Monitoring the hydrochemical efficiency of urban stormwater treatment
devices is not straightforward as the traditional, automated, In
urban areas, efficient drainage of impervious surfaces means that
polluted stormwater is frequently delivered to streams. Commonly,
catchment urbanization can increase runoff frequency by a factor
of 10 or more, as the effective imperviousness - the proportion of
the catchment that consists of impervious surfaces drained to streams
- is increased. This causes a decline in stream health.
To decrease runoff frequency, effective imperviousness must be reduced.
This requires urban drainage systems to be redesigned, using techniques
such as infiltration and rainwater harvesting, so that stormwater
from small rain events is not piped directly to streams but instead
is infiltrated, reused or retained. We have developed scenarios that
explore alternative urban drainage systems appropriate for a small
partly urbanised catchment in Melbourne's east. These scenarios incorporate,
biofiltration basins, swales and dual purpose rainwater tanks that
supply water for householders. Our results suggested that sufficient
reductions in effective imperviousness and runoff frequency are possible
to achieve improvements in stream health.