This is a big deal with fish passage restoration. Rectangular farmland led to dykes that straitened out streams and rivers. Straight waterways flow faster and

This is a big deal with fish passage restoration. Rectangular farmland led to dykes that straitened out streams and rivers. Straight waterways flow faster and wash away sediment. This makes it harder for fish to swim upstream while leaving fewer places to rest and spawn. There is a fair amount of restoration work going on in the PNW to try and undo this, and the results I've seen have been promising.