Flooding poses a consistent threat to communities worldwide, historically prompting efforts to control and manage water movement. While large-scale engineering projects have long been the primary method, they are not the only solution for managing flood hazards. Nonstructural flood control focuses on mitigating the damage and disruption caused by floods rather than physically altering the flow of water. This approach centers on modifying the relationship between human settlements and the natural environment.
Understanding Nonstructural Flood Control
Nonstructural flood control refers to the policies, practices, and systems that reduce flood damage without relying on constructed barriers or channel modifications. The core concept is managing the impact of a flood event on people and property, not the floodwaters themselves. This is achieved by modifying human behavior, land use, and development patterns in flood-prone areas.
The approach is fundamentally a policy-based, preventive strategy, seeking to limit exposure to the hazard before it occurs. Instead of building higher defenses, nonstructural methods aim to make communities more resilient to water intrusion. They acknowledge that while floods are natural events, the resulting disaster is often a consequence of human choices regarding where and how to build.
Common Strategies and Implementation
Land use planning is a primary tool, restricting or guiding development in high-risk zones like riverine floodplains or coastal areas. Zoning ordinances may prohibit construction of new residential or commercial properties in the highest flood hazard areas. This measure reduces the number of structures and people exposed to inundation, lowering the potential for damage during a flood event.
Building codes and regulations further implement this strategy by mandating specific construction techniques for buildings that remain in flood-prone areas. For instance, codes often require structures to be elevated above the predicted flood level, perhaps on piers or extended foundation walls. Floodproofing involves modifying existing structures through measures like installing deployable barriers at entry points or sealing walls to prevent water from entering during smaller flood events.
Property acquisition and relocation programs represent the most definitive form of nonstructural control, where structures and land are purchased by the government and permanently removed from the floodplain. The vacated land is often converted to open space, such as a park or wetland, which can naturally absorb floodwaters. Advanced flood forecasting and early warning systems also play a significant role, providing communities with crucial time to evacuate people and move property before the water arrives.
The Difference from Physical Infrastructure
Nonstructural measures are distinctly different from the traditional physical, or “structural,” approach to flood control. Structural methods involve constructing physical infrastructure intended to contain, divert, or control the movement of floodwaters. Examples include dams, levees, floodwalls, and channelization projects that deepen or straighten river paths.
The key distinction lies in their objective: structural measures attempt to keep the water away from people and property by physically restraining it. Conversely, nonstructural measures operate on the principle of keeping people and property away from the water, or making them less susceptible to damage when the water inevitably arrives. They recognize that no engineered system can guarantee complete protection against all floods. Structural defenses can sometimes create a false sense of security, encouraging development behind them, which can lead to catastrophic consequences if the structure is overtopped or fails.
Focusing on Vulnerability and Risk Reduction
The overarching goal of the nonstructural approach is to achieve long-term flood risk management by directly reducing community vulnerability. Vulnerability refers to the susceptibility of assets and people to harm. Nonstructural actions decrease this susceptibility by physically removing assets from the hazard area or hardening them against damage. By implementing these measures, communities decrease the potential consequences when a flood occurs, which is a direct component of overall risk.
This approach often provides co-benefits that contribute to long-term sustainability and ecological health. For example, preserving or restoring natural floodplains allows them to function as natural sponges, rather than filling them in or walling them off. This preservation maintains important ecosystems, improves water quality, and offers recreational opportunities, while reducing the destructive force of flood events on the built environment.