Wahluke Slope is a geographic feature in Grant, Benton and Adams Counties of Eastern Washington. It is a broad, south-facing slope with a grade of about 8%,[1] situated between the Saddle Mountains and the Columbia River's Hanford Reach. It has been described as "basically a 13-mile-wide gravel bar" created by the Glacial Lake Missoula floods at the end of the last ice age about 15,000 years ago.[2] Much of the Slope, part of the Hanford Nuclear Reservation, was added to the Saddle Mountain National Wildlife Refuge in 1999.[3] Much of the remainder is used for viniculture.