Curlver hydraulics with respect to ecological migration

摘要

Nowadays culvert design has to meet several requirements: flood control or flood mitigation and preservation of ecological migration. Since earlier design aimed at passing a design flood without an excessive headwater elevation, today's culvert hydraulics has to prove that a culvert will not become a barrier to normal migration routes of land animals, amphibious and aquatic animals. Hydraulic considerations are focussed on 3 different design flows: Design flood, to control headwater elevation and scour conditions, average flow, to compare flow velocity with top speed of migratory fishes, low flow, to make sure that water depth is never less then 0.2 m. Nonuniform flow through culvert is governed by the Bernoulli-Equation and involves entrance loss,friction loss and outlet loss. One problem facing the designer is to find the location of flow changes from subcritical to supercritical and vice versa. The calculations may be performed by EXCEL or Mathcad.