The temporal and spatial distribution patterns of diatoms colonising artificial substrates were used to develop a model indicating different levels of degradation in urban streams of the Swan River, Perth, Western Australia. Diatom and algal based matrices were used to develop a multimetric index used to categorise the environmental condition of stream sites into four urban groups: (1) Streams in forested catchments with good to excellent ecological integrity and > lOkm from the estuary (2) Streams receiving estuarine water with partial stream degradation (3) Streams in proximity to...