Re: destruction of trees on private property
I can't really address curbside appeal, but as to the rest of your question, I litigated a tree case up to the Court of Appeals (Monteleone v Floral Park, summarized on my page). The question involved liability for injury from a low hanging tree branch. The tree was planted and owned by the Village, adjacent to a house and sidewalk owned privately. The Village only maintained and trimmed the tree when they received a call.
Essentially, the rule that came from the case is that a municipality will not be liable for injuries from one of their trees unless they are given prior written notice of a defect, similar to the pothole law.
In your situation, if the village is damaging private property (your trees) that need not be damaged to install the pipe, and the engineer advised against it, you may be able to a) recover
from the county for the trees, or have them replaced after the work is complete; and b) with respect to liability, make sure that you provide prior written notice of the acts of cutting and uprooting the trees, and the potential storm danger.
In the event of an accident, while it will not prevent you from being sued, the real negligence will be that of the local municipality if they do not act on your information.
If you would like to discuss this further, call my office for an appointment.