On Tue, Apr 22, 2008 at 8:11 PM, Peter Stockdale <[EMAIL PROTECTED]> wrote: > > --- In [email protected], "Andrew Dyke" <[EMAIL PROTECTED]> wrote: > > Well I have no way of knowing, I was given those figures by the EA > man, who > > Yup - I would think a more accurate figure would have been 20 - 25mph. > Absolute tops. > > In order to get higher figures the gradient on the river would have > had to be of "Rapids" proportions ! > > I have the dubious benefit of having navigated the Avon in flood > conditions. > > "Dont bother with the lock, boys" (D.H. -- 197X)
I always find it amusing when people come up with out of the air figures like this. Water has some sort of magical appearence that always makes it look faster than it really is - would you go at 4mph on a road all day and think it was fast? ...and there-in lies the rub. On a large river while making good process, by using the window frame or a hand, block out all land leaving just the water in view. Now how fast do you think you are going? It seems faster, no? In fact, and I know from experience, a large volume of water travelling at only 4 mph looks like its going a lot faster, and while it takes a long while to get anywhere when you are pushing it (or it's seems like you are flying when going with it) it is pushable by most narrowboats. Of course I can only go by the water flow at Pershore during the main part of the flood, though we saw most of the river at more than 6 inches in the yellow. By my reckoning (and I'll have to check the video) I would say the flow just above the lock (where it narrows for the mill weir stream) was never running at more than 8 mph, and probably a lot less (6 or so mph). In fact as the levels were nearing normal seemed to be when it was flowing at it's fastest pace as the water was channelled into a smaller space. The lock keeper at Pershore told us "horror" stories of how at a up coming big bend in the river the water was flowing at 40 mph, later this dropped to 20 mph, and it must have been obvious to him we know more about water and river than he because he changed the subject very quickly. In fact just below the bend was the fastest flow as the silt washed from the corner settled and caused a shoal. I can't find any useful figures at the moment to calculator water flow rates for a particular height difference to back my claims - there must be some out there?, but don't over estimate the speed of water just as you should never UNDERestimate the POWER of water. Cheers, Mike -- Michael Askin http://shoestring_DOT_zapto_DOT_org/
