Stormwater management planning at the watershed-scale to meet water quality objectives is a complex endeavor typically focused on identifying where stormwater control measures (SCMs) can go in the watershed and which ones are needed to provide adequate protections. Because funding for SCMs can be limited, decision-making over which SCMs are pursued for construction is highly important to ensure that money is well spent. However, unpredictable factors can potentially make any SCM project infeasible despite its inclusion in a plan and regardless of its potential impact or cost-effectiveness. Additionally, producing a watershed-scale management plan and the overall cost of that plan is associated with high sensitivity related to many variables including (but not limited to) the scale of assessment, the level of project detail included, and the way projects are prioritized. Previous planning efforts have often relied upon watershed-scale optimization to discern an overall least-cost solution to meet compliance goals. However, a singular solution is highly influenced by cost functions that may not always be realistic and does not offer flexibility when SCMs identified in the solution set are determined to be infeasible. The limitations of optimization and the unpredictable nature of SCMs moving from plans to construction have been addressed with the preSIP platform developed for the Upper L.A. River (ULAR) Watershed Group. The preSIP has overcome the issues and complexities mentioned to produce an updateable plan within an adaptable platform that assesses compliance at a watershed scale, provides realistic projects with engineering details, and organizes planning around alternative pathways that represent different value systems to highlight tradeoffs for the member agencies of the ULAR Group. This presentation will highlight the modeling process taken in developing the preSIP platform, the alternative pathways provided to the Group, and the cost savings and tradeoffs realized when taking this type of approach.
