Lower Boulder Creek about 1/4 mile west of 55th street has a couple strainers in inconvenient spots (between 55th street and the railroad bridge west of it). #1 is a thick tree branch from above that goes under water leaving just enough room for a boater to pass under an inverted 'V'. It's on a very swift left turning channel and nearly impossible to go around. There's a huge floating trash heap on boater's right. Avoid that too.
80 feet downstreem is a narrow, sharp right turning channel with a bush/jam/root/strainer thing.