El Niño & Flood Resources 

Resources

El Niño Amplifies Compound Coastal Flood Risk · Blog post on The Confluence at CIWR
How El Niño can influence compound coastal flooding through changes in land- and ocean-based processes.

El Niño Community Resource Guide
A one-page guide with links to flood preparedness information.

FAQs

How does El Niño affect coastal flooding?
El Niño changes multiple land- and ocean-based processes at the same time, which increases the risk of flooding along the coast (and inland). The 2026-2027 El Niño is anticipated to be historically strong and record-breaking, favoring increases in seasonal precipitation as well as heavy precipitation across the state. Increases in both seasonal and heavy precipitation can drive widespread fluvial (river) and pluvial (surface) flooding. El Niño is also associated with elevated coastal sea levels. Coastal trapped waves associated with El Niño propagate along the coast, raising sea levels for weeks or longer. At the same time, storms can raise coastal water levels through storm surge and wave action. High tide events that occur alongside these stressors further amplify the risk of coastal flooding.

What are compound coastal flooding events?
When any of land- or ocean-based flood-generating processes combine, compound flooding events can occur, even when individual drivers are not extreme. In fact, in many places, we now know that coastal floods often arise from compounding stressors. High sea levels can reduce rivers' ability to drain to the ocean and increase upstream flooding. Storms that bring heavy rainfall also often raise sea level through storm surges and wave events.

How do I prepare and stay informed for coastal flooding?
For coastal California, preparing means paying attention to conditions on both sides of the shoreline. Watch local flood warnings and coastal hazard advisories. Know whether your home, workplace, or travel is in floodprone areas. Be mindful even if it hasn’t flooded before. 

• Prepare an emergency kit and sign up for local alerts.

• Clear gutters, drains, and other drainage pathways before storms.

• Know where to get sandbags or other flood barriers if your property is at risk.

• Consider flood insurance before winter, especially if you live in an area that floods or drains poorly.