Sunday, 23 May 2010

The Vistula's course over the years

Eddie pointed it out to me on the map of Warsaw from 1831 in my study (below). "Look at how the Vistula used to flow," he said. So I photographed it so that we could compare the 179 year-old map with a current satellite photo from Google Earth (bottom). Both maps are aligned with north to the right.

Warsaw's flood defence systems were built between 1906 and 1912 (za cara - 'in Tsarist times'). As you can see, the river has been straightened out and civilised, its banks raised and land reclaimed. The escarpment, which is closest to the river by the Old Town, has been Warsaw's natural flood defence, being some 30 metres above the mean river level. I've sized the old map as large as possible, so you can click on it to see the detail. It was published in London by Baldwin & Craddock under the Superintendence of the Society for the Diffusion of Useful Knowledge, and dated November 1st, 1831.

All day long, we were following the latest news about the water levels. The flood walls are high enough to withstand 8 metres of water. At midday, the river rose to 7.8 metres. By 23:00 this evening, it had receded to 7.65m. The problem is not now the danger of the river spilling over the walls, it is of the water seeping through. The ground (as I mentioned on Tuesday) is waterlogged, the pressure of the high river is pushing water by osmosis through the soil out on the other side. Fingers crossed for dry weather.


Steve said...

I think the 1831 map underestimates the changes: it was probably made in a dry period. Other maps from around this period show the high points in the surrounding marshy areas as islands.

PolishMeKnob said...

Wow, that's incredible.