Apart from Cam river, Ba Che rivers, Tien Yen river, Pho Cu rivers are in plumose shape. Almost all the rivers are shaped like a paper fan opening widely.
The river mouth areas are invaded deeply by salt water. In addition, the botanical layers in valleys have a low coverage rate which results in regular wash-out, then the amount of silt, soil and rock gradually increases whenever appearing huge flood. Thus, many rivers and springs are rapidly filled up, especially in some exploitation areas like Vang Danh spring, Mong Duong river.
Besides the four big rivers, Quang Ninh also has eleven small rivers, with the length between 15 and 35km; the basins whose area is lower than 300 km2 are located along the coast, including Trang Vinh river, Ha Coi river, Dam Ha river, Dong Cai Xuong river, Ha Thanh river, Dong Mo river, Mong Duong river, Dien Vong river, Man, Troi river and Mip river.
All of the rivers and springs in Quang Ninh appear to be short, small and of high grade-level. The features of currents differ between seasons. In winter, most rivers run dry, but in summer, waterfalls pick up fast currents. The water current reaches 1,45 m³/s in dry season, but up to 1,500 m³/s in the rainy season. Quang Ninh’s sea borders upon the Gulf of Tokin. It is large and protected by the ranks of islands, so the wind is quieter and the water smoother. The gulf’s current runs from north to south. It is Vietnam’s coldest sea, with the temperature sometimes dipping below 13 °C./.