The coastline of Tra Vinh, about 65 km long from the mouth of Cung Hau to Dinh An, is composed of loose sediment, which is easily affected by natural factors and human activities. Based on satellite image analysis combined with survey and field measurements, the changes in coastline between 1966 and 2014 were identified. The results show that in this period the coastline had an average deposition rate of about 5–10 m/year. Dong Hai was the strongest deposition area with maximum rate of 40 m/year, average 28–30 m/year. The eroded coastline alternated with an average erosion rate of about 5–8 m/year. From 1990 up to now, many human constructions have been carried out along the coast of Tra Vinh, contributing to the impact of changing the shoreline. In the area of My Long Nam, Dong Hai and Long Vinh, the mangrove planting project was performed which helped to create continuous accretion of coastline with average rate of 17–33 m/year. In the period of 2009–2014, sea dykes in Hiep Thanh commune and Con Truong, Truong Long Hoa commune were built to prevent coastal erosion. During 2009–2014, Hiep Thanh coast and Truong Long Hoa coast were eroded at an average rate of 8–20 m/year and 6–10 m/year, respectively. After appearance of the dykes, the survey results show that in the 2014–2015 period, the shoreline of Hiep Thanh and Con Trung which has sea dykes was no longer eroded, but the adjacent coastline was more eroded at an average rate of 14–38 m/year. In Dan Thanh commune, where Duyen Hai electric center and Quan Chanh Bo canal were constructed, from 2009 to 2014, the coastline was eroded with the average rate of 12–24 m/year. In 2014–2015 period, coastal erosion was stronger at an average rate of 36–45 m/year.

This paper presents the probabilistic seismic hazard assessment (PSHA) results for Da Nang city. A regional earthquake catalog was updated until 2021 and comprehensive seismic source zones within 150 km of Da Nang city were used. The PSHA results for Da Nang city are presented in the form of probabilistic seismic hazard maps, depicting peak horizontal ground acceleration (PGA) with 10%, 5%, 2% and 0,5% probability of exceedance in 50 years, corresponding to return times of 475; 975; 2,475 and 9,975 years, respectively, as well as the 5-hertz (0.2 s period) and 1-hertz (1.0 s period) spectral accelerations (SA) maps with 5-percent damping on a uniform firm rock site condition, with 2% probability of exceedance in 50 years, corresponding to a 2,475 year return period. The results show that, for the whole territory of Da Nang city, for all four return periods, the predicted PGA values correspond to the intensity of VI to VIII degrees according to the MSK-64 scales. As for the SA maps, for the 2,475-year return period, the predicted SA values at 1.0 s period correspond to the intensity of VI, while the predicted SA values at 0.2 s period correspond to the intensity of VIII to IX according to the MSK-64 scales. These probabilistic seismic hazard maps present short-and long-term forecasts of seismic hazards for Danang city.

No abstract

The Eastern coastal area of the Mekong River Delta has distinctly ecological zones and a potentiality for development of agriculture, forestry and fishery according to their ecological characteristics. The farmer life is mainly depending on exploiting agriculture, aquaculture and there are many supporting the development of social-economics in delta. However, the recent years, farming rice, vegetables, crops, fruit trees and raising shrimp, hard clam as well have heavily affected by drought and salt intrusion due to climate change. This has leaded to decrease the agricultural, fishery yield and the farmer's income, therefore, the farmer's life in the Eastern coastal area faces to the difficulties. The previous farming models are necessary to alter and this is a significant solution to minimize the risk and to cope the climate change such as farming system changes, to sustain agricultural production or transformation to alternative systems and combination between the rotational rice-shrimp-crops farming models following the season. Thus, the study proposes the farming models that can be suitable for the Eastern coastal locals of Mekong river delta. On the basis of document synthesis of natural characteristics, morpho-sedimentology, soil, vegatation cover, innundation, salinity, tidal water level indicating ecology and traditional farming, the study has given a general ecological model for the Eastern coastal area (Mekong Delta) to adapt to the climate change context. The general farming model including five models are clam farming, mangrove forest-shrimp farming, vegetables and fruit trees farming, rotational farming of rice, and rice-vegetables, and Rotation farming rice-shrimp, fruit-shrimp and fishes.

No abstract