"Stream simulation" means a method of designing and constructing a stream crossing structure, in which the structure created within the channel is as similar as possible to the natural channel in both physical structure and function, and which takes into account appropriate bed forms and streambed characteristics so that water depths and velocities within the crossing structure at a variety of flows are comparable to those found in the natural channel upstream and downstream of the stream crossing.
N.H. Admin. Code § Env-Wt 902.32