Justification
Flood risk management plan
The West of Wales SMP2 and Western Wales Flood Risk Management Plan have identified that in the Barmouth area “there would be significant increases in flood risk and sea level rise” and recommends that long term planning should look at “realignment and redevelopment… to provide a more secure future for development of this waterfront area”.
The case for change
The area is subject to flooding from two primary sources. Firstly, the runoff from the hillside, Dinas Oleu, located directly behind the town currently overwhelms the highway and combined drainage systems. These drainage systems also become tidally locked. The water ponds at depressions behind the defences, flooding the main road (A496) and several properties in the area.
The second source is coastal flooding. The wave climate at the harbour amplifies waves on the approach at the Gerddi Cae Glas frontage. This results in wave generated overtopping at a rate which overwhelms the existing infrastructure.
The area has suffered a number of flooding events over past and recent years and there are growing fears that intensity and frequency of these events are likely to increase over future years, along with climate change estimations including sea level rise. In combination, the existing sea wall defences suffered a partial collapse in 2020 following storm damage and continue to deteriorate.
The project provides a Standard of Protection (SoP) of 1 to 200 year (+50 years of climate change) to a total of 31 properties (24 residential and 7 commercial + the electricity sub station).
History of flooding:
The southern region of Barmouth has experienced several flood events over past and recent years. Two significant flood events took place in 2014 and 2020.
2014
In January 2014 a series of Atlantic low-pressure systems generated significant storm surges and relatively powerful waves, which in combination with high tides caused considerable disruption along the Welsh coast. Flood and coastal defence structures were damaged and severely tested, and in some locations, defences were breached causing damage to property.
12 properties around the harbour were flooded internally: 6 residential and 6 commercial. The majority of these properties were located on Church Street and were inundated by wave overtopping at Viaduct Gardens. The public conveniences at the harbour were also flooded. The properties flooded at the harbour are within a NRW Flood Warning Area.
2020
Following winter storms in 2020 significant damaged was caused to the existing sea wall at Viaduct Gardens. The current sea wall does not provide an adequate standard of protection to this part of the Town, and with the standard of protection reducing further with the effects of climate change. Meaning that more regular flooding would be experienced in the absence of any further intervention. This partial collapse of the sea wall has been temporarily halted by the inclusion of rock armour in front of the wall and propping of the sea wall stones with sandbags.
Proposed scheme:
The scheme design comprises of:
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Rebuild and raise of the existing sea wall below the Network Rail viaduct,
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Rebuild and raise of the gardens boundary wall (raised with a glass panel top)
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Installation of 4 new flood gates
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New below ground surface water with a below ground pump
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New outfall on the beach
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New rock armour in front of the wall and around the new outfall
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Installation of property level measures along the Quay properties
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Relandscaping of the gardens area
Timescale and Funding:
The construction phase will be funded through the Coastal Risk Management Programme (CRMP).
The current time frame for the project is:
January 2024
Release the works to tender, to appoint a contractor.
Mid-February 2024
Appoint, in principle, a contractor.
Late February 2024
Submit final business case to Welsh Government for approval.
March 2024
Subject to approval, finalise appointing of contractor.
April 2024
Subject to successful contractor’s programme, construction phase will begin.
November 2024
Construction begins
Winter 2026
Completion of construction works
Barmouth – Viaduct Gardens flood prevention scheme
FCRMU@gwynedd.llyw.cymru
YGC | Ymgynghoriaeth Gwynedd Consultancy
Shirehall Street
Caernarfon
Gwynedd
LL55 1SH
(01286) 679426
