The Malad River is a 97-mile long tributary of the Bear River in southeastern Idaho and northern Utah in the western United States. The river flows southward, beginning northwest of Malad City, Idaho, crosses the Idaho-Utah state line just north of Portage, Utah, flows through Tremonton, and empties into the Bear River just south of Bear River …The Malad River is a 97-mile long tributary of the Bear River in southeastern Idaho and northern Utah in the western United States. The river flows southward, beginning northwest of Malad City, Idaho, crosses the Idaho-Utah state line just north of Portage, Utah, flows through Tremonton, and empties into the Bear River just south of Bear River City.