lassig, I was looking at similar plan. Plant 25-30 ft away and start with a red maple, blue spruce, and then a red maple all spaced at 30ft apart. The second row would be spaced 20ft back and would have tulip trees spaced 40ft apart or something similar. I am looking for fast growing. On the other side I would plant some existing black locust (non thorny)and mix in some yellow maples. I wouldn't plant any trees close to the dam/spillway. Then I might mix in some other evergreens to provide some color in the winter.
Another thought was to add some redbud or similar smaller trees later as they need some shade to do well.
