Changes in Flow Hydro-Dynamics during Moderate, Typical and Extreme Historical Discharge Events at the Gautami Godavari River Entrance, India- A Case Study

Sibtey Hasan
Godavari is the second longest river (1465 Km) of India, draining approximately 10 % of India’s total geographical area. Several studies have suggested that Godavari delta is morpho-dynamically highly active resulting in shifting of its entrance into the sea. Notably, construction of dams and reservoirs on the Godavari catchment has had profound impact on its flow conditions. It is an accepted fact that changes in flow conditions affect the morphology of the river as sediment transport and flow conditions have a non-linear relationship. In the present study we have tried to investigate the influence of varying flow conditions during extreme events on the Godavari entrance. A two dimensional modelling was conducted using Delft3D tool to investigate the local flow hydrodynamics during extreme events and its effect at the entrance of the Godavari River delta. Based on historical data the current study determined the influence of moderate (20,000 m3/s), typical (40,000 m3/s), and extreme (60,000 m3/s) upstream historical river discharge events in combination with offshore tidal fluctuations on local hydrodynamics at the entrance of Godavari delta. Mathematical modelling results clearly indicated that extreme flood events had a significant impact at the entrance of the river. During moderate and typical discharge events, strong current magnitudes were observed around 2 to 4 m/s off north of Godavari entrance. Most importantly during extreme flood event, after 12 hours of simulation, water started breaching from the shallower point of the existing sand bar South of Godavari mouth and the current magnitude exceeded 4 m/s. It is highly likely that due to such higher current magnitudes during extreme flood events the sand bar itself could propagate further offshore or another narrow opening might be created to the south of the existing entrance towards the sand bar.
Gautami Godavari River; Hydrodynamics; Discharge; Water Level; Coastal Erosion
Download | Back to Issue| Archive