In 1803 a parliamentary commission drew up plans to build or improve many hundreds of miles of roads throughout the
Highlands. These plans included a number of bridges such as those at Bonar and
Helmsdale. They also included plans for a crossing of Loch Fleet.
As with the other two bridges, the design of the crossing was entrusted to the celebrated engineer Thomas Telford.
He designed a huge earth causeway almost 1000 yards long. At the northern end of this causeway where the River Fleet
flows into the loch he built a stone bridge. Construction work on this huge project began in 1814 and was
completed by June of 1816.
This bridge originally had four arches, although this was later increased to six. Each arch contains a sluice gate
which prevents sea water travelling any further up stream when the tide comes in but allows the river water out as
the tide falls. These gates are self-regulating, but to cope with times when the river is in spate there is also a
mechanism consisting of winches and pulleys to allow the gates to be lifted manually. This was installed, again
under the direction of Thomas Telford, in 1833. Winch houses were built at either end of the bridge and a cottage
for the gate keeper was built at the northern end of the crossing. The winches were recently replaced but one of
the originals can be seen at the museum in Dornoch.
The causeway and sluice gates stop the sea over a mile short of its natural high tide mark. This had a dramatic
effect on the environment upstream of the Mound. The build up of silt in the shallow fresh water created the ideal
conditions for alder and willow trees. The Mound Alderwoods is now one of the largest of its type in Britain and
is a designated nature reserve. The other effect of the building of The Mound was to make the ancient ferry
crossing at Littleferry on the mouth of the loch obsolete.
As well as the main road north, the causeway also used to carry the Dornoch Light Railway from its station in
Dornoch to its junction with the main line at the northern end of The Mound. However this branch line has long since
closed and almost no trace of it remains. Today the main road still crosses the causeway, although it now passes
over a modern bridge, opened in the mid-1980s. Vistors can stop in the car park at the old bridge to admire the
scenery and perhaps watch the salmon making their way back from the sea to spawn in the River Fleet. The returning
salmon arrive with the incoming tide, but as this closes the sluice gates they have to wait in the pool below the
bridge for the tide to fall and the gates to open before they can continue their journey upstream.