flow rates and flood risks in small un-gauged drainage systems throughout urban areas can follow a different trend than large river systems in the canadian reference hydrometric basin network database. hydrology in smaller drainage basins is governed by the degree of urbanization and impermeable, high-runoff surfaces. in the don river watershed in the lake ontario basin, urbanization of 15 percent of in 1950 is predicted to become 91 percent in 2021. average annual flows in the don river have increased by 0.44% per year since the early 1960s.