Chinese scientists have unearthed a primitive sarcopterygium that lived 400 million years ago, which is believed to have striking similarities to the common ancestor of the tetrapod and lungfish.Fossil records indicat...Chinese scientists have unearthed a primitive sarcopterygium that lived 400 million years ago, which is believed to have striking similarities to the common ancestor of the tetrapod and lungfish.Fossil records indicate that terrestrial vertebrates (tetrapods), including展开更多
Fish passage is important to the overall health of an ecosystem. Therefore, it is important to be able to accurately predict flow conditions within a stream crossing for high and low flow periods. This paper evaluates...Fish passage is important to the overall health of an ecosystem. Therefore, it is important to be able to accurately predict flow conditions within a stream crossing for high and low flow periods. This paper evaluates the effect of relative water depth on the hydraulic roughness of culverts at low discharge. A 21 m long, 0.8 m diameter corrugated steel pipe with 0.068 × 0.013 m annular corrugations was used. For relative depths below 0.5, Manning’s n was found to increase with decreasing relative depth. An equation was developed to predict relative depths below 0.5 within a corrugated steel pipe based on the corrugation height, slope and culvert diameter. While Manning’s equation does perform reasonably well, the percent difference from the measured to predicted water levels warrants the use of an additional prediction method at low flows.展开更多
文摘Chinese scientists have unearthed a primitive sarcopterygium that lived 400 million years ago, which is believed to have striking similarities to the common ancestor of the tetrapod and lungfish.Fossil records indicate that terrestrial vertebrates (tetrapods), including
文摘Fish passage is important to the overall health of an ecosystem. Therefore, it is important to be able to accurately predict flow conditions within a stream crossing for high and low flow periods. This paper evaluates the effect of relative water depth on the hydraulic roughness of culverts at low discharge. A 21 m long, 0.8 m diameter corrugated steel pipe with 0.068 × 0.013 m annular corrugations was used. For relative depths below 0.5, Manning’s n was found to increase with decreasing relative depth. An equation was developed to predict relative depths below 0.5 within a corrugated steel pipe based on the corrugation height, slope and culvert diameter. While Manning’s equation does perform reasonably well, the percent difference from the measured to predicted water levels warrants the use of an additional prediction method at low flows.
