Impacts of channelization of River Bala, eastern Himalayan foothills, India

Abstract

Hard river engineering or channelization alters channel bathymetry and river morphology and invites multiple fluvio-hydrological hazards. The linear (72 m), concrete, low height (1.6 m), multipillars (20 pillars) bridge with concrete embankments and revetments has been constructed across and along the river Bala within the Himalayan foothill zone in the year 2017. As a result, the rate of siltation has been tremendously increased at the vicinity of the pillars of the bridge. The principal objectives are (i) to establish wrongly designed hard river engineering techniques and (ii) to find out the adverse effect of Bala bridge. Results showed that the highest rate of siltation was 0.55 m at the end of the monsoon in 2017 whereas the average of rate of siltation was 0.37 m between 2010 and 2017. If the rate of siltation is greater in a particular year, there is a high probability to divert the channel course. The thalweg line has tremendously shifted towards the right bank side. If the same condition persists for a long time, in near future (during monsoon) the river will avulse nearly 200 m right side on low lying topographic depression within the rich Buxa Tiger Reserve.

Keywords

• Siltation
• channel avulsion
• embankment
• revetment