The Future of Santa Cruz County Stormwater: Strategic Planning in the Cloud
To envision the future of stormwater in their communities, municipal stormwater managers must plan strategic treatment programs to meet their local needs and improve climate change resiliency, all while spending public dollars wisely. Beyond implementation alone, they must communicate the environmental and human impact and fundamental value of their program to municipal stakeholders, funding sources and the greater community. While data-driven prioritization analyses are often used, the industry status quo lies in time-intensive, static, desktop-based results. As soon as the input data changes, results are out of date, PDF plans are stuck on the shelf, and stormwater managers are back to square one. By its very nature, strategic planning needs to be a flexible, iterative process that can be updated as projects are completed, new science research is published, and new technologies are developed.
In 2017, the County of Santa Cruz adopted a cloud-based geospatial software solution to do just that. Leveraging a catchment-scale urban runoff and pollutant loading model to establish a quantitative baseline of their local stormwater condition, the County delineated a network of urban catchments to show how runoff is linked to the specific waterway to which it drains. Mapped comparisons of current stormwater runoff and pollutant loading rates across catchments, supported by the fully distributed modeling approach, allowed the County to interpret and quantify their stormwater priorities on both hydrologic and jurisdictional scales. The County was interested in analyzing their data by the political boundaries of Supervisorial Districts rather than traditional watershed delineations. Results indicated that Districts 1 and 2 – predominantly urbanized areas adjacent to the cities of Santa Cruz, Capitola, and Watsonville – provide the greatest opportunities for potential stormwater capture and pollutant load reduction.
Leveraging the same online planning scenario tool, the County ran a series of eight “what if” scenarios to quantify the potential environmental return of stormwater investments such as disconnection of impervious areas, structural BMP implementation, and improvements to road condition and street sweeping practices. Parcel-scale impervious disconnection achieved by non-structural low impact development strategies was found to reduce stormwater volume by 12.1% and particulate pollutant loads by 9.6% in District 1, while reducing District 2 volume and pollutant loads by 6.6% and 4.5%, respectively. Decentralized structural BMPs, which route water to features for infiltration and treatment, were shown to provide substantially larger reductions – up to 20.9% volume and 16.5% particulate load reductions in District 1, with 9.5% and 6.6% in District 2. Street sweeping and road condition improvements provide the particulate pollutant reductions of 35.0% County-wide, while a combination of decentralized structural BMP controls and optimized street sweeping were shown to reduce particulate pollutant loads by nearly 50% in District 1.
The County now plans to pair the modeled results with a cost analysis to develop a multi-phased implementation approach to improve stormwater and better advocate for required funding. Iterative, spatially explicit quantification gives the County flexibility to test various approaches on a small jurisdictional and hydrologic scales to determine the effectiveness and efficiency of implementation, before expanding to a wider scale. As the County continues to implement strategic management actions, environmental opportunities will shift, and new spatial patterns will arise. With the adaptive cloud-based software, the County can continue to ask “what if” to determine priorities and articulate both the progress and the intrinsic value of their stormwater program to managers, regulators, elected officials, funders, and the public as their vision of the future of clean stormwater becomes a reality.