The urban stream syndrome is a common occurrence worldwide where waterways are degraded physically and ecologically following catchment urbanisation. The primary driver of degradation is recognised as excess stormwater runoff from urban catchments. To add to this, wastewater treatment plants can significantly increase streamflow in waterways. To address increased flow volume, and altered flow pattern, requires demonstrating what values are lost for each development scenario. There was previously no formal method to assists planners, stormwater designers and waterway managers, despite the availability of methods for similar impacts such as from dams and storages. Drawing upon non-urban analogues, we developed an urban streamflow evaluation and amelioration method to explicitly link waterway values (social, ecological and geomorphic) to development scenarios streamflow, through the use of hydrologic and hydraulic metrics. The method has been applied to two case studies in western Sydney, demonstrating the loss of values associated with ‘business-as-usual’ approaches to stormwater management, and highlighting opportunities. The method can be applied across urbanising and urban catchments to inform controls on urban streamflows (what flows to keep out of the waterway), ultimately informing urban planning, drainage design and waterway management.