Floodwalls

Floodwalls are vertical or near‑vertical structures designed to protect urban areas, critical infrastructure, and low‑lying lands from floodwaters. Unlike sloping levees, floodwalls occupy a smaller footprint, making them suitable for densely built environments where space is limited. They are typically constructed from reinforced concrete, steel sheet piling, or modular block systems, and are anchored into the ground to resist hydrostatic pressure, wave action, and seepage.

The primary function of a floodwall is to act as a barrier that raises the effective height of a floodplain, preventing water from inundating protected zones. Designing a floodwall involves hydraulic analysis to determine design flood elevations, assessment of soil bearing capacity for foundations, and consideration of overtopping scenarios. Walls may include integrated drainage features, such as weep holes or relief valves, to alleviate pressure buildup during prolonged flooding.

Floodwalls are often combined with surrounding flood defense measures—such as berms, floodgates, and pumping stations—to provide a comprehensive flood risk management system. While effective in containing moderate floods, they can be vulnerable to extreme events that exceed design capacities, leading to overtopping or structural failure. Maintenance is critical; regular inspections for cracking, corrosion, and settlement help ensure long‑term performance.

Prominent examples include New York City’s East River floodwall, parts of the Netherlands’ room for the river program, and floodwall systems in coastal Japanese cities. Ongoing research focuses on improving resilience through innovative materials, adaptive designs, and integration with green infrastructure to enhance both protection and environmental compatibility.