Hydraulic conveyance enhancement and flood mitigation in the Bagjola drainage canal: insights from 1D Hydrodynamic modelling and dredging scenarios

This study deals with how dredging influences flood behaviour and water level dynamics in the low-gradient Bagjola Drainage Canal in Kolkata, which is affected by tidal influences from the downstream Bidyadhari River. The evaluation of dredging-affected flood dynamics was carried out using a MIKE+ hydrodynamic modelling approach under actual storm event conditions. To achieve this, two dredging scenarios – partial dredging (Scenario A) and full-extent dredging (Scenario B), were compared against a baseline condition. According to scenario simulations, partial dredging reduced flood levels by 50–60 cm in the upstream locations. On the other hand, full dredging reduced flood levels by 0.9–1.2 m, especially in the middle of the canal sections, with reductions of up to 97% at some locations. Bagjola Canal modelling results indicate how dredging scenarios significantly improved hydraulic efficiency locally, and also offer broadly applicable insights for urban flood management in low-gradient, tidally influenced regions.