Extrapolating Raster Data to fill a target area

Discussion created by JeromeBernard on May 2, 2014
Latest reply on May 9, 2014 by JeromeBernard
Thanks for taking the time to review this post ;]
Running: 10.2 with all extensions

Problem: How to get a raster based on features to cover the floodway zone
We are creating a flood hazard map in the following way:
Take FEMA's flood hazard polygons and create a shapefile of the 100 year floodway zone
Take the address points of residences in the county and clip to that floodway zone
Take contour lines from the city and county and join them, then clip to the floodway zone
Rasterize these contours (topo to raster). This is a digital elevation model of the actual terrain in the floodway zone.
Take FEMA's base flood elevation polylines and rasterize based on elevation (feature to raster). This is a digital elevation model of FEMA's estimates of the elevation of the water surface during a 100 year flood event. *(This is the problem)
Then simply use Multi Values to Points to add the fields for the elevation of the address and the elevation of the water surface during a flood. Create a difference field in the attribute table to be symbolized on the map (the lower the difference between the elevation of the address point and the elevation of the BFE, the greater the flood danger.

The BFE lines when rasterized do not fill the entire floodway zone like the raster based on the contours (because the contours were clipped to the floodway, then rasterized).
The BFE lines are only 1 ft in elevation apart so any data cells between the two lines should be easy to estimate, but in terms of latitude and longitude, they are up to 1/8 mile apart. Simply increasing the cell size leads to unacceptable estimation.
Since we cannot capture all of the addresses in the floodway, this model has limited value.

Is there a way in ArcGIS to extrapolate the rasterized BFE lines to fill the same area as the floodway?
BTW, we already tried extending the BFE lines (before rasterizing) with the extend lines tool but without success since some of the polylines have their axis in the middle of the stream channel and diverge (also, extending the lines before rasterization doesn't help fill the gaps between BFEs that are quite far in distance apart). The BFE's vary in length and distance apart but do not vary in that every BFE is 1 ft in elevation different than the next BFE up or down stream. We simply need to fill in the small amount of gaps in the BFE raster that don't cover the entire floodway area.