Bridging the Stormwater Management Gap: Integrated Watershed Master Planning for Water Quality, Flood Control, and Environmental Restoration
The City of San Diego (City) has developed the Chollas Creek Watershed Master Plan (WMP), which provides a comprehensive assessment of drainage infrastructure improvements, and water quality best management practices (BMPs) necessary to meet applicable storm water regulations and level of service requirements. The WMP is also intended to promote stream restoration as part of the drainage improvements. Traditionally, water quality compliance planning, infrastructure assessments, and stream restoration planning have been conducted in parallel due to differing timelines, funding sources, and lead agencies. The City proactively identified the need to collectively assess and prioritize stormwater projects that may satisfy multiple management objectives and reduce overall costs through optimized planning and implementation.
The critical foundation for the WMP was the recent collection of high-resolution geospatial data, allowing for rapid characterization of drainage patterns and BMP opportunities using geospatial processing algorithms. The prompt generation of new data sets with high levels of accuracy facilitated the development of design-level representations at the watershed scale—which ultimately allowed for a more finely tuned and lower-cost solution than originally developed in the water quality improvement plan (WQIP). Furthermore, the incorporation of drainage infrastructure improvements allowed the City to strategically prioritize “bundled” projects to capitalize on potential synergies and cost-sharing.
The primary goal for the WMP water quality component was to identify specific project-by-project structural priorities to meet each regulatory milestone. The multi-tiered modeling and optimization framework used has the capability to dynamically assess the water quality benefits of specific projects against one another and accounts for the complex, interdependent nature of implementing BMP retrofits within a highly urbanized environment. Fundamental enhancements to the water quality planning process were incorporated to create a robust linkage between watershed-scale regulatory compliance strategies and on-the-ground implementation, including: identifying precise BMP locations, refining BMP representations for localized constraints, and incorporation of innovative and emerging technologies (e.g., retrofitting BMPs with real time controls to assist with flood management). The resulting prioritized projects highlight the necessity of linking watershed-scale planning with site-scale design to achieve a truly representative and “shovel-ready” compliance solution.
The primary goal of the stream restoration component was to find opportunities where drainage improvements (e.g. removal of concrete lining or channel widening) could be combined with creating or enhancing riparian habitat. Expanding riparian habitat within the WMP served a number of functions including: (1) enhancing water quality, (2) creating additional wildlife habitat, and (3) enhancing the visual character of the surrounding community.
The WMP provides the City with a comprehensive database for improvements needed in the watershed, and facilitates a more efficient use of funds and resources to meet multiple stormwater management objectives at the most rapid pace towards compliance possible. Ultimately, the output of the WMP provides the City with a web-based roadmap that is prioritized to implement high-impact and high-efficiency projects first, leaving less desirable projects for later implementation.
Eric Mosolgo, P.E. is a Senior Civil Engineer with the City of San Diego's Storm Water Division. He is leading efforts to develop the City's Offsite Alternative Compliance Program, and has served as the municipal project manager for development of the City's Watershed Master Plan. Eric's areas of expertise include LID BMP implementation, hydromodification management, watershed master planning, and floodplain analysis. He earned a Masters Degree in Civil Engineering from the University of Kentucky and has worked in the San Diego region since 1998.
Chad Helmle is Vice President of Integrated Watershed Management at Tetra Tech, where he leads a group of talented and energetic stormwater engineers and scientists. His group has demonstrated a tremendous will to innovate across the entire spectrum of the stormwater market and strives for outcome-oriented solutions. He is working hard to help our industry achieve a seamless alignment between planning, implementation, and monitoring. Mr. Helmle has a penchant for lengthy (but entertaining) stories. He offers a general apology for those in the room that he has trapped in the hallways while delivering animated regaling of his team’s latest adventures with models, BMPs, or some other nerdy analytical thing. Next round is on him.
Brendan Hastie is an Associate Principal in the Water Resources Division for Rick Engineering Company. He earned his Bachelor of Science in Civil Engineering from Penn State University and is a registered Civil Engineer. He has specialized in water resource engineering for the past 17 years. He is a member of the Technical Advisory Committees for the County of San Diego LID Handbook and Stormwater Capture and Use Feasibility Study, City of San Diego Alternative Compliance Program, and Member of the San Diego River WQIP Consultation Panel. He has prepared numerous GIS-based Watershed Master Plans throughout Southern California.