Blocked outfall pipes, heavy rainfall and saturated ground were the main causes of flooding at 34 properties in or close to Llansteffan last winter, a report has concluded.

A flood in the picturesque village on December 30 was followed by a more serious one on January 2, coinciding with two named storms and following the wettest autumn in Carmarthenshire for 189 years. Most of the affected homes were on The Green – a low-lying road close to the estuary beach.

Some residents used corrugated sheets to try to divert floodwater over-topping the Nant Jac watercourse, while others filled sandbags. “Several residents noted that they felt helpless in the face of the flooding and did not know the actions they should or could be taking to respond or reduce the impacts,” said the report into the floods commissioned by Carmarthenshire Council.

Referring to the January 2 flood, the report said: “During this event the ground was so saturated that as residents of two properties were attempting to prevent flood water ingress through doors/entrances, that floodwater was seeping up through the internal ground flooring of properties.”

A summary of the key findings said the flooding was “generally the result of increased surface water flows entering various watercourses which could not cope and over-topped”.

It added: “Flooding was worsened by the fact that the key outfall draining the surface and flood water was buried under the beach and floodwater from the first storm wasn’t effectively drained ahead of the second storm.”

Two days after the second flood the council excavated sand blocking a main outfall. This allowed water that was being held back in storage chambers to finally drain out.

The interaction between the storage chambers and outfalls was, said the report, a potential “critical point of failure”. It added that the council was excavating the outfall after high tides as an interim measure pending the identification of a long-term solution.

The report also said that while the principal authorities responded during and after the flooding, co-ordination and communication could have been more effective.

Other issues identified were manhole covers not being watertight, and the possibility that property and highways surface water drains were connected into the public sewer network, adding to the load.

The report also said the area above Llansteffan included a lot of agricultural land and that there were “issues with high levels of sedimentation” in water run-off affecting properties upstream of The Green.

Flooding has happened previously on low-lying parts of Llansteffan, and drainage improvements work was carried out in 2015. The new report has recommended a series of short, medium and long-term actions, including 11 about operation and maintenance.

Liz Dutch, who lives with her husband on The Green, said their property hadn’t flooded since they bought it in 1996 although occasionally water seeped up in the garden.

Mrs Dutch said they were luckier than many other residents as only around three inches of floodwater affected their home last winter. But she said standing water surrounded it on three sides for five or six days. The worst affected room, she said, was the utility room as it has a suspended timber floor.

“We are still living in a total mess,” said Mrs Dutch. “We are about the last people here trying to get ourselves sorted. It has been an absolute nightmare.”

Mrs Dutch said the insurance process has dragged on and on and that eventually she and her husband sought a cash settlement so that they could use local builders rather than ones a long way away that had been appointed by her insurers. She said she and her husband were still awaiting the last of three cash instalments.

Mrs Dutch said she felt nervous now when heavy rainfall was forecast and that the cost of insuring the property more than doubled at renewal, but she added: “As I have said all along, there are many worse things happening in the world today. We are still alive and our house didn’t collapse.”

Cabinet approved the report’s findings at a meeting on December 2.

Cllr Aled Vaughan Owen, cabinet member for climate change, decarbonisation and sustainability, described the 80-page report as a “thorough analysis”.

He said it showed the complex nature of a “significant” flood event influenced by topography, land use, weather conditions, time of year and local infrastructure. He thanked people in Llansteffan and everyone involved in the recovery and investigation work.

Earlier in the meeting cabinet endorsed an updated county-wide flood risk management strategy, which said 12,609 properties were at high, medium or low risk of flooding in Carmarthenshire.

Cllr Vaughan Owen said the two reports demonstrated the “urgent need to tackle the runaway climate breakdown that we are facing” and ensure there was sufficient funding to adapt and improve ageing infrastructure for “an uncertain and unpredictable future”.