Unexpected spreads

By which I mean neither awful sandwich smears nor sprawling midriffs. This afternoon's beach walk confirmed my suspicion that last year's spring floods, which deposited quite a bit of sediments and stuff from the upper reaches of the Don onto our beach, had also brought us a few of the invasive plants which have colonised the sunnier meadows up there. Last month a Giant Hogweed reared up; today I saw Himalayan Balsam (Impatiens glandulifera) which seems almost to have grown overnight. It chokes streams down south, but I am surprised to see it here. It is an attractive menace. Like many Impatiens, it has flowers that develop into exploding seed capsules which allow it to spread very efficiently.

The other unexpected spread was seawater. The tidal range here is the greatest I have ever seen outside the Bay of Fundy, sometimes as much as 5 metres. While it used to be relatively easy to get good tidal information through the internet, the difficulty of producing accurate tidal predictions has made that a kind of information which governments and companies prefer to sell. The open source XTide package only has data for the USA; UK data is sold by the UK Hydrological Office (ukho.gov.uk) though they do offer one week's worth of prediction for free. In reading through the documentation for XTide I learned a little about the extraordinary complexity of tidal movement in any particular place: local topography and regional topography interact in all sorts of ways to create harmonics. Tides do not necessarily ebb and flow in a smooth, regular motion.

Today Hakunica and I were walking back along the beach, following the edge of the ebbing tide when a combination of large waves and surge brought the sea in and up again: where we had been walking on dry sand was suddenly under a half-metre of water again, sending me leaping over the old WWII barricade stones and her, older and less nimble, rather dejectedly sloshing through deep pools between them. For a moment I thought I might have to rescue her again; she's not so happy in waves as she was a year ago. After five minutes it all rushed away. The unpredictable dynamics of wave formation at the mouth of the Don, where the tide writhes against the river's flow, is wonderful to watch but this was the biggest momentary reversal of an ebbing tide on an open beach that I have ever seen.

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