Velocity variations in salt marsh creeks, Jiangsu, China

Velocity variations in a tidal cycle were measured in four salt marsh creeks on the Jiangsu coast, eastern China. Results of regressional analysis show that a marked linear relationship is present between the tidal current velocity and the rate of water level changes. Further, two or three significant velocity surges exist in a tidal cycle. A theoretical analysis indicates that one of the regressional coefficients of the linear equations represents the effect of a component of progressive tidal waves (the tidal waves over the study area are not purely standing waves) and the other coefficient is affected by the geomorphology (i.e. bed slope) of the creeks and the marsh surface. The observed tidal current velocity surges can be related to a rapid water level change (as observed during the initial stage of the flood within a creek) or the combined effects of water level changes and bed morphology (as observed at the end of the flood or during the ebb). Towards the end of the ebb, the surges may be influenced also by the ground water which flows from the marsh surface into the creeks. The established linear relationships may be utilised to develop new techniques to calculate current velocities in the creeks using remote sensing images.