Floodplains are composed of the floodway - which conveys the water from rain events, and the flood fringe - which conveys the excess overflow from extreme rain events. Modern sustainable practices prohibit the construction of new residential buildings in floodways and put restrictions on the construction of new buildings in the flood fringe. This is why the new Y is elevated.The easternmost portion of 415 (one-third of the total site) along the railroad tracks is in the floodway, where new residential buildings are prohibited, and therefore all of that portion is proposed to be incorporated into the Treeline Trail. The Treeline Trail, formerly called the Allen Creek Greenway, is an urban trail which follows the Allen Creek contour from the UM Athletic Campus to the point where the Allen Creek empties into the Huron River on N. Main Street. It will connect with the county-wide Border-to Border Trail. The rest of the 415 site (two-thirds of the total) is in the flood fringe.