关键词: 潮滩, 季节性冲淤循环, 长江三角洲, 因子分析

Abstract: Based on the surveyed data of seven coastal sections (4 in the Changjiang River Estuary and 3 in the Hangzhou Bay) and the collected data of wind, sea level, tide, offshore suspended sediment concentration and river supplied sediment flux from adjacent stations, the paper deals with the regressive correlations between the monthly average flat elevations and monthly average figures of the influential factors. All sections except Xijagang which is located within the river mouth show negative correlations between flat elevation and sea level height and between flat height and tide range, with the correlative coefficients being -0 53～-0 91 (averagely -0 77) under the former condition and -0 56～-0 97 (averagely -0 80) under the latter condition. All of the five sections with available suspended sediment concentration data show positive correlations between flat elevation and sediment concentration, with the correlative coeffitionts being 0 35～0 97 (averagely 0 66). Only two sections (one in the Changjiang River Estuary and the other in the Hangzhou Bay), which have the features of sand in sediment composition (Φ₅₀ <4 0) and slope gradient (> 0%), show negative correlation between flat elevation and shoreward wind frequncy and average wind velocity, with the correlative coefficients being -0 57 and -0 69 (averagely -0 63) and -0 61 and -0 75 (averagely -0 68) respectively as in sand beaches. Other sections do not show uniform relationship between flat elevation and wind conditions. Due to the local marine factors the offshore water sediment concentration has obvious negative correlation with the Changjiang River sediment flux, which results in unrational negative correlation between flat elevation and river sediment flux. The paper also gives sediment dynamic and morphodynamic explanations of the above correlations. Sea level rise results in the spread of wave breaker zone from subtidal area to intertidal area and then increases the intertidal water energy. The larger the tide range, the stronger the tide current and the erosion effects. The larger the flood water sediment concentration, the easier for the sediment to deposit on the flat. In the condition of precipitous slope (as in sand beach) wind driven wave holds more energy when it reaches intertidal flat than in the condition of gentle slops, so wind playe a more important role in the former condition than in the latter condition.

Key words: tidal flat, annually cyclic erosion deposition, the Changjiang River delta, factor analysis