Green Stormwater Infrastructure (GSI) Explained

As cities grow and impervious surfaces expand, managing stormwater runoff becomes increasingly critical. Traditional “gray” infrastructure – like concrete pipes and underground detention systems – can only do so much. Enter green infrastructure and its more targeted counterpart, green stormwater infrastructure (GSI): sustainable, cost-effective approaches that work with nature to manage stormwater, reduce flooding, and improve water quality.

In this post, we’ll cover:

• What green and green stormwater infrastructure are
• Key benefits for property owners and municipalities
• Common types of GSI
• How it supports stormwater compliance
• Why it’s becoming the gold standard for urban planning

What Is Green Infrastructure (and GSI)?

Green infrastructure refers to a broad category of nature-based systems designed to deliver environmental benefits in urban settings – from tree canopies and open space networks to green roofs and parks. A specialized subset of this is green stormwater infrastructure (GSI): systems engineered specifically to manage stormwater runoff using natural processes.

GSI slows, absorbs, filters, and reuses stormwater at its source – rather than simply diverting it into storm drains. Examples include bioswales, rain gardens, green roofs, permeable pavement, and constructed wetlands.

🔍 Terminology Tip:
While “green infrastructure” includes a range of environmentally beneficial practices, green stormwater infrastructure (GSI) specifically addresses stormwater runoff in urban and suburban environments.

Benefits of Green Stormwater Infrastructure (GSI)

Green stormwater infrastructure offers benefits that go far beyond water management. Here are key reasons why GSI is gaining traction among property developers, municipalities, and commercial property managers:

1. Stormwater Control & Flood Reduction

GSI captures rainfall close to where it lands, reducing peak flow rates and alleviating pressure on gray infrastructure. This helps prevent localized flooding and erosion during heavy storms.

2. Improved Water Quality

Rain gardens, bioswales, and other green infrastructure systems naturally filter out oil, sediment, and heavy metals before runoff reaches nearby streams, lakes, or storm drains – supporting cleaner waterways and aquatic habitats.

3. Enhanced Property Value

Green infrastructure features double as landscape improvements. They enhance curb appeal, increase property values, and contribute to healthier, more livable communities.

4. Urban Heat Island Mitigation

Vegetated GSI elements – like green roofs and tree canopies – help cool urban areas, lowering surrounding temperatures and reducing energy costs for building owners.

5. Regulatory Compliance

Many jurisdictions now require or incentivize green stormwater infrastructure as part of development and redevelopment projects. GSI plays a crucial role in meeting MS4 (Municipal Separate Storm Sewer System) and NPDES (National Pollutant Discharge Elimination System) permit requirements.

Types of Green Stormwater Infrastructure

Green stormwater infrastructure can be customized for different site conditions, project goals, and space constraints. Common GSI techniques include:

🌿 Rain Gardens

Shallow, vegetated depressions that absorb and filter stormwater runoff from roofs, sidewalks, and streets.

🌀 Bioswales

Gently sloped, landscaped channels that convey and treat runoff while promoting infiltration.

🌧 Green Roofs

Building rooftops designed with soil and vegetation layers that absorb rainfall and reduce roof runoff.

🧱 Permeable Pavement

Surfaces made of porous materials – such as pervious concrete or permeable pavers – that allow stormwater to seep into the ground rather than flow into drains.

🪷 Constructed Wetlands

Engineered wetland systems that use natural processes to treat and retain stormwater on site.

🛢 Rainwater Harvesting Systems

Barrels or cisterns that collect runoff from rooftops for reuse in irrigation, toilet flushing, or industrial applications.

GSI and Stormwater Compliance

Green stormwater infrastructure is increasingly required in site development plans to meet local, state, and federal stormwater regulations. If you’re involved in construction, site redevelopment, or property management, implementing GSI can help you:

• Meet retention and water quality goals
• Avoid non-compliance penalties under MS4/NPDES
• Lower long-term drainage costs
• Qualify for tax credits or green building incentives
• Improve community relations by investing in visible, eco-friendly solutions

Partnering with a licensed stormwater professional ensures your green infrastructure features are properly designed, installed, and maintained to function long-term – and remain compliant.

Contact us today at (410) 231-3455 to learn more.

Green Infrastructure vs. Green Stormwater Infrastructure: What’s the Difference?

While the terms are often used interchangeably, green infrastructure is a broader umbrella that can include parks, open space networks, and urban forestry. Green stormwater infrastructure (GSI) is more specific – referring to engineered solutions that treat and manage stormwater where it falls. Both approaches are essential for building climate-resilient, livable communities.

Green Infrastructure: A Smart Investment for Sustainable Growth

Green infrastructure – especially GSI – is more than a buzzword. It’s a critical solution for sustainable development, climate resilience, and regulatory compliance. Whether you’re retrofitting an existing site or designing a new development, green stormwater infrastructure offers long-term environmental and financial returns.

Want to learn how GSI can work for your project or property?
Reach out to our stormwater team today for a site assessment or compliance consultation.