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A Year of Rain – Review of MulkearLIFE’s Instream Works in 2012

Over the next week, up until the 21st December 2012, MulkearLIFE will be posting articles reviewing the achievements of the project in 2012. These review articles will highlight the very significant achievements of MulkearLIFE’s partners on the ground, namely Limerick County Council and the Office of Public Works and the role of Inland Fisheries Ireland as coordinating partner. The articles will review individual project actions (or sets of actions) according to various key focus areas.

Today, the 12 of the 12, 2012, we start with a review of MulkearLIFE’s instream works. Many people ask, ‘What are Instream Works’ and ‘What are they for?’. In a nutshell, instream works are any form of work, usually involving plant and machinery, which alter the river flow, gradient, bed, channel or banks. The work can be carried out from the river or from the river bank, with a long-reach excavator for example, but only during prescribed time. In an Irish context, this prescribed timeframe, or operational window, is from 1st July to 30th September – a very short window when the weather is not obliging. In the case of MulkearLIFE, all instream work carried out (paired deflectors, rubble mats, strategic placement of random boulders, etc) is done as part of a holistic instream restoration plan, to improve habitats and enhance instream complexity of the river environment for Atlantic salmon and other species. For almost 140 years, much of the Mulkear catchment has been subjected to extensive drainage works. While this has thankfully resulted in the easement of flooding, the drainage works have led to a degradation of habitat and a consequential decline in the salmon population.


Instream Works – All About Increasing Salmon Numbers (Image: Eamonn Pearce)

MulkearLIFE’s instream enhancement measures are designed to mimic natural conditions and have been proven to increase salmon numbers with wider biodiversity benefits. The works do not impact negatively or restrict the flow of water or create a risk of flooding. Rather they greatly enhance the complexity of rivers and riparian biodiversity.


Flood conditions on the Mulkear River, August 2012 (Image: Ruairí Ó Conchúir)

Despite one of the worst summers in 20 years, with high levels of rainfall, resulting in extremely elevated water levels in local rivers throughout the Mulkear Catchment, MulkearLIFE and its project partners (the Office of Public Works and Limerick County Council) were able to implement significant elements of the work plans for 2012.


OPW conducting river enhancement work (Image: Glen Wightman)

Instream Works carried out by the Office of Public Works (OPW) in 2012
The Office of Public Works (OPW), under the direction of MulkearLIFE, completed 3.2kms of river enhancement work on the Newport River. Approximately 675 tons of rock was used to strategically place 100′s of boulders (referred to as random boulders) in the river. Large boulders are a natural physical feature of salmonid rivers and the concept behind the river enhancement work was that the ‘strategic’ placement of such random boulders would mimic those naturally occurring in the river. The boulders provide instream cover which is important from an ecological prospective. They provide protection for a wide range of species and help to create habitat complexity, thus promoting higher level of instream and riparian biodiversity.


One of over 240 random boulders strategically placed (Image: Glen Wightman)

In addition to the enhancement work, the OPW was forced to carry out bank protection work to their flood defences. Flood waters had compromised several sections of Newport river putting homes and farmland at risk. The expert team from the OPW addressed these risks despite the very poor ground conditions.


OPW bank protection work – July 2012 (Image: Ruairí Ó Conchúir)

Instream Works carried out by Limerick County Council in 2012
Limerick County Council, with the support and guidance of MulkearLIFE was scheduled to complete the remaining portion of the Mulkear River Restoration Plan however the summer floods caused the banks of Dead, Reask and Bilboa Rivers to burst flooding hundreds of acres of farmland which led to serious erosion problems.


Limerick Co Co’s work on the Dead River, Sept 2012 (Image: Ruairí Ó Conchúir)

Limerick County Council thus spent the entire summer completing significant bank repair and bank protection work to fix the breaches. This work alleviated erosion which can negatively impact biodiversity. Excess sediment can profoundly affect the productivity of a stream, in a healthy stream young salmonids hide in the interstitial spaces between cobbles and boulders to avoid predation. Clean gravel is also extremely important for aquatic invertebrates, which supply most of the food for young salmonids.


Limerick Co Co’s work on the Dead River, Sept 2012 (Image: Ruairí Ó Conchúir)

If fine sediment is clogging interstitial spaces between streambed gravel salmonids lose their source of spawning gravel, cover and food. The loss of these fish can reduce biodiversity as other wildlife such as grey herons, dippers, kingfishers and otters rely on them as a food source.


Dipper collecting nest material (Image: Ruairí Ó Conchúir)

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Mulkear LIFE, Inland Fisheries Ireland, Ashbourne Business Park, Dock Road, Limerick, Ireland
Phone: +353 (0)61 300 238   Email: limerick@fisheriesireland.ie