SUMARRY

Evaluation and Forecasting the risk of erosion along the Gianh river

 by using the index method integrating technical and natural conditions

in the riverside  

                                                  Nguyễn Tiến Hải, Vũ Hải Đăng, Nguyễn Văn T́nh, Nguyễn Thái   

 

The Gianh river is one of the big river in the North Central of Viet Nam. In recent years, the riverside of the Gianh River has been eroded with various degrees of length and speed, which results strong impact on the environment and people here. On the basis of the index method integrating technical and natural conditions in the riverside, the risk of the erosion of Gianh River (from Châu Hóa Bridge to Cửa Gianh) can be assessed as follows. The documentation used are mainly the survey data of the authors. In addition, they have inherited the data of the researchers. The risk erosion along the North shore of Gianh river (the length is 69 km): (1) Strongest erosion: about 4.759 m (6.8% of the total length with three sections); (2) Strong erosion: about 17.750 m (25.72% with fifteen sections); (3) Erosion occurs on average: about 11.000 m (15.94% with twelve sections); (4) Small erosion: about 26.000 m (37.68% with thirteen sections) and (5) No erosion: about 9.500 m (13.78% with five sections). The risk erosion along the South shore of Gianh river (the length is 65 km): (1) Strongest erosion: 4.250 m (6.54% of the total length with three sections); (2) Strong erosion: 19.500 m (30% with ten sections); (3) Erosion occurs on average: about 17.500 m (26.92% with thirteen sections); (4) Small erosion: 8.500 m (13.08% with four sections) and (5) No erosion: 15.250 m (23.46% with three sections). The risk erosion along the coast of the four isles (total length about 25.375 m of Tiên Xuân, Cồn Quan, Cồn Ngựa and Quảng Hải, Cồn Sẻ isles): (1) Strongest erosion: 3.500 m (13.79% with two sections); (2) Strong erosion: about 8.000 m (31.53% with six sections); (3) Erosion occurs on average: 4.875 m (19.21% of the total length with six sections); (4) The risk of small erosion is about 7.750 m (30.54% with five sections) and (5) No erosion:  about 1.250 m (4.93% ). The greatest risk of erosion is: Meandering channel from Phúc Tiến (Quảng Tiến) to Tiên Xuân isle and the South shore of Quảng Hải isle. 

Keywords: River bank erosion, Gianh river, technical conditions.