Rice fields in Vietnam (ruộng or cánh đồng in Vietnamese) are the predominant land use in the valley of the Red River and the Mekong Delta. In the Red River Delta of northern Vietnam, control of seasonal riverine floodings is achieved by an extensive network of dykes which over the centuries total some 3000 km. In the Mekong Delta of southern Vietnam, there is an interlacing drainage and irrigation canal system that has become the symbol of this area. It jointly serves as transportation routes, allowing farmers to bring their produce to market. In Northwestern Vietnam, Thai people built their "valley culture" based on the cultivation of glutinous rice planted in upland fields, requiring terracing of the slopes.