We love trees. Trees in your yard can help a great deal with slowing down stormwater.
Here is a nifty calculator to estimate the gallons of stormwater runoff a tree in your yard would intercept over a year. This is important for not only helping prevent polluted water from making it to the local streams and rivers but trees also save you money.
We also had a webinar during the summer on The Importance of Trees.
You can listen/watch it
Trees and native plants benefit a community. Their above-ground features - food, shelter, landing places, etc. are important for wildlife and the part we don't see - the roots - are important for holding soil together and soaking up moisture.