Article that explains basic geografy of Scotland important to know for visiting fly fisherman.
Jutting out bravely into the eternal swell of the northern Atlantic provides Scotland with several major features which influence her fishing. The types of rock and ages of geological turmoil affect the topography of the land and, consequently, its aquatic environments; but other factors combine to make this region unique. These include the temperate oceanic climate and the persisting effects of the last Ice Age. The geological processes that shaped the landscape are still at work. The ancient rocks are still being ground away by the relentless effects of weather. Nothing stays the same, a fact that is obvious to the river angler who will often see the shape of his river changing as its course is reworked by winter floods.
Scotland has three main geological regions differentiated by their location and form. The first is the great expanse of the northern Highlands, which includes the Hebridean and Northern islands. It is a wild, mountainous area bounded in the south by the Highland Boundary Fault - the joining of two tectonic plates of the Earth's crust. The Highland Boundary Fault is marked along much of its length, by high ground to the north and low ground to the south. Some rivers tumble over the fault line, while others run through the great swathe of the low ground below. The valley of the River North Esk, near Edzell, presents a fine opportunity to stand astride the actual line of the Highland Fault, while the glens of the Rivers Tilt and Garry show where lava forced into the Fault's side cracks, to form igneous dykes over which the rivers tumble and foam.
The second region is the sweep of the Forth/Clyde valley known as the Central Lowlands. Here the rivers are wide and slow running. The River Forth meets the sea close to Scotland's capital city, Edinburgh, and the Clyde does the same near Glasgow. The greatest salmon river, the Tay, also runs through the central Lowland plain before it meets the North Sea. The third main geological region is the hilly Borders region known as the Southern Uplands. Here the rivers run through gentle valleys, many being tributaries of the mighty Tweed.
The rocks of the Highland north are mostly very ancient and metamorphic, with quartzes, gneisses and schists predominating, basalts and other igneous intrusions fill in the spaces. The Central Lowlands is a valley consisting of sandstones and other metamorphic conglomerates of younger age. The Southern Uplands are similar in geology to neighbouring north England, with folded and fractured metamorphic rocks showing the general north-east to south-west fault orientation. There are outcrops of various rocks in most areas, some with significant influence on fishing. A prime example being localised limestone of the far north and west, which brings richness to the aquatic environment.
Countless aeons of battering by oceanic waves and above-average rainfall have worn the west coast into a deeply-etched system of fjordic sea lochs and islands. The west coast valleys carry spate rivers flowing mostly over bare rocks, and freshwater lochs where water is trapped in peaty glacial valleys. The effects of glaciation are visible everywhere. Smooth rocks polished by the ice sheets; deeply-cut glacial valleys show the tremendous sculpting power of the ice; and m many valleys there are raised beaches showing where seas once lapped at heights unimaginable today. In most valleys there are moraines - sediment deposited by glaciers - left behind following the melting of thousands of feet of ice at the end of the last Ice Age.
The east coast of Scotland is quite different from the west. Here the land tends to be much gentler in character with fewer, but longer rivers. Similarly, there are fewer lochs, perhaps due to lighter rainfall. The land slopes from the massif of the central Highland plateau towards the North Sea, and down this incline flow some of the most famous salmon rivers in the world including: the Tay, the Tweed, the Dee and the Spey.
For hundreds of years, major changes to Scotland's original landscape have occurred due to the impact of agriculture and forestry. The forests, which once stood throughout the country, were decimated for fuel or cleared for farming. The great Caledonian pine and oak forests are long gone, although you may still see the remaining vestiges on the island of a remote loch. There you may see red-trunked Scots pines providing a canopy over smaller hazels, birches, willows and alders. Birch forests have taken over where the great pine and oak trees once stood, but the planting of non-native conifers is the feature that most signals man's intervention through forestry. Many glens are flanked by mono-cultures of Sitka spruce and larch, although more-enlightened planting over recent years has seen the return of mixed deciduous trees. Many of our river banks have retained tracts of native species trees and are all the more attractive for this.
Man has also transformed the shape and course of many of the waters of Scotland. This process was at its height during the early part of the Industrial Revolution, where water power was essential for industry. Water, taken from dams, often comes from well below the surface of the impounded loch. The water may be cooler in high summer - an advantage - but may be less well-oxygenated - a temporary disadvantage - as the water should soon be aerated particularly if turbulent. Such water may also show variable chemical composition due to differential absorbance of nutrients at different temperatures and pressures in the dam above. On a practical level for anglers, keep in mind that the sudden onset of generation may create a very rapid, and potentially dangerous, increase in water height.
The impounding, the extraction, the creation of barriers and the rapidly changing river heights and flows all impact on fish feeding and migration patterns. The demand for a supply of potable water has resulted in an evident change to many of our river and loch systems too, although some have been very beneficial. For example the lochs of the Trossachs - the main source of Glasgow's drinking water - are very attractive and productive fisheries. Others have been less so where streams, prime areas for reproduction of fish, have been disrupted. Rivers have been channelled for road systems, dammed for industrial purposes and retained to lessen their impact on agricultural land. The canalisation of the rivers has made them prone to flooding, especially where flood plains have been drained and embanked.
Our attempts to improve salmon 'lies' may actually have resulted in damage. The 'croys' placed in rivers to make streams and pools more attractive to fish only do so for a few seasons, then their effectiveness fades. There are several layers of flow in rivers, which may help to explain this. There are surface currents and deeper currents of mid water, both of which are quite different from the surface layers. Deeper still, there are the bottom currents, which are slower as they drag along the roughness of river bed - they are extremely powerful. Finally there is the flow of silt, gravel and stones, which constantly sculpts the bed of the river into new shapes. Most fish like to adopt lies, which provide them with a supply of foodstuffs, adequate cover, if they have to hide, and a comfortable and even flow. To place obstructions in the path of flow, such as croys, often gives rise to turbulence. Therefore, it is evident that man's intervention tends to be 'against the grain' of the river, and having negative as well as positive consequences. It is the sheer variety of Scotland's landscape - and her fishing opportunities - which attract people to the remoter parts of the country. Within a few miles, it is possible to fish for wild trout in the lochs of the 'machair', the coastal fringe of sand-dunes where the lochs are rich and productive, yet so close to the waves of the ocean; to fish in dark, peaty lochs amongst heather moors; to fish in one of the great lochs contained between high rocky peaks then fish for 'wee brownies' in a tumbling burn. What a wonderful, endless variety of fishing.