Stream Simulation in Altered Riverscapes Sample Clauses

Stream Simulation in Altered Riverscapes. Background Stream simulation culvert designs are often considered in natural channel stream reaches as a means to pass all fish. For example, the consideration of bankfull width, and thus culvert dimensions, is best considered in unaltered reaches which have evolved with basin- specific precipitation and channel dynamics. These reaches are commonly at equilibrium with the forces that shape the channel. However, in highly altered stream systems, stream simulation principles may equally apply. In a permanently altered (artificially constrained) riverscape where channel dynamics up- and down-stream are similar to what would exist inside a new culvert repair/replacement, a stream simulation culvert design may be feasible to construct. The purpose of stream simulation criteria is to mimic natural channel processes inside the culvert such that it resembles and functions as though the culvert itself were not present (or nearly so). Thus, stream simulation designs model upstream and downstream reaches in the culvert designs. In permanently altered and constricted environments, channel dynamics can be equally modelled after upstream and downstream reaches. In essence, the permanently altered environment may have established in-stream equilibrium from which a channel inside the culvert can be designed to mimic. Where certain criteria exist in altered channels, it may be possible to design stream simulation culverts. Under these conditions, the application of stream simulation to altered stream streams is fully consistent with the Water Crossing Design Guidelines (2013) as well as the Design of Road Culverts for Fish Passage (2003). Rationale for applying stream simulation culvert designs in altered stream systems • Culverts that might otherwise be wider than the artificially constrained channel do not provide additional fish benefits. • In an altered setting, the stream channel can reach equilibrium just as in an unaltered setting. For the purpose of crossing designs this situation may be considered natural channel even though it may have artificial constraints. • Those fish that are present in the channel are not expected to be challenged by the stream simulation culvert which looks and performs similarly to the stream they were just swimming through. • Within limits, these processes and functions can, and are expected to, be unconstrained by a properly designed stream simulation culvert in altered riverscapes: o Flood flow conveyance o Transport of wood o Sediment...