River-tide-storm surge interaction characteristics for the Hooghly estuary, East coast of India

Abstract

ABSTRACT The head Bay of Bengal region that borders the North Indian Ocean is crisscrossed with numerous tidal creeks, riverine systems and channels that play an important role in storm surge studies. In particular, the storm surge resulting from the landfall of tropical cyclone over this region can interact with the river systems and thereby modify the characteristics of storm surge. Several studies were attempted to understand the behaviour of storm surges and associated inundation for the Indian coast; however, the role of hydrologic component in modifying storm surge received less attention. The present study considers a stretch of Hooghly River channel in West Bengal that provides the navigable route to two important national ports, and important in context to socio-economic implications. The state-of-art advanced circulation model (ADCIRC) hydrodynamic model used in this study incorporates the riverine stretch and investigates the effect of river discharge on storm surge propagation along the upstream reaches of the Hooghly River. In addition, the river-tide interaction was studied with differential river discharge volumes of 1000 and 3000 m3 s−1 that corresponds to the respective minimum and maximum discharges. Model simulations well represented the upstream tidal propagation as well the reversal of tidal currents in the river. Also the effect of variable river discharge volumes in modifying the limit of flood flow was clear from simulation. The results signify that limit of flood flow was seen nearly 70 km in the river upstream for discharge volume corresponding to 1000 m3 s−1 and reduced to 62 km on increasing the discharge to 3000 m3 s−1. The effect of wind stress on storm surge penetration into river was also investigated using the hypothetical Aila cyclone wind field. Moreover, the combined effect due to varying river discharge volumes and wind stress on storm surge characteristics was also studied. The study is an effort to understand the role of river-tide-storm surge interaction very useful in a real-time storm surge forecasting system.