Can allotment-scale rainwater harvesting manage urban flood risk and protect stream health?

The traditional management of stormwater with a singular focus on flood protection has resulted in the degradation of receiving waters. The health of urban streams is degraded by a suite of stressors, notably, the frequent disturbance due to stormwater runoff. We investigate the catchment scale implications of allotment scale rainwater harvesting, in terms of potential simultaneous benefits for stream protection and flood risk. We used an event joint probability approach to estimate flood risk for hypothetical catchments with varying degrees of urbanization and rainwater harvesting. We found that allotment-scale rainwater harvesting can provide moderate (but potentially significant) reductions to flood risk. To further reduce flood risk, attention should be given to decreasing the volume of rainfall which becomes runoff, by combining allotment-scale rainwater harvesting with a range of other stormwater techniques, such as infiltration and complementary application of larger-scale stormwater harvesting.

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