Thanks for the nice comments
akroy: There is a left turn just after kanakpura town (approx 500 mts) , this road goes to cauvery sangam (there is a direction board in the corner by karnataka tourism). take this route and keep going straight (approx 35 kms ) , you will see a left turn for chunchi falls. If you keep going staright you will reach sangama. you can park the vehicle in the restaurant at the entrance (nice food btw).
You need to take the bus to reach the ravine (5kms) , it is available across the river. yes we need to cross the stream! (bus ticket 40rs /head to &fro).Hope that helps..