Significance of Location in Computing Flood Damage

Expected annual flood damage for individual residential structures may be estimated using generalized depth‐damage and elevation‐frequency relationships developed by the Federal Insurance Administration (FIA). Damage computation using these data for different locations of the structure in the flood plain show a significant difference between structures located within the 25 yr flood plain and structures located outside. Within the 25 yr flood plain, especially within the 15 yr flood plain, damage for one and two‐story structures with and without basements are exceedingly high: up to ten times greater than those outside. Outside the 25 yr flood plain, expected annual damage decreases gradually with location. These observations have important implications for flood plain management. First, economic feasibility of flood control projects will normally require that a significant number of structures be located within the 25 yr flood plain. Second, removal of structures with high damage potential has the secondary effect of reducing economic feasibility of potential flood control projects. Third, outside the 25 yr flood plain, expected annual damage is relatively insensitive to variations in location, depth‐damage function and frequency. Lastly, estimates of expected annual damage using generalized FIA data is useful in preliminary estimates of the damage reduced.