Formerly known as QR National, rail operator Aurizon Holdings Ltd. on Wednesday slashed its full year guidance for coal haulage volumes as it expects the January 2013 floods that affected Queensland would greatly impact operations and earnings.

This as it reported on the same day that first half profits dropped by 10.3 per cent.

It said it expects a more than $40 million dip in its full year earnings, triggered by the floods that unleashed out over Queensland brought by ex-tropical cyclone Oswald. The company likewise blamed a train derailment as another factor to the earnings dip forecast.

Aurizon said that in the six months to Dec. 31, its net profit fell to AU$175.7 million compared to AU$196 million a year ago.

Net profit for the period in review was likewise dragged down by $88 million in redundancy payments, the company said.

Shares in Aurizon fell as a consequence in trading this afternoon, by more than 6 per cent, or 26 cents, to $3.95.

"We see . . . roughly a four million tonne impact as a result of the floods and thus the revision in the way that we describe our guidance for the full year," Lance Hockridge, chief executive, told the AAP.

The company will pay an interim dividend of 4.1 cents a share, up from 3.7 cents previously, on March 27.