On Fri, Jul 2, 2010 at 12:05 PM, roger_millin <[email protected]> wrote: > > The outside of the bend in question is shown as having rocks and stone heaps. > Your knowledge of the outside of bends being shallow is counter-intuitive as > one is generally taught that the scour (and hence the water depth) will be on > the outside of the bend (due to the higher water velocity around the outside > I guess), but the chart generally confirms what you say with lots of rock > deposits shown. I guess that this *is* due to the higher water velocity as it > has the power to shift the rocks and dump them when the velocity falls off.
I think what happens is that the water hits the outside of the corner almost straight on, and this creates turbulence which keeps the moving water away from the outside. The inside suffers the usual problem, so the deep water is slap bang in the middle of them. You can see the boils on the outside which shows the sudden change in speed. > There is a specially enlarged whole page featuring this Laneham stretch in my > guide, a useful indicator that it requires special attention. This stretch > defies the above suggestion about 'shallow on the outside' as there are rocks > and shallows on both sides and the navigation channel winds its way down the > realatively gentle curve of the river. Actually it was just upstream of Laneham - where because of it's reputation I take care and stay where it's deep. This was a sudden shallowing, more than half way into the river (I was virtually dead centre of the river at this point). Chugging along quite happily one second, then a large wash from the swim in the shallow water before bouncing on the bottom to a stop before I even had time to take it out of gear! The tide was dropping, so I had to get off quickly, thankfully the stern on Victoria was nicely low to stop the prop from ventilating, and pumping out water from balast tanks, and furious movement of coal saved the day! Mike -- Michael Askin http://shoestring_DOT_zapto_DOT_org/
