Heavy encroachment, temporary obstruction in water bodies or natural breaching of lakes led to huge loss of property during Uttarakhand floods, an empowered central committee has said while recommending restrictions on commercial activities in such areas.
The seven-member panel, set up by the Water Resources Ministry, has also suggested creation of an appropriate mechanism on the lines of Coastal Regulation Zone (CZR) to prevent disasters of similar magnitude in the future.
Besides, it has asked Uttarakhand government to ensure implementation of the model Flood Plain Zoning Bill.
The report of the committee said buildings situated less than 50m from river banks were largely washed away during the unprecedented calamity that hit the hill state last year, killing 580 people and leaving over 5,400 people untraceable.
Pointing out that there could have been "possible water hold-up" in the area due to temporary obstruction in natural lake and its subsequent breaching, the committee, however, said that that needs to be established through further study.
The other major reasons identified for high discharges in the snow-fed rivers are melting rate of glacier and unprecedented heavy to very heavy rainfall in the catchment.
At some locations, the report said, debris deposited by the river in its main course during earlier floods obstructed the flow in the central portion, leading to severe erosion of banks and causing the river to shift its course.
Inadequate drainage along the roadside, required to drain rainwater, had also created conducive condition leading to landslides in the region, it added.
The members of the committee had visited various affected sites in Uttarakhand to assess the reasons for the widespread destruction and loss of life and property in the floods of June 16 and 17, 2013.
