Louisville is a city in Jefferson County, in the U.S. state of Kentucky. It is located at the Falls of the Ohio River. Louisville is located at . According to the U.S. Census Bureau, Louisville Metro (in 2015 measurements for Jefferson County) has a total area of , of which is land and (4.33%) is covered by water. Topography and geomorphology Although the soils and underlying rocks officially put Louisville in the outer Bluegrass region, the city's landscape is better described as being in a very wide part of the Ohio River flood plain. Louisville's part of the valley is located between two plateaus, the karst plateau of Southern Indiana and the Bluegrass plateau of Kentucky, both with an elevation of around 900 feet. Elevations drop off the Indiana plateau very sharply via the Muldraugh Escarpment, whereas the rise in elevation up to the Bluegrass plateau is more gradual. The flood plain is much longer north to south than it is east to west. For example, within several miles of downtown, the Highlands sitting at 540 feet is out of the thousand-year flood plain, whereas areas 10 miles from downtown such as Fairdale and Okolona (both between seven and 11 miles from the river) have the same elevation as downtown Louisville. Most areas in the east end have an elevation from 600 to 700 feet, which, with the typically eastbound winds, trap in heat and pollutants. Areas along and west of the south fork of Beargrass Creek (and more generally, I-65) are located where the Ohio River once ran, so the land here is very flat and is composed of harder rocks. Prior to urbanization much of this area was composed of wetlands, and early roads through these were made of wooden planks. This history is occasionally still readily evident in street names, for example, the spoke road Poplar Level, whose name describes its original construction on planks of poplar. 3rd Street was formerly called Central Plank Road for the same reason. As an industry, namely Standiford Field airport, moved into the area in the 1950s most creeks through the area were rerouted into ditches to alleviate the area's poor drainage and constant flooding. Areas east of I-65 were generally not in the flood plain and thus are mostly gentle rolling hills composed of soft loess soils, hence the reason roads here (such as Eastern Parkway) are very prone to