Initiative Research On The Transportation Of Suspended Sediments In Jiulongjiang River Estuary,Fujian Province,At Both Flood And Low Water Seasons

The movement of sediments in estuary is a key problem of marine sedimentology. On the basis of former researchers' work and the self on-spot observation(salt, current velocity, particle size, sediment charge), this paper studies the transportation of suspended sediments in Jiulongjiang river estuary, Fujian province, at both flood and low water seasons. With the help of calculation and drawing graph, the paper analyzes the movement of suspended sediments of the estuary in a full way, such as the distribution of suspended sediments, starting velocity of the surface sediments, and especially the stagnant point and sediment discharge. The paper finally draws a conclusion on the source, transportation and deposited area of suspended sediments.The study shows that the average particle size increases from 6.68 Φ to 7. 05Φ from the flood season to the low-water season, and the clay charge increases from 21.4% to 28.3%, yet the sand charge and the silt charge decreases from 6. 3% and 72. 3% to 4. 9% and 66. 8%. It indicates that the clay sediments from the Xiamen outer port could be brought by the flood tide to the estuary. The average particle size of the surface sediments in the estuary is between 6Φ and 7Φ, and the correspondent velocity is 50-80cm/s. While the average velocity of flood and ebb tide is 69cm/s and 84cm/s at flood season and 79cm/s and 87cm/s at low-water season, the silt sediment in the estuary will re-suspend under the tide control.The results show that the runoff of Jiulongjiang river is the main source of suspended sediments, another source is the surface sediments from the estuary, the third source is the clay sediment from the Xiamenouter port. According to the calculation of sediment discharge, the river input 209 OOOtons of suspended sediments everyday to the estuary at flood season, and the Xiamen west port input 5 OOOtons, and Section Hulishan output 8 OOOtons. The daily net input of flood season is 206 000tons. At low-water season, the river input -31 000tons everyday to the estuary, and Xiamen west port input 23 OOOtons, and Section Hulishan output 84 OOOtons. The daily net input is -92 000tons. As a result, it has a net input of about 17.1×106tons to the estuary a year.The suspended sediments are distributed in different areas of the estuary, such as the west of Haimendao islet, the east of Haimendao islet, the south of Gulangyu islet and the Dapanqiantan shoal, where in estimate can deposit respectively 14. 8× 106tons, 1. 38×106tons, 0.9×106tons, and - 18.0×106tons of sediments a year.