GSI Design
Green stormwater infrastructure design is a process for making decisions about the type, sizing, and siting of GSI to meet stormwater management goals. The design phase of GSI typically involves a planning-level exploration of several proposed GSI design configuration options that meet stated performance objectives, such as percent runoff reduction. Once soils data has been incorporated into initial site locations and any additional soils sampling and analysis conducted, this design process continues with sizing individual GSI practices, scaling these practices to the project area, and modeling the runoff reduction achieved.
- What is GSI Design?
- Diagram: Multi-variable GSI Design Concept This diagram illustrates the conceptual relationship between (1) engineered and native soils (2) GSI depth (3) loading ratios and (4) design storms.
Design Process Steps: Introduction
Green stormwater infrastructure design involves: sizing GSI to meet run-off reduction targets; scaling GSI to the project area; and modeling GSI designs to evaluate performance. As a result of the design process, the team will have conceptual-level GSI design scenarios meeting specified performance targets, community preferences, and budgets.
The Role of Soils in GSI Design
This guide enables stormwater planning process participants to understand how native soils are connected to GSI design.
In the the siting and site soils analysis steps, a spatial analysis incorporating native soils data is used to identify priority locations from which site-specific soils data is collected and analyzed. The sizing step builds on these actions by combining native soils performance (hydraulic conductivity, or the ease with which water will move through soil) with other GSI design variables to determine optimal GSI sizing. Once sized, GSI practices can be scaled to the project area, considering variation in native soils. These configurations can then be modeled and evaluated, iteratively adapting designs to best take advantage of native soils properties to meet run-off targets.