This section includes the Flood Insurance Rate Map (FIRM), prepared and approved by the Federal Emergency Management Agency (FEMA). The Planning Board uses it to designate areas with a 1% probability of flooding occurring or exceeding that in a given year.

In the case of Puerto Rico, the maps show the Special Flood Hazard Areas (SFHA) with the symbols A, AE, V, VE, AO, A99. They also show areas that are outside the SFHA, such as those identified with X.

In the San Juan Bay Estuary watershed, 14.6% of the municipality of Carolina is flood-prone. Meanwhile, in Loíza, flood-prone areas cover 11.7%, followed by San Juan with 10.6%, Cataño with 4.73%, and Guaynabo with 1.46%.

Flood zones are classified by gradation: high, moderate to low and high (coastal zone).

The regulations include provisions for public review, appeals, and corrections to flood risk information that take into account field conditions. As with any analysis of this type, there are variations in flood elevation estimates and flood zone boundaries.