On the Variation of Surface Moisture on Mild-Slope Beach

• Main Authors: Chien-Lun Huang, 黃建綸
• Other Authors: Hua Chien
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/34582125579926273577

碩士 === 國立中央大學 === 水文與海洋科學研究所 === 101 === Previous studies have shown that the wind speed is one of the most dominant controls on aeolian sediment transport. Coastal zone is at the interface among the ocean, atmosphere and the land, where the effects of the moisture content of the top few grain layers (surface moisture) to aeolian sediment transport is even important. This study highlights the dynamic spatial and temporal variability in surface moisture content on mild-slope beach. In this study, the observations were carried out at Yung-An Beach, Xinwu, Taoyuan. Two methods, surface brightness method and gravimetric method, were adopted to measure surface moisture. Furthermore, comparisons of surface brightness content and gravimetric moisture content in an attempt to examine the accuracy and possibility of the surface brightness method was implemented. The results demonstrates that the tidal difference is an important control on aeolian sediment transport in Yung-An Beach. Spring tide is the necessary condition that the surface moisture could be reduced to certain level that its corresponding wind speed thresholds for aeolian transport is less than the ambient wind speed. When the spring tide if the groundwater table is lower than the zero flux plane (ZFP), surface moisture decreases with time in exponential decay. Intensive evaporation due to wind and solar radiation results in faster surface moisture decay and allows the aeolian sand transport. Present study applies data analysis to separate the effects of tide and evaporation on the surface moisture. We proposed a surface moisture content decay formula to assessment the possibility of the occurrence of aeolian sediment transport decay in the mild-solpe beach environments.