JACKSON -- U.S. Sen. Craig Thomas introduced legislation Thursday that would include 443 miles of rivers and streams in northwest Wyoming in the national "wild and scenic" river system.

The national designation in the bill would mean any development must preserve the river's "free flow," and structures including dams and other "large diversions" could not be built. But other uses such as rafting and fishing would still be allowed.

The rivers eyed for inclusion in the system include portions of the Snake River from Hoback Junction to the Idaho border, the Gros Ventre River, the Hoback River, and areas of the Pacific and Buffalo Fork rivers outside Moran.

In total, the bill targets 21 segments along 14 rivers and streams in the Jackson area. About 96 percent of the river miles flow across public lands.

Thomas said the distinction would help protect the "unrivaled recreational opportunities" along the rivers, and help boost tourism.

"As we seek to improve destination travel in Wyoming, it's important to let folks know about the remarkable rivers our state has to offer," said Thomas, R-Wyo. "My bill will designate the Snake River headwaters and certain tributaries as among the cleanest and most free-flowing rivers our nation has to offer. I really see this as a badge of honor for our rivers. I know Wyoming will continue to gain from this distinction."

The only federally designated "wild and scenic" river in Wyoming is a 20-mile section of the Clarks Fork of the Yellowstone in Park County.