Posted on 27 February 2011 at 13:36h

As the snow melts and the forecast is for more rain the plan to use snow as the theme for our group 4 project seems less and less likely . A back up plan has been hatched so it looks possible that we will be indoors building paper bridges instead. Well at least the bridges will be useful for crossing the roads that are rapidly turning into rivers.
When the rain runs down the road it forms some interesting patterns, if there is too much it basically forms a river but if there is just a few millimetres you get an effect like the one I have tried to photograph in the picture. What you can just about see is a series of wave like features lining up down the road. What seems to be happening is the surface water is travelling faster than the water in contact with the road so overtakes it. This results in a build up of water which "breaks" like waves on a beach. As the waves progress down the road they spread out until the "waves" reach terminal velocity. When I was a teacher at Atlantic College in Wales, one of my students wrote an extended essay about this. I remember he struggled with recreating the waves in the lab and also found it difficult to measure lengths from photos like mine due to the perspective.