YOUR LETTERS: At some point defences will be over-topped

Eddy Poll
Eddy Poll
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The last time Richard Fairman commented in your pages about how he had reduced the flood risk in our area, I let it pass. But not this time. Because so much of the east coast of Lincolnshire is at or below sea level and on most days of the year there are two high tides, the tidal flood risk is twice a day.

However, as he rightly points out, the generations of great drainage engineers (including the Internal Drainage Boards and the Environment Agency) have provided us with defences that mean that the probability of tidal inundation is relatively low, generally speaking about 1 in 200 in any one year.

As you know, much of our land, including housing, is lower than the embanked 
water courses that drain into the sea. This means that the risk of fluvial flooding is any time the water level is higher than the surrounding land. In a lot of places this is all the time. Again, due to the skills and efforts of the aforementioned generations of engineers, the probability of fluvial flooding is also much lower, around 1 in 100 in any one year.

The problem highlighted by the maps, is that should a breach occur, the water will remain in the low-lying bowl created by the surrounding embanked water courses, such as between the Welland and Coronation Channel, until it can be pumped out. This was the problem on the Somerset Levels.

I have been friends with Richard for over 25 years and am currently helping him repair the engine in his boat. Richard is an engineer and as such maintained his engine well. However, on a trip along the Welland, we were stranded near Peak Hill when the 
engine broke.

Despite his best efforts to prevent it, the engine was put under pressure once too often and failed.

The same is true of flood defences. The probability is, the reality is, that at some point the defences will be overtopped and forces far 
beyond our control will determine the extent, velocity and depth of the ensuing flood.