Regional councils in New Zealand are facing increasing pressure to address an array of contaminants and improve urban stormwater quality and reduce impacts on rivers and beaches. Contaminants like bacteria, metals and nutrients are pervasive and often exceed regulatory limits in a substantial percentage of samples collected from urban stormwater outfalls. To address these contaminants, catchment-scale stormwater quality improvement strategies are needed, as directed by the National Policy Statement for Freshwater Management. This paper presents the process and findings from multiple next-generation, quantitative stormwater quality planning efforts by municipalities along the West Coast of the United States including southern California and Washington state. The outputs from linked models to simulate baseline catchment conditions and the effectiveness of stormwater control measures are a key element of stormwater planning. The presented modelling approaches emphasize process-based models that are open source and public domain (LSPC, HSPF and SUSTAIN). The cost-optimization modelling provides a pathway toward developing high-efficiency stormwater quality programs and supporting development of more reasonable implementation schedules. Web-based tracking systems, which are also open domain, can facilitate a “hands on” environment for the public to understanding model outputs. During the implementation phase, web-based systems can also support tracking and demonstrating progress toward defined schedules and milestones. Combined, these tools can transform stormwater programs from relying on qualitative, anecdotal data to adopting quantitative analyses that allow for targeted, efficient and transparent programs with multiple benefits for the public. The National Policy Statement for Freshwater Management provides an impetus and opportunity for regional councils to adopt stormwater quality improvement programs that provide substantial benefits to both ecosystems and communities.