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June IAD2016 - Flooding Defense, Design and Innovation

As summer eventually arrives in the North Eastern corner of the Loch Lomond Trossachs National Park, we look back at what was a long and challenging winter with substantial rainfall and flooding reminding us of the power and unpredictability of Scottish Weather.

Year of Innovation, Architecture and Design 2016 logo

The communities of Lochearnhead, Balquhidder, and Strathyre were all affected by flooding as they sustained prolonged periods of heavy rain backed by driving winds, which caused a number of landslips. These were particularly bad around the village of Strathyre, as blocked drainage ditches along the forest tracks, forced water to overspill, carving substantial ditches of up to 2 metres deep on forest tracks, which sent a massive volume of water and grit cascading to an already flooded village. The forestry commission field and more importantly the Broch Café were flooded. Upstream, evacuations were required at Balvaig Cabins with several properties receiving considerable flood damage – some with almost 3 feet of water ingress.

Fast flows in the river Balvaig, with the added debris carried down as a consequence of the blocked ditches caused a high degree of erosion on the river banks. The river Balvaig has a deliberate meandering route towards Loch Lubnaig but with the power of the flow and eroding debris, the river now has lowered banks and bends are straightening, which is not a good situation from a natural flood defence perspective.

With a high focus on the year of Innovation, Art and Design, some thoughts drifted in on innovative measures to address the significant problem of flooding from the river Balvaig. After some study of the river over 3 years by LETi (Loch Earn Tourism Information) group member Kenny Higgins, formerly head of Business Development at Hydro-Logic, based at Stirling University and supported by budding junior Hydrologist, Ceana Heron, some simple measures have been recommended to restore the river Balvaig’s meandering route. As the overspill from Balquhidder known as “Loch Occasional” drains away, the meandering helps slow down the river as it approaches Strathyre and this helps reduce flood risk and erosion impact.

Included in the design of a solution is the need to attempt to restore eroded banks to their former levels. In partnership with River Forth Fisheries Trust and Stirling Council, there is also the plan to plant some willow and other native trees suited to shoring up the existing river banks to help reduce the impact of flooding in future years. An added benefit of the plan is a gradual improvement in the aquaculture of the river and its importance in sustaining a health route for Northbound Salmon to spawning grounds upstream, as well as an improved habitat for Lamprey, Brown Trout and other native species.

It is of course impossible to completely eradicate flooding risk in an area with high rainfall and steep valleys, so we can only do what is possible to slow the fast flow of the river reaching Loch Lubnaig and onwards to River Lenny. This all impacts on the town of Callander and its well-known flooding issues.

During his time in the world of flooding, Kenny designed a Flood monitoring and early warning system, which is now adopted by many Councils throughout the UK and Ireland. It is hoped that Stirling Council may assist the Community of Strathyre with one of Kenny’s designs placed in the river Balvaig so advanced warning may be offered to the residents with property at risk. The design of the system includes Text Alerting and Web based graphs to warn of rising levels, especially useful if such situations are likely to arise during the night. Such systems are already deployed in Callander, Aberfoyle, Killin, Dunblane, Bridge of Allan and several in Stirling.

The plan is a work in progress and budget permitting, we may see some improvements starting to be put in place during 2016.

Broch Door

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Lochearnhead