The Lugeon Test: Methodology, Interpretation, and Applications in Geotechnical Engineering

 "Gray" infrastructure, also known as hard infrastructure or built infrastructure, refers to traditional, engineered structures designed to manage water flow and protect areas from floods. These solutions are typically made from materials like concrete and steel.

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Key characteristics and examples of gray infrastructure include:

• Dams and reservoirs: Structures used to impound or store large volumes of water, creating reservoirs that can manage flood flow by releasing water slowly over time.
• Levees, dykes, and floodwalls: Earthen embankments or concrete walls built to confine rivers within artificial banks, protecting developed areas from floodwaters. While they protect some areas, they can also exacerbate flooding in others and shrink natural floodplains.
• Diversion canals (traditional): Human-made channels used to divert floodwaters away from developed areas, though these can also be designed as "eco-engineered" solutions that complement natural systems.
• Channel modifications/channelization: Increasing river channel carrying capacity for quicker floodwater passage, often involving straightening a river's path, which can lead to losses in ecosystem services.
• Gutters, drains, pipes, and tunnels: Conventional stormwater infrastructure in urban areas designed to redirect water away from developed areas to nearby water bodies.

Compared to nature-based solutions, gray infrastructure has been the dominant approach to flood management for decades. It offers advantages such as deep industry knowledge and high performance certainty and control. However, it also has limitations, including high costs, ecological disruption, and the risk of catastrophic failure under extreme conditions. In the context of climate change, conventional gray stormwater infrastructure is increasingly unable to handle more extreme precipitation events. There can also be challenges in implementing nature-based solutions due to decades of familiarity and perceived lower costs of gray infrastructure, as well as the complexity of modeling the benefits of nature-based solutions.