Document Type

Conference Proceeding

Publication Date

2004

Journal Title

American Water Resources Association, Riparian Specialty Conference, June 28-30, 2004, Riparian Ecosystems and Buffers: Multi-Scale Structure, Function, and Management (Olympic Valley, California, 2004)

Keywords

riparian buffer, rainforest, eucalyptus globules, sediment, phosphorus, nitrogen

Abstract

Riparian vegetation can trap sediment and nutrients derived from hillslopes. Most research into the effectiveness of riparian buffers has been experimental and little quantitative data exists on performance under natural field conditions. This study reports on grass and tree buffer performance under natural rainfall conditions in two contrasting Australian environments. Buffers receiving runoff from hillslopes cropped with bananas were monitored over a 4-year period in the wet topics of Far North Queensland (FNQ). Runoff, bedload and suspended loads were measured leaving the crop and leaving 15 m wide dense grass and remnant rainforest riparian buffers. The grass buffer was able to trap >80% of incoming bedload and between 30 and 50% of the suspended sediment and nutrient loads. An adjacent rainforest buffer acted as a temporary store of bedload, and a source area for suspended material. Grass and plantation Eucalyptus globulus buffers receiving runoff from grazed pasture were monitored over a 4-year period in a Mediterranean environment of SW Western Australia. Subsurface flow dominated nutrient and sediment transport in this location. A key result was the seasonal difference between the grass and E. globulus buffers. Sediment and nutrient transport occurred throughout the year in the E. globulus buffer, but only in the winter in the grass buffer. Half the annual loads moving within the E. globulus buffer were transported during intense summer storms. This study demonstrates the benefits of grass buffers, particularly on sloping tropical cropped land and identifies limitations on the effectiveness of tree buffers, although these may have ecological benefits.