More than 400 properties were flooded in Wairoa in torrential rain on Tuesday and Wednesday.
Council chairperson Hinewai Ormsby told Nine to Noon decisions about opening the Wairoa bar were made on the best information available at the time.
"The difficulty and the challenge, which has been longstanding, for the management of the Wairoa mouth opening has been the level in which the riverbed is at versus the swell and tide, and the timings and complexities around getting that right for the sake of human safety ... as well as it being successful to actually open it.
"To move one bucket of shingle and have it fill up with two just minutes later will not be a successful opening," she said.
"But acknowledging that we do all agree that had it been opened sooner we wouldn't have seen the devastation that we have in Wairoa."
Ormsby said the council would review its processes to see if the decision should have been made sooner.
"I want to be fully briefed from our operations team on that process, and whether or not it could've been triggered earlier and what we need to improve that.
"I think there is a definite need to re-look at including far more local knowledge ... we need to make sure those improvements of local knowledge have an input into the earlier decision-making."
A review of the region's flood protection was due to be published next month and would include a look at how its 19 rivermouths are managed.
"I will note that we have Nuhaka and Waitahuna open successfully over the weekend and we were able to do that in precaution, but I think we all agree that the Wairoa mouth, its significance, its longstanding problems in engineering it, opening it successfully, has been very difficult and wasn't successful."
A contractor who has worked on the bar for decades says there may have been a risk assessment failure and the decision to do the work came too late.
Hamish Pryde said crews had been put on notice on Friday - "at that point someone had obviously assessed there was a risk". The go-ahead was not given until mid-afternoon on Monday.
"I guess that risk has been sat on until Monday afternoon - it's not really for me to decide whether that was a fair call.
"Without pointing the finger that's clearly, assessments were made and we ended up flooding. So I guess the risk assessment by someone was faulty.
"Realistically the storm was already upon us by the time we got the go-ahead to go and do that so we were always on a losing battle ... but you've got to appreciate we are dealing with mother nature. I think no one really expected to get the level of flooding that we did."
Regardless of the conditions, the company needed a few days' lead time to mobilise and prepare the site, before attempting to open a new river mouth.
Pryde said given that peoples' houses and livelihoods were at risk there should have been a bigger emphasis on the side of caution.
His crew finished work in the dark on Tuesday, the night before the flooding, and left their equipment in the same spot they had parked for 20-30 years - high up and away from the sand bar. However, they were flooded up to the top of their cabs.
He said the lagoon had no natural outlet to the sea, and has essentially been controlled by humans since his father's day, when it was dug out with horses and shovels.
Ocean currents and waves constantly moved the gravel at the bar causing it to prevent the river from draining properly.
Pryde had previously gone ahead and done work without waiting for the council nod - he was labelled a hero for his efforts in 2022.
