SOME HYDROTECHNICAL FEATURES OF PADMA RIVER, BANGLADESH

摘要

The 100-km long Padma River in central Bangladesh carries the combined flows of the Brahmaputra that enters Bangladesh from the north and the Ganges that enters from the west. With a mean flow of around 30,000 m~3/s, a bankfull flow of about 75,000 m~3/s and a 100-year flood flow of around 130,000 m~3/s, in terms of flow it is one of the largest rivers in the world. The boundary materials are mainly fine sand and silt with occasional clay mostly in the upper banks, and the planform and cross-sections are highly unstable over much of the length. Cross-sections are highly irregular in shape, often showing multiple sub-channels, and the gradient is only about 5 cm per km. The overall roughness coefficient (n) declines from around 0.04 at low stage to 0.015 or less at bankfull stage, associated with flattening and wash-out of dunes to an essentially plane-bed condition at high stages. A final note mentions representation of the river bed behaviour in a physical model study designed to investigate bridge pier scour.