HOA flood zone long term planning.

That is complicated and depends on situation. Ours only 2 or 3 homes flooded. We had to get them onto the flood zone so could get flood insurance. The HOA did not qualify for flood zone or insurance for flooding.

We put in a burn and french drain system.

It should be noted that using mulch from fallen trees can spread disease. It is good kept it local. However using other mulch untreated can spread grass and tree diseases.

In some states (like mine) all of this is controlled by a water management district and the Corps of Engineers. We can't just plant what we want - we have to get permit and have studies done. I would be very careful to change what the developer left you without making sure you aren't violating some kind of regulation.

I take it your board spoke to landscaping experts about the best way to use trees and plants to reduce flooding – if not, you should have. Not sure why people would complain it looks different – if you plant 200 trees, how on earth is the area supposed to look after that?

I’d be more concerned about the planting being effective (it’ll take a few years for the trees to reach maturity), so you might want to talk to a landscaping company (one – three, perhaps) to see if there’s something else you can consider. For example, a wildflower meadow can also help with flood control (assuming that's what the 70% were thinking of), but you'll probably want to use native plants.