Home to 9,000 residents, the picturesque town of Forres, in Moray, Scotland, dates back to Roman times. However, the town was blighted by severe floods in 1997 and 2000 when the Burn of Mosset, which flows through the centre of Forres, inundated homes and businesses and severely affected the local economy.
In 1997, 430 residential and 27 commercial properties were flooded at an estimated cost of £3.7 million. Hundreds of residents had to vacate their homes and move into shortterm accommodation, and the main rail and road transport links to the area were forced to close temporarily.
It was estimated that without intervention flood damage in Forres would exceed £43 million over the next 50 years. Future flooding would not only affect homes, businesses and the economy of the town and surrounding region, but would also put the area’s schools, emergency services and sewage works at risk.
Appointed by The Moray Council in 2000, Royal HaskoningDHV was part of a team whose challenge was to find a costeffective, sustainable solution to alleviate flooding in Forres, as well as nearby Lhanbryde and Elgin. The team combined expertise from Royal HaskoningDHV, The Moray Council, the principal contractor Morrison Construction, and more recently cost consultant EC Harris.
Royal HaskoningDHV has extensive global experience of designing, constructing and managing flood alleviation schemes and was able to use this expertise at all stages of the project. A range of proposals were considered, with Royal HaskoningDHV leading the data collection and option appraisal, advising on the design stages and estimated costs and benefits, then finally supervising construction, which began in November 2007.
Prior to the scheme, the flow capacity of the Burn of Mosset though Forres was insufficient to convey flood flows without inundating properties. It was agreed that the most appropriate solution was to construct a large flood storage reservoir on the Burn of Mosset at Chapelton. The flood storage reservoir is formed by a main dam (Chapelton Dam) across the Burn of Mosset and two smaller dams on the periphery of the reservoir. There are also minor flood defences within Forres itself.
The flood storage reservoir makes use of a large natural basin upstream of Forres that drains through a narrow valley at Chapelton. A cost effective and practical solution, the reservoir has a 3.8 million cubic metre capacity and stores excess water during high-flow events.