Flood Relief Scheme Arklow Flood Relief

Arklow Flood Relief Scheme Emerging Preferred Option - Public Consultation

Introduction

The Ofﬁce of Public Works (OPW) and Wicklow County Council have commissioned Byrne Looby PH McCarthy (BLP) and Arup to undertake engineering and environmental studies respectively to assess and develop a viable, cost effective and sustainable Flood Relief Scheme for the Avoca River, Arklow.

The process of identifying a preferred scheme to address fluvial and coastal flooding in Arklow includes a detailed assessment of a range of flood risk management measures to determine their technical, economic, social and environmental viability.

Following a detailed scheme options assessment process, the series of measures that will make up the emerging preferred flood relief scheme for the Avoca River, Arklow have now been identified. Following the confirmation of the preferred flood relief scheme an Environmental Impact Statement will be prepared. Why is a Flood Relief Scheme needed in Arklow?

Arklow has suffered from significant flood events in 1986, 1989, 2000, 2002, 2004, 2005 and 2010, resulting in widespread damage to public and private property, primarily in Lower Main Street, South Quay and Ferrybank. The objective of the proposed flood relief scheme at Arklow will be to protect the low lying areas of the town that are impacted during flood events from the Avoca River and the sea.

The flood scheme will be designed to withstand a 1 in 100 year flood event from the Avoca River as well as 1 in 200 year tidal flooding. The flood defences will also be designed to withstand severe tidal events induced by severe weather conditions. Arklow Flood Relief Scheme Emerging Preferred Option - Public Consultation

Work to Date - Environmental Constraints Study and Detailed Options Assessment

Development of the flood relief Following the environmental constraints Some of these measures were Finally, following a detailed, multi- scheme for Arklow has being study, an options assessment process discounted following consideration, criteria analysis of the four options ongoing for some time. To date an was carried out. This process involved and the remaining measures were (each made up of a number of Environmental Constraints Study has the consideration of a number combined into four potential flood measures), one preferred option has been undertaken which identified of potentially suitable flood relief relief options. been put forward by the design team existing features within the study area, measures/combination of measures for detailed environmental assessment which are likely to affect the design for the proposed Arklow Flood Relief - Option 4 and location of the proposed scheme. Scheme.

Some of these measures were Consideration of a number of potentially suitable flood These were then combined to form 4 discounted following consideration, Emerging Preferred Scheme relief measures/combination of measures and the flood relief measures listed potential flood relief options below were brought forward for further consideration

Flood Relief Measures Considered Flood Relief Measures Further Considered Option 1 Option 4

Catchment Management Catchment Management Catchment Management Catchment management Upstream Storage-Single Location Channel and bank maintenance Channel and bank maintenance Channel and bank maintenance Upstream Storage- Multiple Locations Minor modifiations to Arklow bridge Minor modifications to Arklow bridge Debris trap Sluice valves, non-return valves and pumping Flood Storage at Arklow Marsh Sluice valves, non-return valves and pumping Flood defence walls and embankments Flood Relief channel/bypass channel through Arklow Town- Option a Minor improvements to Arklow Bridge Flood defence walls and embankments Flood Relief channel/bypass channel through Arklow Town- Option b Option 2 Lowering of floor of Arklow Bridge by 1m, Flood containment with flood defence walls and Downstream widening on South Quay Flood Relief channel/bypass channel upstream of Arklow Town-Option a embankments Catchment management Upstream and downstream extensive dredging Flood Relief channel/bypass channel upstream of Arklow Town-Option b Sluice valves, non-return valves and pumping Channel and bank maintenance Channel and bank maintenance Minor modifications to Arklow bridge Debris trap Lowering floor of Arklow Bridge by 1.0m Sluice valves, non-return valves and pumping Channel deepening through Arklow (dredging) Flood defence walls and embankments Downstream widening on South Quay Extensive upstream and downstream dredging Debris trap Debris trap Downstream widening on South Quay Removal and replacement of Arklow Bridge Option 3 Minor improvements to Arklow Bridge Catchment management

Flood containment with flood defence walls and embankments Channel and bank maintenance Minor modifications to Arklow bridge Tidal barrage- Option a Sluice valves, non-return valves and pumping Tidal barrage- Option b Flood defence walls and embankments River barrage Lowering of floor of Arklow Bridge by 1m, Sluice valves, non-return valves and pumping Downstream widening on South Quay Lowering floor of Arklow Bridge by 0.6m Upstream and downstream extensive dredging

Lowering floor of Arklow Bridge by 1.0m Option 4 Lowering floor of Arklow Bridge by 1.5m Catchment management Lowering floor of Arklow Bridge by 1m and local upstream dredging Channel and bank maintenance Lowering floor by 1m, and downstream widening at contraction location Minor modifications to Arklow bridge

Lowering ﬂoor of Arklow Bridge by 1m, downstream widening and upstream and downstream extensive dredging Sluice valves, non-return valves and pumping

Lowering ﬂoor of Arklow Bridge by 1.5m, downstream widening and upstream and downstream extensive dredging Flood defence walls and embankments Lowering of ﬂoor of Arklow Bridge by 1m, Downstream widening on South Quay Upstream and downstream extensive dredging Debris trap Arklow Flood Relief Scheme Emerging Preferred Option - Public Consultation

Emerging Preferred Scheme - Overview

1 Flood defence walls

2 Flood defence embankments

3 Lowering of ﬂoor of Arklow Bridge by 1m

4 Downstream widening on South Quay

5 Upstream and downstream extensive dredging

6 Debris trap (indicative location)

Emerging Preferred Scheme

The emerging preferred Arklow Flood Relief Scheme is made up of a combination of ﬂood relief measures consisting of:

