Are you interested in maps and GIS but don't have access to ARCMAP? Do you live in Pittsburgh? If so, check out this City of Pittsburgh Maps website. This website allows you to check out some different GIS data layers of the city, including zoning maps, road maps, aerial photos, and even wooded areas. I don't see sewers or historic stream channels on here yet, but there's no reason they can't be added at some point.
One of the most interesting things I noticed while perusing these maps is that almost all of the areas that are forested are also 'landslide danger areas'. This really demonstrates how important trees are in stopping erosion and landslides. It also really illustrates the fact that trees were mostly preserved in areas that were hard to develop. When pondering the nature left in the refugia amongst the city, we should also think about welcoming nature back into flatter areas as well, amongst our homes and businesses, instead of banishing it to our steep slopes.
Anyway, check out the maps, and see what you can discover on your own!