Otter Brook Dam in Keene, N.H., is part of a network of flood control dams on tributaries of the Connecticut River. Otter Brook Dam not only prevents flooding along the mainstem of the Connecticut River, but it also works in conjunction with Surry Mountain Dam in Surry, New Hampshire, to protect the city of Keene, and downstream areas along the Ashuelot River. Completed in 1958 at a cost of $4.4 million, Otter Brook Dam has a storage capacity of about 6 billion gallons of water.