A towhead is a sandbar that has cottonwoods on it as thick as harrow-teeth.

沙洲是片沙土岗子，上面白杨，密象耙齿。

As soon as I got started I took out after the raft, hot and heavy, right down the towhead.

开动，我就顺着沙洲，朝着木筏，拼命追去。