Quick after thought, I never heard of the 10 mile rule.
We looked at homes in the Pensacola area that were probably no more than one mile, two at the most, from the Gulf. But they were located on one of the few hills in the area. So at a grand elevation of 27 feet above sea level they required no flood insurance.
If you build to the proper flood zone level either by bringing in fill dirt, or building a stem wall, then flood insurance should only run about $500 a year, regardless of how close or far you are from the water.
Now velocity zones are a different matter.