(Adds share move in paragraph 3, further details on costs in paragraphs 5-7, adds details on FFI in paragraphs 8 & 9)

Aug 28 (Reuters) - Australian miner Fortescue on Monday reported its worst annual profit in three years, hurt by a one-time cost associated with its Iron Bridge operations amid a surprise senior-management overhaul, sending its shares 5% lower.

The world's fourth-largest iron ore miner, which has been beset by senior management turnover over the past two years, earlier in the day announced the resignation of its metals division head and co-CEO Fiona Hick.

Fortescue shares, up nearly 2.1% so far this year, fell 5.1% to A$19.9 by 0120 GMT.

The full-year profit dropped 23% on declining prices for iron ore and an impairment charge of $726 million related to its Iron Bridge project, a major plank in the group's growth strategy.

Iron Bridge, which has faced multiple cost blow outs and delays in the past, contributes to a life-of mine C1 cost estimate of about $45 per wet metric ton attributable to Fortescue, indicating higher production costs at the magnetite mine.

Inflationary trends impacting construction costs and supply chain delays further stressed the Iron Bridge cost base, though confidence in the outlook for future product prices is expected to offset expenses, Fortescue added.

The company has raised its operating expenditure kept aside for Iron Bridge by $100 million to $4.0 billion, as pooling capital has become increasingly difficult amid high interest rates.

The underlying net profit after tax for the year ended June 30 was $4.80 billion, down from $6.20 billion reported a year ago, significantly missing a Refinitiv estimate of $5.64 billion.

Separately, the company said it would stop allocating 10% of its net profit to fund its green power arm Fortescue Future Industries (FFI), adding, all projects and investments would be assessed under Fortescue's capital allocation framework.

Fortescue Energy is targeting final investment decisions, including cost estimates for five major green projects as early as this year, the company added.

It declared a final dividend of A$1.00 per share, slightly below last year's A$1.21 per share.

(Reporting by Echha Jain and Roushni Nair in Bengaluru; Editing by Rashmi Aich)