One bit of warning. I hired such an expert years ago and
although he was fairly knowledgable, his advice was fairly
useless to me. I've got a suburban home, in a nice neighborhood,
with a well manicured lawn on which the children play soccer,
volleyball, football, etc, etc.

My expert suggested a major regrading of the lawn, creating
swales in the middle of the back yard, installing large catch
basins in the swales, and tying the catch basins to an underground
drainage system. I'm certain that his design would work and
greatly reduce the problems that I had, but it was competely
unacceptable to me. He really didn't want to discuss anything
which didn't include the heavy regrading and swales. (He just
advises, he doesn't perform the work). What he suggested would
have looked very out of character in our neighborhood and would
have destroyed the appearance of the yard which I've worked
very hard to achieve.

Just a warning.