• Catchment management • Sluice valves, non-return valves and pumping • Downstream widening on South Quay • Channel and bank maintenance • Flood defence walls and embankments • Upstream and downstream extensive dredging • Minor modiﬁcations to Arklow bridge • Lowering of ﬂoor of Arklow Bridge by 1m, • Debris trap

1 Flood defence 2 Flood defence 3 Lowering of ﬂoor of 4 Downstream 5 Upstream and 6 Debris trap walls embankments Arklow Bridge by 1m widening on downstream South Quay extensive dredging

Tidal and Fluvial flood defence Flooding events have affected Lowering the floor of Arklow It is proposed to remove a local It is proposed to dredge the bed A debris trap is proposed to walls are required upstream and properties in Ferrybank when Bridge will require the all of the narrowing of the channel on the of the river by approximately 300m collect large items of debris downstream of the Arklow bridge flows were conveyed through piers of the bridge to be extended south bank. This will involve upstream of Arklow Bridge and such as tree branches etc. and in the locations indicated on the marsh. To prevent this from downwards by approximately removing a tapering section 500m downstream. The depth of prevent them from blocking the the scheme drawing. The flood occurring, earth embankments 2m. The existing river bed will of bank of up to 10m, over a dredging will be up to 1m. This arches of Arklow Bridge. It will be defence walls will extend along the will be constructed to ensure that then be lowered by 1.5m. A new length of 160m. This will result will increase the capacity of the constructed from vertical pillars. right (south) bank of the river from all properties below the predicted 250mm thick concrete slab will in less sedimentation and thus channel to cater for river floods The location of the debris trap the existing slipway by the carpark design flood levels are protected. be placed on the new river bed a lower maintenance dredging and together with the lowering of shown on the adjacent plan is upstream of Arklow Bridge, to the of the river, extending upstream requirement. the floor of the bridge will reduce indicative. This will allow floods Dock downstream of the bridge. and downstream of the bridge flood levels by up to 540mm for to flow through the marsh in in order to prevent scour of the the 1 in 100 year flood event. the event that the debris trap These walls will defend the low new bed and the piers. 250mm becomes partially blocked. lying areas along the south bank of gravel will be placed over the Access to clear the debris trap is of the river from the 1 in 100 concrete to restore the natural envisaged to be from the south year flood event from the river appearance of the river bed. The bank. upstream of Arklow Bridge and the net reduction in the bridge floor 1 in 200 year coastal flood event level will be 1m. At present, Arklow downstream of the bridge. The Bridge is a significant restriction walls will be of reinforced concrete to flood flows. Lowering the floor construction. Stone cladding may of the bridge by 1m, together be used where compatible with with upstream and downstream existing structures. dredging, will reduce flood levels by up to 540mm immediately upstream of the bridge.

General Scheme Measures

Catchment management Channel and bank maintenance Minor modiﬁcations to Arklow bridge Sluice valves, non-return valves and pumping

This includes measures such as surface water retention, This involves the removal of unwanted vegetation and This involves the re-pointing of the bridge pier mortar joints The aim of this measure is to prevent ﬂooding caused by water treatment and rainwater harvesting. These will deposited material from the Avoca River channel and its in order to guard against damage from internal erosion and rising river levels backing up through sewers and drains reduce the impact of surface water run-off from new banks downstream of the M11 Bridge as far as Arklow extending the existing scour apron across the full width of that discharge into the river. developments on the Avoca River, improve the quality of Bridge to maintain the design channel and bank roughness the river upstream of the bridge. the water being discharged to the river and reduce the coefﬁcients. overall potable water demand in the area. Arklow Flood Relief Scheme Emerging Preferred Option - Public Consultation

Your Feedback is Important

The OPW and Wicklow County Council wish to consider all viewpoints relating to the emerging preferred option for the proposed Arklow Flood Relief Scheme.

Please complete the Questionnaire and place it in the box provided. Or, alternatively you can write to:

District Administrator, Arklow Municipal District, Castle Park, Arklow, Co. Wicklow Email address: [email protected]

RelatedThe purpose Ongoing of this Public Project: Information The Day Proposed on the emerging Arklowpreferred Wastewaterﬂood relief scheme Treatment is to: Plant

At present, inform untreatedthe public wastewater and stakeholders from homes of the andprogress businesses made in Arklowsince is the discharged project commenced; into the Avoca River that runs directly through Arklow Town. This practice of discharging untreated describe the scheme options assessment process; wastewater to the river is no longer acceptable and Irish Water provide intends information to ﬁx this problem on the emerging in partnership preferred with schemeWicklow for Countyalleviating Council ﬂoodingby developing Arklow this town; project and which will include:

• A ascertain new Wastewater the opinions Treatment of the Plantpublic (WwTP) on the whichemerging will treatpreferred an estimated scheme 36,000 and gather PE (population useful local equivalent) information that willthat best may meet inform the the current ﬁnal needsscheme of design Arklow, and and associated to allow forenvironmental future expansion assessment. of the town. The preferred site for this plant is the Old Wallboard Factory, North Quay, Ferrybank; • Sewer pipelines to bring untreated wastewater to the WwTP; • A marine outfall pipe to safely discharge the treated wastewater to the Irish Sea. Irish Water, the OPW and Wicklow County Council are working together to minimise any potential environmental impacts and inconvenience to the people of Arklow while delivering these critical infrastructure projects. Environmental Impact Statements (EIS) will be prepared for both projects and each EIS will consider the potential for cumulative impact from the delivery of both projects.

For more information on the wastewater treatment plant project, please visit www.water.ie/arklowtp