Octopus trees in surburban Detroit.

I earned my money today, going from a 6am puddle jumper to Chicago to Detroit and thence to car rental and some 80 mph eight-lane interaction with the singularly aggressive and big car driving Motor City populace before putting on my waders on a street in McMansionland ("Going hunting?" said the yap dog-walking retired condo lady) and busting through a couple of miles of briar patches to lay out transects on this urban stream.

Maybe you know about "telephone pole trees" on depositional floodplains--the basal flair gets buried and they come straight out, like poles. I've worked on this stream (nameless to protect the innocent) for years, but never noticed that there are many trees on part of its floodplain that show an "octopus" form in which material has been eroded from the base. It's not just this single tree--it occurs uniformly over a kilometer or so of linear stream length. The trees seem happy otherwise.

This area has gone from mostly farmland to upscale suburb in the last 15 years. I think a developer scraped the the floodplain, leaving soil around the trees that was later removed by flooding, but I'm open to suggestions. It's a very low slope/energy system, very stable now.