1. A computer-implemented method for predicting a flood elevation for a flood frequency for a property point, comprising: calculating with a processor at least two points of flood frequency versus flood elevation for the property point using a flood map; defining a relationship between flood frequency and flood elevation for the property point using the at least two points; and predicting with the processor at least one flood elevation at a flood frequency different from the flood frequency of one of the at least two points for the property point using the relationship; wherein the flood map comprises a map of flood zones, defined by flood boundaries, and a plurality of pre-existing flood elevation lines; wherein calculating with a processor at least two points of flood frequency versus flood elevation for the property point comprises: geographically aligning the flood map with a digital elevation map; and forming a substantially perpendicular line, on a digital elevation map, between the property point and a flood source line feature of a flood source in a same catchment area as the property point; wherein the at least two points of flood frequency versus flood elevation for the property point are derived from geo-referenced discrete points, on the digital elevation map, for flood frequencies corresponding to a location on the flood source in a flood water surface profile that is on the substantially perpendicular line; and wherein the flood water surface profile provides flood elevation for a flood source at given distances along the flood source; wherein the defined relationship between flood frequency and flood elevation for the property point is a logarithmic relationship; wherein the logarithmic relationship is defined by the equation: 
 Flood elevation=a Log(flood return period)+b where flood return period is 1/flood frequency, and wherein a and b are defined by solving the equation for the at least two calculated points.