Aberfoyle is a village on the banks of the river Forth about 20 miles West of Stirling. Aberfoyle is the main settlement of the community of Strathard, which takes in the area west of Aberfoyle up the Duchray Valley and the valley of Lochs Chon and Ard. Strathard is served by just one road, the B829, which is a 20km long cul-de-sac running from Aberfoyle and terminating at Inversnaid on Loch Lomond and Stronachlachar on Loch Katrine. The Forth is a large river basin in Scotland. It flows eastwards, rising on the slopes of Ben Lomond, through Stirling and into the Firth of Forth. Aberfoyle suffers from serious and frequent flooding. Flooding there is considered to be “high likelihood”. Flooding has damaged businesses and domestic housing in and near the village and westwards along Strathard.

Flood risk management is regulated by statute and Scottish Government Guidance. An overarching outcome in the Guidance is to use space available to store water and slow down the progress of floods. Flood risk management is to be assessed on the basis of river catchments not administrative areas. This includes the Duchray catchment which is a main source of the worst peak flood river flows in the Forth. It also includes measuring the effect downstream in Stirling and the Carse of Stirling of upstream structures to store peak flows.

Stirling Council, working with SEPA, produced a flood risk management plan based only on prevention of direct property damage in Aberfoyle. This involved construction of high flood walls and bunds in the village. These would have adversely affected the amenity of the village and were opposed by the local community. The effect of peak flood flows goes far beyond direct property damage in Aberfoyle. There are also indirect and consequential property losses. They affect the local school and cause considerable damage to local businesses and inconvenience to local residents and visitors. Floods prevent access along the road westwards to Strathard affecting existing businesses and future commercial development. Forth peak flooding affects agriculture in the Carse of Stirling, and property in Stirling and Bridge of Allan.

A report made in 2017 by Mouchel, civil engineering consultants, which recommended construction of high flood walls and embankments in the village, also explored 3 sites in the Duchray catchment which were suitable for storage of peak flood flows. The most elevated site would reduce flood flow levels in Aberfoyle but not enough to protect property without further measures. The two other sites considered have the potential to store substantial peak flood flows. They were not considered by Mouchel as potential further measures.

Mouchel also compared the cost of their recommended flood walls and embankments measures with benefits which they assessed. Their assessment of benefit was limited to avoiding direct property damage in Aberfoyle. The cost of their recommended measures as they reported it was £8.5M. As presented for government funding it had increased to £16M. This could not be justified when compared with the assessed benefits.

This report recommends further investigation of all three potential areas for successive storage of peak flood flows in the Duchray catchment. Increasing the capacity of storage in this way has the potential to benefit not only Aberfoyle and Strathard but also agriculture in the Carse of Stirling, Stirling itself and possibly Bridge of Allan. In Aberfoyle we propose also that the level of the B829 West of Bailie Nicol Jarvie be raised.

The cost of these proposals would be entirely different from the cost of the previously recommended measures. As the storage structures would be separate, the works could be divided into phases as funding became available. The benefit of these proposals would take into account damage avoided downstream and in particular in Stirling. Dealing with flooding at source rather than its direct effects would much improve practical and economic outcomes.