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226Ra, 238U, 4 K, and 232Th (228Ra) activity concentrations of 61 soil samples distributed surrounding the rare earth element mine (NORM), MH, Lao Cai, Vietnam have been measured by HPGe detector. The activity concentrations of 226Ra, 238U, 4 K, and 232Th (228Ra) range from 1179 to 6291 Bq/kg, from 1024 to 8351 Bq/kg, from 260 to 3519 Bq/kg, and from 1476 to 35546 Bq/kg in the ore body and from 21.3 to 964 Bq/kg, from 23.4 to 1635 Bq/kg, from 124 to 3788 Bq/kg, and from 40.9 to 6107 Bq/kg outside the ore body in respective. The study area is considered as the high local natural background radiation with the concentration of 226Ra, 238U, 4 K, and 232Th (228Ra) of 156, 254, 647, and 908 Bq/kg in respective. Regarding the spatial distribution, the measured radionuclide concentrations are independent of the distance from measured points to the ore body. With regard to the hazard indices, the average calculated radiological hazard indices, including absorbed gamma dose rate, effective dose equivalent, and excess lifetime cancer risk significantly exceed the global average values. There is a disequilibrium between 238U/226Ra concentrations in studied soil samples. The results also found that the 232Th (228Ra) concentration and total absorbed gamma dose rate show a strong positive correlation (coefficient of determination, R2 = 1).

A model for nonlinear near-bed orbital velocity in shallow water was developed. The equations proposed by Isobe and Horikawa (1982) to calculate the near-bed peak onshore and offshore orbital velocities in the nearshore were modified in order to achieve more accurate predictions. Based on field data from Egmond Beach in the Netherlands, the correction coefficient and maximum skewness were determined as functions of the Ursell number. The model was validated against several different data sets collected during small-scale laboratory experiments at Delft University of Technology, large-s cale laboratory experiments in the Delta flume of Delft Hydraulics, and field campaigns at Egmond beach. The validation showed that the model reproduced well the measurements from both the laboratory and the field.

A numerical model was developed of beach morphological evolution in the vicinity of coastal structures. The model includes five sub-models for random wave transformation, surface roller development, nearshore wave-induced currents, sediment transport, and morphological evolution. The model was validated using high-quality data sets obtained during experiments with a T-head groin and a detached breakwater in the basin of the Large-scale Sediment Transport Facility at the Coastal and Hydraulics Laboratory in Vicksburg, Miss, USA. The simulations showed that the model reproduced well the wave conditions, wave-induced currents, and beach morphological evolution in the vicinity of coastal structures. Both salient and tombolo formation behind a T-head groin and a detached breakwater were simulated with good agreement compared to the measurements. (C) 2011 Elsevier B.V. All rights reserved.