Flooding

Flooding is the temporary inundation of land that is normally dry. It can result from excessive rainfall, rapid snowmelt, coastal storm surge, or the failure of a dam or levee. Flooding may occur gradually as river levels rise or suddenly as flash floods.

Types and causes: River floods occur when rivers carry more water than their banks can contain. Urban flooding happens when heavy rain overwhelms drainage systems. Coastal flooding is driven by storm surge and high tides. Other forms include flash floods, dam-break floods, and ice-jam floods.

Impacts: Flooding can damage homes, infrastructure, crops, and utilities, displace people, and cause injuries or loss of life. Economic disruption, soil erosion, and water contamination are common, and recovery can take years. Vulnerable populations, including low-income communities and those in low-lying deltas, are disproportionately affected.

Prediction and response: Forecasts rely on rain gauges, river gauges, weather radar, and hydraulic models to estimate flood extent and timing. Early warning systems, evacuation plans, and rescue operations reduce risk. Post-disaster relief and recovery programs help communities rebuild.

Mitigation and adaptation: Strategies include land-use planning to avoid development in flood-prone areas, construction of levees and dams, and wetland restoration. In urban areas, green infrastructure, permeable pavements, and rainwater harvesting reduce runoff. Insurance and public education support resilience and preparedness.

Climate change and variability: Changes in precipitation patterns and sea level are expected to increase flood risk in some regions, making adaptation and resilience measures more important for infrastructure and communities.