In Autumn 2000 The village of Rhydymwyn, in the upper reaches of the Alyn catchment, was severely effected with approximately 68 homes and 8 businesses flooded.
Across North Wales and in particular North East Wales the rainfall event of Autumn 2000 was exceptional in terms of intensity and duration. The event started on 28 October and continued into November culminating on the 6 November. The result was wide spread flooding of property and land. One of the worst effected areas was the River Alyn Catchment.
The village of Rhydymwyn, in the upper reaches of the Alyn catchment, was severely effected with approximately 68 homes and 8 businesses flooded.
At the time of the floods Rhydymwyn did not benefit from either a formal flood warning scheme or formal flood defences.
In the aftermath of the floods the Agency identified a number of both short term and long term actions required to prevent flooding on a similar scale within Rhydymwyn.
The short term actions were implemented immediately. These included constructing a temporary sandbag wall on left bank of the River Alyn and a temporary flood warning scheme.
The long term actions included formalizing the flood warning scheme and constructing a flood alleviation scheme to protect the village.
Having considered in detail a number of options for the proposed flood alleviation scheme a decision was made to undertake the work through the Agency’s revenue budget as a small improvement scheme.
Consequently all Design, Contract Management and Planning Supervision (Under the CDM Regs 1994) was undertaken by Agency staff in the area office at Buckley.
The scheme briefly comprised of: a 66m long concrete Floodwall constructed along the left bank of the River Alyn (upstream of the road bridge), an overflow channel through the field on the right bank of the River Alyn (upstream of Rhydymwyn Road), 5 concrete flood relief culverts under Rhydymwyn Road, a concrete overflow channel through the DEFRA site and alterations to the existing concrete channel, containing the River Alyn, within the DEFRA site.
Construction work was undertaken by the Agency’s ‘In-House’ contractor in two phases. The first phase, construction of the floodwall, was undertaken in early 2002. The second phase of work, the remainder of the scheme, was completed in May 2003. The finished scheme has provided a level of protection in excess of a flood with a 1% chance of occurring in any one year.
Total cost for the scheme was £88, 000.
In addition to the Flood Alleviation Scheme the Flood Warning scheme has been formalized into a full 4 stage scheme and the river level gauging/warning station has been upgraded.