Abstract:
The surface water levels of a river, especially at its river mouth are required for planning and
managing flood alleviation schemes and river engineering works. In lower reaches of a river
flood plain inundation may occur from a high tide in combination with a high flood. Such
studies will help understand the interaction between river flows from upstream and tidal
forcing through river mouth. The results from the study are useful for various govt.
departments that associate in hydrologic design of flood banks and tidal banks; planning
flood plain zoning and disaster preparedness and flood, storm surge vulnerability mapping.
In this study, river flow is simulated using SWMM for the network of nodes that correspond
to locations where cross-section data exists and links that identify stream portion between
two nodes to represent the Gauthami River upto its mouth from just downstream of
Dowlaiswaram. Two scenarios, the first one to simulate for the condition of original flood
banks that existed and second one for scenario where flood embankment are raised to pass
the peak flood studied. The impact of resistance to river flow due to tidal effect and rise in
river level at upstream nodes is large and is about 1.5 m above flood water level in the river
initially and gradually subsides with time as the tidal effect reduces. The head and depth at
two last nodes located representing two outfalls is evaluated. It is observed that the head at
Outfall-1 of the northern branch is well connected to the main river network compared to the
Outfall-2, as the discharge of the river is peaking up and flows during ebb tide to sea. The
complete output of simulation will help draw detailed information on the river flow and river
levels.
