https://civilsocietyonline.com/environment/from-avalanche-to-disaster-in-chamoli/
Two separate events occurred on February 7. The first was an avalanche ...This was a natural event..
The second event was the disaster. When such a colossal flood meets a barrier, it smashes the obstruction and moves further downstream with greater energy. In the process it picks up more sediments — rocks and boulders lying on the river bed — and more energy, until the riverbed slope decreases.
The first barrier, a bridge across the Rishiganga, was easily destroyed. The second was the small 13.2 MW Rishiganga hydroelectric project. That was removed.
Then the flood entered the valley of the larger Dhauliganga (West) river. The first barrier on this river was the barrage of the large 520 MW Tapovan-Vishnugad dam. That was swept aside and here the water also entered the intake tunnel. The mouth of the tunnel was blocked by the boulders and other flood-borne sediments. This trapped the labourers working inside the tunnel.
The flood then continued downstream, destroying a suspension bridge near Joshimath and petered out a little later.
Putting obstructions in the path of the flood was the cause of the disaster and this was manmade. Had there been no barrier in the path of the flood, it would have entered the larger Alaknanda Valley and gradually petered out as the bed slope decreased. The damage would have been minimal.
The Bhagirathi Eco-Sensitive Zone (BESZ) from Uttarkashi to Gaumukh, was amended in April 2018 under great pressure from the Uttarakhand government to relax the regulations.
The Ministry of Road Transport & Highways (MoRTH) is lobbying very hard to relax the BESZ regulations in order to widen the highway under the Char Dham Pariyojana.
I am strongly opposed to any relaxation in the original regulations, except the minimum required for defence purposes and transport safety.