MORE WATERY MATTERS
We are all allowed to be wise before the event. Six months ago I ended an article on watercourses in the town with a piece of advice. I recommended that we look to our watercourses and drains before we had an event like the 1932 flood. Looking at the pictures of the flooding on Gisburn Road last week triggered some alarms off for me.
Four weeks ago I sat on the font porch of a house in Minnesota and watched six inches of rain fall inside three hours. Local residents agreed that it was the worst storm they had ever seen and I had news this week that they have had another heavy storm and in the first half of the year they have had twenty two inches of rain, the average for the area is twenty eight inches annually.
I don’t want to get into the minefield of global warning, I’m not competent to give any opinion on it. What I do want to say is that both here and abroad I have seen more exceptional weather events in the last five years than in the whole of my life and I firmly believe that this is the immediate threat.
The flood of 1932 was caused by a cloudburst on Weets Moor. An exceptional event, the sort of storm that the drainage authorities would characterise as a ‘fifty year event’, in other words, an unforeseeable event which could be expected on average every fifty years. The rain on the 24th August was not as serious as the 1932 event but was heavy enough locally to cause problems.
The question that arises is why did this happen? There are three factors that govern this: The amount of rain and the time in which it falls, an inch of rain in a day is no problem, an inch in half an hour is serious. Second, the speed at which the water runs off the ground it falls on, if it falls on a spongy mass like the moor it is absorbed and runs off gradually, if it falls on ground already soaked or impervious surfaces like roads, concrete yards and tarmac car parks it has to run off immediately. The third factor is the size and condition of the watercourses and drains which carry the water away to a lower level.
It’s a long time since I rode a bike but I can remember that one of the great joys of cycling was that if you were going downhill you could freewheel! If you were riding a bike down Gisburn road and stopped pedalling at Hen House Farm you could freewheel all the way down to the bridge beyond Bank Hill. True, there would be a small dip at Foster’s Arms but overall, it’s downhill all the way. Water does exactly the same thing. Give it a clear path to follow and it will run downhill but it’s obvious that on Saturday it couldn’t do that and so it looked for other ways out. My friend’s garden on Westfield Avenue was a pond on Saturday, this was one of the routes that the water took to get to a lower level.
What can be done about it? We can’t stop the rain falling and the whole question of development and the increase in impervious surfaces is a long term planning matter. The route of improvement that is open to us is to agitate to ensure that the watercourses and drains are adequate to carry a ‘fifty year’ event. This is not rocket science.
Nine years ago when I came back to Barlick from my wanderings I took the trouble to raise my concerns with Pendle Council. I was particularly worried about Gillian’s Beck because of my experience with what it could do when I was engineer at Bancroft. I made the point that the culvert which replaces the dam is not big enough to take the amount of water that can come down there in exceptional conditions. Another choke point on Gillians is the culvert underneath Walmsgate. On Calf Hall Beck there is another culvert under Butts Mill which could be a problem.
I’m not suggesting that these three culverts are badly maintained or even inadequate, what I am flagging up is that any exceptional event which is heavy enough to bring debris down with the water can quickly block these culverts and what we should be looking at is the maintenance of adequate safe alternative routes for the water should this happen.
Barlick is lucky, it is high on the watershed between the west-flowing streams of Lancashire and the east-flowing streams of Yorkshire. We don’t have an enormous area discharging its water through the town. Any problems we have will be caused by our own lack of foresight. We need sensible long term public expenditure on our drainage.
All right, you live on top of a hill in Barlick so what’s all this got to do with you? Ever heard of post codes as a means of determining insurance premiums? Don’t think for one minute that the computers at the insurance companies aren’t clocking up the incidence of claims for flood damage and adjusting premiums to take account of this. The computer doesn’t know whether you live in a hole or on a hill, it simply does the sums and applies the results in the easiest way, by postcode. I have friends in Monmouth whose house is house value has fallen even though they have never been flooded simply because their insurance has increased. Could it happen in Barlick?
My picture this week is of excess water running over the fields into Bancroft dam in 1977. The brick culvert under the field, which is still in use, couldn’t cope with the flow so it ran over the top. This wasn’t exceptional weather, just a very rainy day on soaked ground. Use your imagination as to what it would be like if there was a cloudburst. 813527 will always find me, thanks for your comments and advice.
SCG/30 August 2002