I just talked to a farmer recently about Cottonwood trees and falling limbs.
While out for a ride on Sumas Prairie I came across the largest diameter trunk on a Cottonwood tree I had ever seen. I even put my bike against it and took a pic. The farmer was there and I marveled at it's size and he said "yeah, but I'm gonna cut it down". He said "see all those branches there (there were a lot on the ground). Every year it drops more and I'm sick of picking them up."
I later took my wife for a ride to look at the tree before it is gone.
I'll try to post that pic when I get home from work.