Council Carries Out Over £100,000 Improvements To Boggan Burn In Dingwall
The Highland Council has carried out over £100,000 of improvement works to the culvert inlet of Boggan Burn in Dingwall following flooding in the town last October. The containment walls to the large silt trap have been raised, the banks of the burn have been raised and reinforced, a new improved replacement inlet screen has been installed, fencing has been altered and extra gullies have been installed in the street. These have been accompanied by a number of other improvements including the installation of a street light to allow for winter inspections.
The Highland Council’s Project Design Manager with TEC Services, Geoff Potter said: “On the 26th October 2006 the eastern side of the Highlands experienced very severe weather conditions including prolonged rain and high winds. The Scottish Environmental Protection Agency has advised that the flows in many of the rivers were the highest on record. The Boggan Burn, which drains a small hillside catchment above Dingwall, was subject to a flash flood which brought down a large volume of debris, silt and gravel. This debris quickly blocked the trash screen inlet to the culverted section of the burn, the burn burst its bank and water flooded into the streets. Drains in the street were unable to cope with the volume of water.
“Now the walls of the inlet structure have been raised to contain rising flood water levels. These raised walls will force water onto the large open grid which covers the silt trap, allowing water to drop into the culvert system as intended. The banks of the watercourse have been raised and reinforced and a new improved larger inlet trash screen has been installed. We have also created more gullies in Burn Place, especially at the low point.”
The culvert had previously given 30 years of trouble free operation and the Council expects the recent improvement works to reduce the risks of any flooding recurrence.
A summary report produced by the Council found that the failure of Boggan Burn drainage was due to the sudden clogging of the inlet, associated with low banks and fencing. During the flood the silt trap and culvert system coped with the flows. However, a full analysis of the flooding at Boggan Burn is still in progress. The Council have employed specialist advisors Dr John Riddell and Mouchel Parkman to give advice on the causes and prevention measures for the flooding. They have also have taken records and have had great assistance from the public, including photos and knowledge gathered from witnesses.
All the culvert systems in the town have now been inspected by the Council. The Gladstone Avenue culvert has been found to be clean and in good condition. However the old culvert in Burn place which is now mainly disused is in poor condition so some improvement works are being carried out on it
Other areas of Dingwall were affected by the flood so the Council has carried out £25,000 of improvements to Ross Wynd and has spent £250,000 repairing damaged on Mitchell Hill.
The last flood study in Dingwall was in 1983, this report does not mention any of the areas where there were recent problems.
Spending in the Highland area following the flood is anticipated to be £6.31 million. Last week the Council received conformation from The Scottish Executive that they would receive a grant of £4 million towards the cost of repairs caused by the storms. The Executive has also said it will further consider what funding might be available in the current financial year for the balance of the damage costs.
Background:
FLOODING
Flooding occurred in October 2006 in Easter Ross, Wester Ross, Sutherland, Caithness. SEPA’s river flow gauges recorded the highest ever flows for many of these rivers.
There were many occurrences of urban flooding. Notably these were in Evanton, Alness, Dingwall and many other locations throughout the area.
OUTFALL AT THE PEFFERY DURING THE FLOOD BOGGAN BURN INLET BLOCKAGE
At the onset of the flood the culvert inlet trash screen became suddenly blocked. This blockage was caused by an accumulation of plastic bags, twigs and grass along with debris, mud and silt.
Once the inlet blocked, the burn burst its bank and escaped into the street causing the flood.
The large silt trap continued to operate satisfactorily but water was prevented from entering by the blocked inlet screen as quick as it arrived.
During the peak of the flood there was a total of 5000 cubic metres (5000 tonnes) of water in Burn Place and Gladstone Avenue. This water accumulated over a period of just 2 hours.