Hydro-morphology of Cuts in Coastal Rivers debouching Chilika; South Mahanadi Delta, Odisha, India

Bhargovi, the split deltaic branch of southern Mahanadi River, runs parallel to Bay of Bengal for last 48.5km and debouches in the northern swamps of Lagoon Chilika joining branch Daya. Though not wide, the river discharges 1100 to 1450cumec which is 3-4% of floods of river Mahanadi. Proximity to coast, alluvial flat topography, sinuosity and mild gradient posed a constant threat to lives and property. Early release of floods to lessen havoc to Puri district during early 20th century was considered urgent. Three cuts were officially provided in the Bhargovi system at. Mangala cut (1937), Siaro cut (1942) and Gabakund cut (1984-2007). After Gabakund cut in 2007, Chilika received 70% less flow of Bhargovi. Sedimentation and imbalance in the flow exchange downsized lagoon area. Each cut plugged one river and made them geriatric or defunct. The present paper studies the spatial impact of these cuts. Stochastic modeling with regression analysis is done to establish a relation between the stages of Gabakund cut vs. discharges at delta head by considering travel time. Field observations are taken to predict the impact of the submerged weir and pilot channel after renovation of cuts.