Philadelphia, Pennsylvania Flood Zones

Philadelphia faces multiple inland flood threats, including riverine flooding from nearby waterways and flash flooding from intense rainfall overwhelming urban drainage systems. Properties near river corridors face the highest risk, but stormwater backup can affect neighborhoods well outside the mapped floodplain. The most common FEMA flood zone designations in Philadelphia are Zone AE, Zone AO, Zone X. FEMA's National Risk Index estimates the county's annual expected loss from inland flooding at over $266.1M. Philadelphia has Zone AO areas subject to sheet-flow flooding, where shallow water spreads across broad, flat terrain rather than channeling through waterways.

With both riverine and urban stormwater flood risk, insurance costs in Philadelphia depend heavily on a property's elevation relative to nearby waterways and the local drainage infrastructure. FEMA's Risk Rating 2.0 prices in multiple inland flood sources rather than relying on the flood zone line alone. If your property is in a Special Flood Hazard Area (SFHA) and you have a federally regulated or government-backed mortgage, federal law generally requires your lender to ensure you carry flood insurance.

Flood zone boundaries in Philadelphia can shift when FEMA updates its Flood Insurance Studies or when upstream development changes how water moves through the watershed. New stormwater infrastructure or dam modifications can also trigger map revisions. Use our free lookup tool to check the current flood zone for any Philadelphia address.