Low Impact Development - Tools and Calculators
Runoff Reduction Calculator - developed by the Center for Watershed Protection (CWP) and the Chesapeake Stormwater Network (CSN)
The Runoff Reduction Method is an innovative system for stormwater design that focuses on Best Management Practices’ (BMPs’) capacity to reduce overall runoff volume as well as remove pollutants. The method also incorporates built-in incentives for Low Impact Development, such as preserving forests and reducing soil disturbance and impervious cover. The CWP and CSN have also been working with the Virginia Department of Conservation and Recreation (DCR) to integrate the Runoff Reduction method into proposed stormwater regulations and an updated stormwater management handbook, and have developed Excel-based calculators for estimating runoff reduction for new development and redevelopment.
Links to Runoff Reduction Methodology:
- Technical Support for the Bay-Wide Runoff Reduction Method
- Technical Memorandum: The Runoff Reduction Method
Links to the Virginia DCR calculators:
- General Overview and Instructions
- Stormwater Compliance Flowchart
- BMP Design Tables
- Runoff Reduction Documentation
- Land Cover Guidance
- Instructions for Runoff Reduction Calculator
- Runoff Reduction Calculator (Excel) – New Development
- Runoff Reduction Calculator (Excel) – Redevelopment
Green Infrastructure Whole-Life Cost Tool - developed by the Water Environment Research Foundation
The whole life cost (WLC) models are a set of spreadsheet tools that have been developed to facilitate a whole life costing approach for stormwater BMPs and LID practices, including estimation of capital costs as well as operation and maintenance costs. Users of the tools have the choice of operating in one of two operational modes: Generic (Default) Application, where the user can generate costs with minimal inputs to make planning-level cost estimates; and Site-Specific Application, or User-entered Engineer’s Estimate, where the user can custom enter values for virtually every component tracked by the model (system design and sizing, capital costs, and maintenance costs).
Links to the Whole-Life Costing Tools:
- Users Guide
- Cisterns
- Curb-contained Bioretention
- Extended Detention Basins
- Green Roofs
- In-curb Planters
- Permeable Pavement
- Rain Gardens
- Retention Ponds
- Swales
National Pollutant Removal Database, Version 3 (2007) - developed by the Center for Watershed Protection
The National Pollutant Removal Performance Database was updated in 2007 to version 3 to include an additional 27 studies published through 2006. The updated database was statistically analyzed to derive the median and quartile removal values for each major group of stormwater BMPs. The data are presented as box and whisker plots for the various pollutants found in stormwater runoff.
Links to the Database:
- Supporting Documentation
- Database (Access)
Other Tools and Calculators
Green Values Stormwater Calculator - The National Green Values Calculator is a tool for comparing the performance, costs, and benefits of Green Infrastructure, or Low Impact Development (LID), to conventional stormwater practices.
i-Tree - i-Tree is a software suite from the USDA Forest Service that provides urban forestry analysis and benefits assessment tools. The i-Tree Tools help communities of all sizes to strengthen their urban forest management and advocacy efforts by quantifying the structure of community trees and the environmental services that trees provide.
Tree Benefit Calculator - The Tree Benefit Calculator allows anyone to make a simple estimation of the benefits individual street-side trees provide. This tool is based on i-Tree’s street tree assessment tool called STRATUM. With inputs of location, species and tree size, users will get an understanding of the environmental and economic value trees provide on an annual basis.