强潮动力条件下厦门湾低潮阶地型沙滩剖面变形的模拟研究

Evolution modeling of beach profile with a low tide terrace in strong tide environment in Xiamen Bay

以厦门湾沙滩为研究对象,对强潮动力条件下低潮阶地型沙滩剖面变形进行模拟研究.厦门湾沙滩是一种典型的具有低潮阶地的海湾型沙滩,它具有低波浪能量和大潮差的特征.基于这种类型的沙滩剖面侵蚀和淤积机制提出一个基于过程的一维计算模型,对在通常波浪条件下沙滩中长期的剖面演变进行预测.采用厦门湾观音山沙滩剖面变化的实测数据对模型进行验证,两者具有较好的一致性,其最大相差在0.4 m以内.该一维计算模型能够较好地预测低潮阶地型沙滩剖面侵蚀和淤积的一般趋势和程度.模型计算表明,在波浪和潮汐共同作用下,沙滩滩面斜坡带的上部发生侵蚀,而斜坡带的下部则产生淤积,从而在一段较长的时间内使滩面形态趋于平缓.单是由潮汐引起的剖面泥沙输运虽然很小,但是在潮汐的作用下,破波带沿着沙滩上下变动,从而引起潮差范围内一个较宽区域的剖面侵蚀.

Based on the beach in Xiamen Bay, the evolution modeling of beach profile with a low tide terrace in the strong tide environment is carried out in this paper. Xiamen beach is a typical bayside beach with a low tide terrace, which is characterized by low wave energy and large tidal ranges. This paper presents a simple one-dimensional process-based morphological model for predicting medium-long term beach profile evolution of the bayside beach. The model is verified with beach profile data measured at Xiamen Guanyinshan Beach. The results show a good agreement, which the largest difference were no more than 0.4 m. It indicates that the model is capable of reproducing general trends and magnitudes of beach erosion and deposition. Numerical experiments suggest that a combination of wave and tidal forcing make an erosion of the higher portion of a beach and a deposition of the lower portion of a beach, consequently, flattening a beach profile in a long term. The sediment transport only by tide is minimum, however erosions occur over a wide distance associated with tidal range when tides shift the surf zone up and down along the beach.