The €12 million Lower Morell Flood Management Scheme is not now expected to be completed until 2024 - two years behind schedule.
The project was developed following significant flooding affecting areas including Straffan, Sallins, Naas, in 2009.
The Department of Public Expenditure and Reform notes that the project was "Delayed by approx. 2 years due to Judicial Review".
The scheme has cost €600,000 so far, and the final tally of €12 million includes "ongoing maintenance".