Why is Chingford Plain and other parts of Epping Forest inEssex undulating?

Question

I was told it could be ancient plow marks or it was dug up during the war to stop enemy planes or gliders landing neither sound right to me. Plow lines are closer together usually and posts in the ground would be more effective against aircraft

Answer 1

According to history what you were told is exactly right. In the nineteenth century about 1860 it was ploughed and farmed. The ridges can still be seen on the Golf Course and the eastern part of the Plain. In 1940 deep ditches and piles of soil were formed across the Plain to counter the threat of landings by German gliders.
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Answer 2

Not being from your area and having a different history (North East US), we have areas like that where the ground is like huge water ripples. And they are. Sometimes it is the compression of land as would be shown by laying a blanket out and pushing it together to form waves. But I suspect you might be seeing soil and sand deposits from the retreat of the last glaciers of the ice age past. As the ice moves down it scours the ground and rock and the material mixes with the ice. As it melts, the dirt ice retreats in sections and frequently leaves ridges or material, a lot of times because the dirty melt-water collects on the surface and lets go during the normalizing seasons (warm summer periods). So if the land tends to be sandy with a lot of boulders and rocks scattered about, probably now in long rock walls, and if there is some sand and gravel deposits and businesses mining them, that is the source. Your library will have a collection of your area's natural history.