Grey Infrastructure in the GGBI Framework

In the Green–Grey–Blue–Intelligent (GGBI) Framework, the Grey domain includes engineered structures and systems that convey, store, protect, or control water. Grey infrastructure forms the backbone of urban drainage, river engineering, stormwater management, and coastal protection.

Pipes & drains Culverts & tunnels Detention & storage Levees & floodwalls Weirs & spillways Coastal structures

Role of Grey Infrastructure

Grey infrastructure provides essential hydraulic and structural functions throughout water and urban environments. It plays a central role in:

Conveying stormwater, wastewater, and flood flows.
Providing storage, detention, or diversion during high-flow events.
Protecting developed areas from riverine and coastal hazards.
Managing drainage, street runoff, and combined sewer systems.
Stabilizing shorelines, channels, and coastal zones.

While traditional grey systems have focused on single functions (e.g., conveyance), modern practice emphasizes flexibility, integration, redundancy, and adaptation to climate-driven extremes.

Examples of Grey Infrastructure

Pipes, Culverts, & Tunnels

These structures form the underlying network for conveying stormwater and urban drainage. Their performance depends on slope, capacity, roughness, and maintenance.

Detention & Retention Facilities

Basins, tanks, surface ponds, and underground structures that store runoff during storms and release it in a controlled manner. They may also provide water-quality treatment.

Levees, Floodwalls, & Barriers

Structural measures used to protect flood-prone areas from river overflow, storm surge, and tidal inundation. Their design involves elevation, stability, overtopping, and seepage considerations.

Coastal & Shoreline Structures

Bulkheads, revetments, seawalls, groins, and breakwaters that modify wave energy, water levels, and sediment dynamics along coasts and estuaries.

Grey infrastructure is often the most visible and expensive component of water management systems. Its effectiveness increases when designed and operated together with Green, Blue, and Intelligent components.

Interactions with Green, Blue, and Intelligent Domains

Grey infrastructure interacts with other domains in ways that influence overall system performance:

With Green: Grey systems receive runoff from or work in parallel with Green measures. Coordinated planning can reduce pipe sizes, improve water quality, and lower maintenance burdens.
With Blue: Grey structures influence water levels, flows, storage, and sediment processes in rivers, estuaries, and coasts. Examples include tidal gates, training walls, and storm-surge barriers.
With the Intelligent layer: Sensors, models, and data tools improve monitoring, forecasting, and control of grey assets—from pump stations to urban drainage networks to coastal defenses.

In the GGBI Framework, Grey infrastructure is evaluated as part of an integrated portfolio that considers resilience, reliability, redundancy, and long-term adaptability.

Links to Applications on This Site

The Grey domain connects directly to:

Future updates may include case studies illustrating coordination between Grey, Green, Blue, and Intelligent elements.