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GUIDE TO FLOOD INSURANCE RATE MAPS 29 below the BFE, the building is within the SFHA. In this example, the FIRM for Sampleville shows a floodway for Little Creek. As shown in Figure 13, neither the property nor the building is within the flood way. S\\\\O\O\ 1"'- ~ c ZONE AE ~ Figu re 13 Step 5, Determine the BFE at the Property To determine the BFE, start by finding the BFE lines (the numbered wavy lines) shown near the property on the FIRM. As shown in Figure 14, BFE lines 108 and 109 are near the property, and 109 is the nearer of the two. When a property is between two BFE lines, such as in Figure 14, you can determine the BFE at the property by interpolating between the two BFEs that are shown. To interpolate, you assume the rate at which the BFE changes from 108 to //0 109 is constant. Therefore, for example, at the point halfway between 108 and 109, the BFE would be 108.5. In Figure 14, the property is approximately six- tenths the distance from 108 to 109; therefore, the BFE at the property would be approximately 108.6. The same principle applies regardless of whether the difference between the two known BFEs is one foot, as shown, or more than one foot. For riverine flooding sources, such as Little Creek in the example, you can also determine the BFE from the Flood Profiles in the FIS report. //0 1"'- ~ c: ZONE AE ~ Figure 14 The example illustia~ed in Figure 14 is a riverine floodplain. In lacustrine (lake) and coastal floodplains, the wavy BFE line is not used. Instead, the SFHA is divided into areas within which the BFE is uniform. Each area is idenlified with a