Modelling of tidal barrier schemes: An analysis of the open-boundary problem by reference to AC circuit theory

In modelling a tidal barrier scheme it is generally difficult to determine whether the downstream boundary is sufficiently seaward to ensure that the prescribed boundary conditions, pertaining to the existing system, remain valid after the barrier has been installed. This problem is examined using the hydrodynamic analogy with AC circuit theory; the essential elements of this theory are summarized.

The first application of this theory concerns the effect of tidal barriers in the River Thames; it is shown that barriers in the region between North Woolwich and Chelsea Bridge will lead to a small increase in the M₂ tidal range. Using a number of models with the downstream boundary successively further downstream, the different results are analysed in a manner which provides an indication of the validity of the tidal prognostication for any particular boundary location.

The second application concerns the Bristol Channel where it is shown that barriers downstream of Newport will produce a small reduction in the M₂ tidal range. In view of the present interest in this region this is an important result confirming the earlier findings of Heaps (1968).