Case Study:

Beach Coastal Protection Works

Background

Garrettstown beach is a 2km stretch of sandy beach located approximately 9km south of Kinsale, County Cork. The beach has sea walls, gabion baskets, rock armour and embankments, all performing as coastal protection measures. During the storms of 2014 in Ireland the gabion baskets suffered severe damage, demanding the consideration of implementing alternative coastal protection measures.

Any method considered needed to allow for the protections of the adjacent regional road R604 from overtopping. Overtopping resulted in sand and other beach debris being strewn across the road, thereby limiting traffic movements in the area. During winter months this was a common occurrence and the road was
cleared repeatedly by Cork County Council at considerable expense.

Solution

In June 2017, an erosion control armour block protection system was installed by Cork County Council to address the issues with coastal erosion and flooding at this location (Figure 1).

The erosion control armour block is an interlocking concrete armour system, which is manufactured from a blend of ordinary Portland cement and ground granulated blast furnace slag. It is considered an innovative, sustainable and cost-effective solution to coastal erosion.

The system allows the concrete to achieve a lighter colour finish and is a more environmentally friendly, stronger, and more durable solution to managing flood risks.

Benefits of solution

Environmental
These units have two direct environmental benefits:
- They are lighter in colour to match the local sands and the voids allow indigenous vegetation such as marram grass to grow between the blocks to enhance their aesthetic and biodiversity appeal; and,
-They allow for the effective protection of the adjacent R604 road from overtopping in storm events.

Economic
The Erosion Control Armour Block system has multiple economic benefits that provide pay-off in both the immediate and long term. They are regular in shape, and are therefore easy to manufacture, transport and place on site. From transport through installation, the sturdiness of the units ensured that they have a high structural strength and can withstand a range of loading types. In addition, the interlocking system exhibits
good hydraulic stability.

As a result of its implementation, the erosion control armour block is expected to reduce Cork County Council’s clean-up costs associated with previous wave overtopping on the nearby regional road.

Figure 1: Erosion control armour block – Garrettstown Beach, Co. Cork.

Project Details:

Timeframe/timescale
On-site construction was programmed to coincide with low tides
and was finalised on site within a four-week period. The works were
completed in June 2017.

Local authority project contact
Kevin Costelloe
Senior Engineer
Coastal & Flooding Section
Water Services
Cork County Council