Dam emergency leaves California countryside scarred

The devastation caused by frantic measures to shore up the tallest dam in the US has been revealed.

A flyover video taken by California's Department of Water Resources shows the damage wrought on the Oroville Dam spillway and surrounding countryside from last month's emergency caused by a massive deluge across the state.

State government officials were forced to drain Lake Oroville last month and the releases of water had to travel as quickly as possible, reports usatoday.

This involved 2830sqm of water hurtling every second down the damaged concrete spillway.

Dramatic footage showed how it took cement, trees, earth and other debris with it. The force of the water also created a ravine to the south of the spillway.

The huge escape of water has left workers with a massive clean-up task.

The emergency began last month when heavy rainfall prompted concern about the dam's infrastructure and required almost 200,000 people to evacuate their homes.