Assessing stream health with respect to ecological connectivity

We analyse stream health and some of its likely influences for a sample of 30 sites in 16 urban sub-catchments located in the Lower Brisbane River catchment and surrounding coastal catchments in southeast Queensland, Australia. We measure stream health with macroinvertebrate and fish diversity and abundance indicators. We specify three influences on stream health based on metrics generated using geographical information system techniques: an ecological connectivity index is created by aggregating two indicators of in-stream longitudinal connectivity; a land cover index is created by aggregating two indicators of land cover; and upstream sub-catchment drainage area. We use data envelopment analysis to create the indices, and stochastic frontier analysis to explain variations in the two stream health indicators. We rely heavily on dominance analysis, which is independent of the concept of a frontier and which provides the foundation for our ultimate evaluation of the ability of each site to convert ecological connectivity, land cover and upstream drainage area to stream health.