If you are keeping water on a wetland for the benefit of wetland wildlife then it occupies some of the volume that could otherwise have been used for flood storage.
This can give rise to the claim that the schemes that benefit wetland wildlife that have exacerbated flood impacts. To some extent this is bound to be true – but to what extent?
Hardly any, according to this summary (of this full report) from the Somerset Levels – remember the Somerset Levels?
‘The assessment finds that the volume of water maintained within ditches, and corresponding reduction in flood storage capacity, represents a very small fraction of the volume of flood water stored on the moors during major flood events. Expressed both as a proportion of the maximum flood volume or change in flood level, the calculations indicate that winter raised water level areas have only a very minor impact on large flood events. Water levels for agriculture in summer occupy larger volumes, but these are still small compared to volumes of water stored on the moors during major flood events.’
In other words, as is so often true when we think about it, we can wildlife with very little trouble at all. That’s nice isn’t it?
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