Hydraulic characteristics of the Jamuna River gauging section, Bangladesh

The Jamuna is a large braided river in Bangladesh, characterised by high seasonal variability in flow, with a mean discharge of nearly 20 000 m³/s. Hydraulic characteristics of the gauging section have been investigated by analysing the cross-sectional parameters, velocity, discharge and local water surface slope data based on two consecutive years of intensive measurements. The water surface width was more than 8 km during high flood conditions in both years. The gauging section is not stable because of severe erosion and deposition during monsoon. The stage–discharge relationship varies from year to year as well as within the year. The geometric and resistance characteristics during decreasing flow can differ from those during increasing flow. The resistance to flow at flood stage is quite small compared with that at low stage. The stage–discharge curve for a flood wave forms a clockwise loop which is in contrast with the familiar anticlockwise loop. An improved fit of the yearly stage–discharge relationship can be obtained by dividing the annual data set into four subsets to represent different hydraulic conditions.