Center for Watershed Protection. 2017. Stormwater Performance-Based Credit Calculator. Crediting Framework Product #6 for the project Making Urban Trees Count: A Project to Demonstrate the Role of Urban Trees in Achieving Regulatory Compliance for Clean Water. Center for Watershed Protection, Ellicott City, MD. The Center for Watershed Protection Developed a Stormwater Performance Based Credit for tree planting. This national credit can be adopted by regulatory agencies who wish to offer a science-based credit that encourages greater use of tree planting for meeting stormwater management requirements. The Stormwater Performance Based Credit Calculator allows the user to calculate runoff, nutrient, and sediment reduction for tree planting scenarios for a specific storm event based on this credit.