09-15-2022, 10:19 PM
(This post was last modified: 09-15-2022, 10:34 PM by MonsGraupius.)
(09-15-2022, 06:17 PM)dadlamassu Wrote: Oddly enough I have waded across the Tay within the last 30 years (so MonsGraupius is exaggerating) and on other occasions when I was younger. Now in my advanced years and with military related health issues it is out of the question so thanks for the offer but I am afraid I need to decline.
Can I ask where? I'm was referring to the lowest ford at Bertha Roman fort (about a mile above Perth). I think the last people on record as crossing at the ford was Crawford (1949:60-61).
When I crossed the ford was 140m across, of which ~100m was running water, the maximum water speed was 1.5m/s and the maximum depth 0.6m and it took 7 minutes to cross at an average speed of 0.34m/s. However, my average speed in the worst 50m, was only 0.2m/s. That is because in this section you cannot walk as normal, because the upstream leg will be dragged downstream below the downstream one causing you to fall. That is because at that water speed and depth, at each step the water grabs your feet and moves it downstream. So, you have to step upstream of where you want your foot to end up. As such, you have to move sidewards like a crab. However, as you lean quite steeply into the flow to counter the water force downstream, you exert a considerable force downstream on the rocks on the river bottom. In the fastest sections, that force is enough to start them moving downstream, so that your footing starts to disappear. Loosing your footing, is a little unnerving when there is 30m of fast flowing very loud river all around you.
The other fun thing, is that on a wide river ford there are very few points of reference. All the water looks the same and in the middle. With the noise and the difficulty standing, if you keep focus on the river (as you need to to work out where to step), it can become disorientating ... it's a form of sensory depravation. You do need to stop, look at the banks and steady the nerves.
However, if you crossed fords regularly, I'm sure it would be easier. On the other hand, I had a specialist life jacket and equipment tailor made for crossing, and I wasn't wearing heavy armour or carrying a big pack ...and if I fell in, I'm an excellent swimmer the water was warm, and I had a dry change of clothes, and I had assistance waiting on the bank.
The closest experience is climbing a 200m cliff, where you lose touch with the ground, or climbing an icy rock face in the wind when it snows and you cannot see the ground.
To put it in perspective, when I crossed, the flow was about 45cumecs. The average flow of the Thames at Kingston is 66cumecs.
Oh the grand oh Duke Suetonius, he had a Roman legion, he galloped rushed down to (a minor settlement called) Londinium then he galloped rushed back again. Londinium Bridge is falling down, falling down ... HOLD IT ... change of plans, we're leaving the bridge for Boudica and galloping rushing north.
