A Serious Warning, Flooding.

Northern Ireland’s First Minister had Question Time. Firstly the questions had to be submitted days in advance, and answering the question was less important than unrelated views and policies. This meeting coincided with a deluge providing the worst flooding we have seen in Northern Ireland for a considerable time. The Minister for Development made a statement as to why the conditions were as bad as they were. It was clear that he had not done his homework as he constantly referred to The Water Service as the Water Company. One would have expected better, as the Water Service replaced the Company in 1973.

A VERY SERIOUS WARNING TO THE UK. Aspects of Drainage the Populace should know. This is a UK matter, not one confined purely to Northern Ireland.
Flooding was inevitable through the demand to increase housing, and the fact that gardens and driveways have been paved over. We should not be surprised, if the outcome is flooding, – although everybody seems surprised.

I have no wish to be boring, so I will try to explain simply how this has come about, and how those responsible for maintaining the drainage, had not and have not a hope in hell of keeping up with progress. To demonstrate the problems the drainage engineers have to face I will use the analogy of the tree. Consider the trunk of a tree, the branches and twigs, starting small and year on year growing taller, the trunk gets thicker and so do the branches as they extend. The drainage of a city started when it was possibly a small village and while the configuration of the pipes of the sewer is like a tree, as time progresses with the city getting bigger the sewers have to be relaid or duplicated; this creates drainage problems, disruption, inconvenience and controversy. House extensions, including conservatories have aggravated the conditions. It is therefore obvious that some trunk sewers will inevitably lag behind the progress of the city. This is a prescription for flooding.

In Victorian times surface water and sewerage were combined, and constructions called storm overflows were later inserted, so that in heavy rainfall the surplus water overflowed into a storm drain and ultimately into the rivers or sea. Unfortunately some of those systems are still in place or being got rid of as fast as possible, but much of the old housing built before the 60s is probably still on a combined system. Engineers designing drainage used to use parameters based upon decades of experience and records, designing in the past for a storm arriving once in a century. Rain falling on hard surfaces has a very fast run off, the rate determined by the gradients. Rain falling on cultivated areas is first of all absorbed and then with saturation, run-off is slow due to the nature of the ground and what is growing there. This is what the minister should have been explaining, especially that no one could have anticipated the rate of rainfall experienced.

Some years ago there was severe flooding in the south of England caused by heavy rainfall and the failure of river revetments. This was not an isolated case and caused me to examine the possibility of designing attachments to the access doors of properties that could be quickly erected by even the most infirm, to hold out the floodwaters. This was possible, however, it didn’t prevent water and sewerage backing up into the house through the toilets and the ventilators.

Water does not flow uphill, but it can be driven uphill by pumps. Totally improving the drainage system of the whole country in areas likely to flooding from downpours similar to those encountered this June, 2007, will never be eradicated using simple drainage methods, it is too vast a problem, especially with global warming, and also rising tidal levels. Pumping in low-lying areas may be the only solution. One of the problems presented with this solution is the plethora of underground piping, cabling, and culverts, that will make this work both difficult and very expensive.

It is therefore possible to appreciate not only the problems to be faced, the urgency of viable solutions, the vastness of the problem, but the timescale and the incredible costs for remedies. The latest intensity of flooding shows that new areas are now vulnerable. I believe the solution lies in segregating areas so that the aggregation of run-off is reduced, with the excess water from these areas being pumped when the rate of flow requires it, to other secure systems of trunk sewers and storm drains. Floodplain problems require different solutions.

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