways, even under conditions of elevated nutrient levels;
  • the necessity to replant streambanks with native species since aquatic organisms cannot utilise the C4 sources of carbon provided by exotics such as para grass and sugar cane;
  • showing the importance of in-stream habitats such as large woody pieces and root armouring of banks, and the role of native vegetation in providing these;
  • the role of shade from riparian vegetation in controlling stream water temperature:
  • demonstrating the deleterious nature of uncontrolled stock access to streams due to large inputs of nutrients in dung and urine, trampling of vegetation and pugging of soil at the water’s edge;
  • showing how strategic management of grazing can be used to improve productivity and recoup fencing and watering costs while improving environmental management;
  • developing and demonstrating practical methods for riparian fencing, alternative water point development, and re-vegetation; and
  • demonstrating the importance of integrating social science with biophysical science so that the range of factors that impact on people and their behaviour in managing riparian areas is recognized and acted upon.

Many of these findings have been presented in quantified models, look-up tables or other forms that enable river managers and those assisting landholders to use their local data to develop specifications for a particular site or project

id: 3703 / created: 09 September, 2009 / last updated: 09 September, 2009