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Afon Caerfanell and waterfall
Under Cerrig Edmwnt, Talybont.
This river is a right-bank tributary of the River Usk of whose source is in the eastern end of the Brecon Beacons national park in South Wales, and joins the main river further downstream of Brecon.
The catchment area is 32.4 km2 and is an area of high precipitation, with 1800- 2000mm/year on average falling near the source and 1100mm/year near the confluence with the Usk. The valley of the Caerfanell lies within the Brecon Beacons national park and is relatively untouched except in more recent years where the river has attracted many holiday homes to situate nearby having an impact on surface runoff. The surrounding forest trees are coniferous and mostly evergreen, which also have an impact on runoff through interception and evapo-transpiration. A reservoir (the Talybont reservoir) was built in 1937 to store water, and now is being used as a drinking water supply for surrounding areas. The river has a built a delta, where it enters the reservoir, and just above the delta, the river has a strong tendency to meander eroding the farmland either side, although the farmer has attempted several times to straighten the river to protect his livestock.
The Caerfanell valley has been carved into sedimentary rocks of the Devonian age (about 360 million years ago). These are known as the old red sandstone, which consists of a thick sequence of relatively resistant sandstones with easily friable and erodable mudstones. Also the acidity of water caused by the coniferous trees helps erode the mudstone. This modification of the sand and mudstones has made a series of attractive waterfalls in areas such as Blaen y Glynn.
During the Pleistocene there was an ice cap on the Brecon Beacons with valley glaciers descending from it along the Caerfanell. The ice left behind glacial troughs (steep sided U-shaped valleys).
Within the ten thousand years since the ice melted, the Caerfanell and its tributaries have begun to alter the glacial landscape, creating in places steep v-shaped valleys and re-worked glacial deposits with some sediments still carrying its glacial origin.
Afon Caerfanell and waterfall
Under Cerrig Edmwnt, Talybont.
This river is a right-bank tributary of the River Usk of whose source is in the eastern end of the Brecon Beacons national park in South Wales, and joins the main river further downstream of Brecon.
The catchment area is 32.4 km2 and is an area of high precipitation, with 1800- 2000mm/year on average falling near the source and 1100mm/year near the confluence with the Usk. The valley of the Caerfanell lies within the Brecon Beacons national park and is relatively untouched except in more recent years where the river has attracted many holiday homes to situate nearby having an impact on surface runoff. The surrounding forest trees are coniferous and mostly evergreen, which also have an impact on runoff through interception and evapo-transpiration. A reservoir (the Talybont reservoir) was built in 1937 to store water, and now is being used as a drinking water supply for surrounding areas. The river has a built a delta, where it enters the reservoir, and just above the delta, the river has a strong tendency to meander eroding the farmland either side, although the farmer has attempted several times to straighten the river to protect his livestock.
The Caerfanell valley has been carved into sedimentary rocks of the Devonian age (about 360 million years ago). These are known as the old red sandstone, which consists of a thick sequence of relatively resistant sandstones with easily friable and erodable mudstones. Also the acidity of water caused by the coniferous trees helps erode the mudstone. This modification of the sand and mudstones has made a series of attractive waterfalls in areas such as Blaen y Glynn.
During the Pleistocene there was an ice cap on the Brecon Beacons with valley glaciers descending from it along the Caerfanell. The ice left behind glacial troughs (steep sided U-shaped valleys).
Within the ten thousand years since the ice melted, the Caerfanell and its tributaries have begun to alter the glacial landscape, creating in places steep v-shaped valleys and re-worked glacial deposits with some sediments still carrying its glacial origin.