An Innovative Stormwater Best Management Practice Decision Support System for Quantifying and Optimizing Load Reductions and Costs in Los Angeles

Protecting environmental quality requires a comprehensive approach that heavily relies on our ability to confidently predict or forecast impacts, evaluate the ability of natural systems to absorb impacts, and determine the combination of options that will provide an acceptable level of protection and/or restoration. These forecasts, when accepted, can help stakeholders to understand the potential cost or implications of restoration options and guide the development of effective protection strategies that can mitigate and prevent adverse impacts. Forecasts, which are typically based on combinations of modeling and analysis, must be designed to be sensitive to changes in the watershed and to in-stream responses. The difficulty with forecasts is that they are just predictions based on what we know now and what we believe might happen in the future. That is why environmental protection studies emphasize rigorous science-based approaches that can build confidence in forecasts. Building on an extensive body of relevant studies in the Los Angeles region, including monitoring, model development, and regional model parameterization efforts, this study is designed to develop and apply a Best Management Practice Decision Support System (BMPDSS) for the evaluation of alternative storm water best management practices (BMPs) and Low Impact Development (LID) methods. The system allows managers to evaluate the ability of various BMP scenarios to provide necessary flow volume and pollutant load reductions for Total Maximum Daily Load (TMDL) implementation and optimizes the scenarios based on benefits and costs. The approach is designed to provide guidance for a public incentive plan for implementing onsite BMP/LID techniques. The framework developed in this study provides a technically defensible and repeatable basis for evaluating quantitative measures associated with alternative BMP implementation plans. The BMPDSS represents an advanced method for simulating BMP processes and analyzing benefits (e.g., load reductions). Results of this study provide an interesting glimpse into the most relevant and economical BMPs for typical land uses in the Los Angeles watershed.