In the paper, the primarily results of the above mentioned simulations (as waves, currents, sediments transports and bottom - coastal lines evolution) has been shown. Based on the obtained results, there is a strong correlation between the protrusion magnitude and the southward moving of the erosion areas. | Vietnam Journal of Mechanics, VAST, , (2007), pp. 415 - 426 Special Issue Dedicated to the Memory of Prof. Nguyen Van Dao PRELIMIN ARY RESULTS OF THE STUDY ON THE REASO N S OF THE HAI HAU EROSION PHENOMENON I PHAM VAN NINH 1, PHAN NGOC VINH, NGUYEN MANH HUNG, DINH VAN MANH Institute of Mechanics, VAST Abstract. Overall the evolution process of the Red Jliver Delta based on the maps and historical data resulted in a fact that before the 20ll' century all the Nam Dinh coast line was attributed to accumulation. Then started the erosion process at Xuan Thuy district and from the period of 1935 - 1965 the most severe erosion was contributed in the stretch from Ha Lan to Hai Trieu, 1965 - 1990 in llai Chinh -- llai Hoa, 1990 - 2005 in the m iddle part of Hai Chinh - Hai Thinh (Ilai Hau district). The adjoining stretches were suffered from not severe erosion. At the same time, the Ba Lat mouth is advanced to the sea and to the North and South direction by the time with a very high rate. The first task of the mathematical modeling of coastal line evolution of l lai lJau is to evaluate this important historical marked periods e. g. to model the coastal line at the periods before 1900, 1935 - 1965; 1965 -- 1990; 1990 - 2005. The tasks is very complicated and time and working labors consuming. In the paper, the primari ly results of the above mentioned simulations (as waves, currents, sediments transports and bottom - coastal lines evolution) has been shown. Based on the obtained results, there is a strong correlation between the protrusion magnitude and the southward moving of the erosion areas. 1. COASTLINE EROSION AT HAI HAU BEACH The length of the erosion stretch at Hai Hau district ranks the second after the Ganl1 Hao stretch which is located in Ca Mau province, north east of Ca Mau cnp. The 30 km of Hai Hau beach has suffered from erosion at least from the beginning of the last century. The coast has been eroded at a rate of 10 -- 15 m/year during the .
