46
T.N. Burt· I.e. Cruickshank· M.A. Littlewood
Fig. 5.3 Algae blooms which have developed since construction of the Wandsbeck Barrage, on the north
east coast of the UK. (Courtesy ofHR Wallingford)
aries there may also be a change to gravitational circulation which may either compensate for the reduction in tidal flushing or further reduce flushing. Any significant reduction in flushing will tend to make the system more sensitive to pollutant loadings.
5.4.7
Waves
In many barrage situations waves will not present a problem and probably the only
provision necessary will be protection against bank erosion. It should not be overlooked
that some barrages, by impounding large tracts of water at high water level, create a
fetch which could give rise to significant wave effects when the wind direction coincides with the old river alignment. In more exposed situations waves can be a significant factor. For example, in the case of the "Delta" surge barrier on the Dutch coast the
structure is exposed to the direct attack of waves generated in the North Sea which has
had to be taken into account in the design. At Cardiff it has been necessary to provide a
harbour refuge to shelter small boats during storms, whilst they are waiting to enter the
bay through the barrage locks. During construction wave erosion of temporary bunds
was an issue.
5.4.8
Navigation
A fully tidal excluding barrage will prevent movement of vessels unless some form of
lock or removable gate is provided. A part tide-excluding barrage or tidal surge bar-
T.N. Burt· I.e. Cruickshank· M.A. Littlewood
Fig. 5.3 Algae blooms which have developed since construction of the Wandsbeck Barrage, on the north
east coast of the UK. (Courtesy ofHR Wallingford)
aries there may also be a change to gravitational circulation which may either compensate for the reduction in tidal flushing or further reduce flushing. Any significant reduction in flushing will tend to make the system more sensitive to pollutant loadings.
5.4.7
Waves
In many barrage situations waves will not present a problem and probably the only
provision necessary will be protection against bank erosion. It should not be overlooked
that some barrages, by impounding large tracts of water at high water level, create a
fetch which could give rise to significant wave effects when the wind direction coincides with the old river alignment. In more exposed situations waves can be a significant factor. For example, in the case of the "Delta" surge barrier on the Dutch coast the
structure is exposed to the direct attack of waves generated in the North Sea which has
had to be taken into account in the design. At Cardiff it has been necessary to provide a
harbour refuge to shelter small boats during storms, whilst they are waiting to enter the
bay through the barrage locks. During construction wave erosion of temporary bunds
was an issue.
5.4.8
Navigation
A fully tidal excluding barrage will prevent movement of vessels unless some form of
lock or removable gate is provided. A part tide-excluding barrage or tidal surge bar-