Riparian vegetation change on the Clarence River floodplain

The natural streamside levees on the floodplain of the Clarence River in subtropical eastern Australia were occupied by riparian rainforest prior to European settlement. They were almost completely cleared for agriculture over a ten-year period from 1857 as a direct consequence of changes to land ownership laws. The floodplain is now a highly developed landscape, with the riverside levees occupied by roads, houses and agriculture, with minimal remnant vegetation. Comparison of 343 sites from 1942 and 2001 aerial photographs using GIS show that there has been an increase in overstorey riparian vegetation density and riparian width, both from very low bases. Ground surveys record that the overstorey riparian vegetation is predominately native with a weedy mid-stratum. Species diversity is low and targeted plantings may be required to provide a pool of rainforest species to start the slow process of recreating this important area of biodiversity. The majority of the increase in the width of riparian vegetation is due to the streams in the floodplain becoming narrower. This is caused by a combination of stream meander and infrastructure protection works. This study highlights the interaction of erosion, stream meander, infrastructure protection and riparian vegetation, and the implications for those managing floodplain streams.