Members of the Anti Netravati River Diversion Action Committee, other like-minded outfits and environmental activists took part in the road block agitation at Uppinangady junction.
The blockade and the 'jail bharo' agitation continued till afternoon, before the agitators were arrested and removed by the police.
Committee Convenor Niranjan Rai said the project was being opposed as it was "harmful" to environment and ecology of the region.