To the southeast, the valley of the notch is drained by the Lost River, leading to the Pemigewasset River,[2] and ultimately the Merrimack, flowing into the Gulf of Maine.

The northwest half of the notch is drained by Beaver Brook and the Wild Ammonoosuc River,[2] part of the Connecticut River watershed leading to Long Island Sound.

The notch lies between Mount Moosilauke to the southwest and Kinsman Ridge to the northeast.

[2] The Appalachian Trail crosses the height of land in the notch on its route between Moosilauke and Kinsman Ridge.

[4] The Lost River Reservation, a wild gorge filled with enormous boulders, is found in the floor of the notch to the southeast of the height of land.