(View Point: 46.084428°, -118.909529°)

Wallula Gap is a natural water gap of the through the , and an extremely important Ice Age floods feature along the floods route. This spectacular Columbia River canyon was designated by the in 1980 as a National Natural Landmark.

Wallula Gap All flood waters that crossed the were funneled through this narrow 2 mile-wide gap. The floods were so large that water backed up behind this constriction, rising up to 1,250 feet above sea level and forming an enormous, temporary lake (). The peak flow of flood water through this constriction has been estimated at 10 million cubic meters per second (353 million cubic feet per second); ten times the combined flow of all the rivers in the world.

The floods only exodus from the Pasco Basin to the Pacific Ocean, was through this extremely narrow opening. During the largest Ice Age floods, almost twice as much water entered the 2-mile-wide Gap than could pass through. As a result flood waters backed up behind this bottleneck forming temporary Lake Lewis, which would have drowned the Tri-Cities under 800 feet of water. Lake Lewis may have lasted up to three weeks - the amount of time it would take for all the water to drain through the gap. Wallula Gap Trail (Trailhead Location: 46.061340°, -118.952352°) An ice-rafted erratic is located high above the west side of Wallula Gap. This misplaced, granitic boulder melted out long ago from an iceberg carried by the Ice Age floods.