Fieldwork in Snowdonia

Studying the River Conwy

"How natural is your chosen stretch of river?" - that is the question. So off to Migneint Moor in the Snowdonia National Park to find the answer. The renewal of cattle grids prevented the coach from going any further that Ysbyty Ifan, the highest village on the river, so a system of mini-bus shuttles had to be set up to travel further up the river. Firstly, however, measurements such as width, depth, wetted perimeter and sediment size and roundness were taken.  

The village has been prone to flooding. The ancient bridge interrupts the flow of the river and sediment has built-up on the upstream side, restricting the river channel.  In the photo (LH) a small wall can be seen protecting the cottages. In the photo above, the coach is standing on top of the flood defence bank built in the early 1990's. Here then, the river has been managed to help reduce the risk of flooding.

Up onto Migneint Moor, where although there are no settlements, the land is used for rough grazing of sheep. This will have altered the hydrology of the area by removing scrub vegetation and replacing it with peat bogs and rushes. In the past, this area was heavily glaciated, creating a flat bottomed valley which subsequently was filled with sludgy material as the ice melted - solifluction. This resulted in a flat floor to the valley which has encouraged the formation of meanders, a feature more usually found in the lower course of a river.

Finally on to one of the tributaries of the Conwy, Nant-y-brwyn. A classic V-shaped valley with outcrops of slate. the stream tumbles through a series of pools and riffles. Although the water looks like it is flowing quickly, the friction from the boulders slows it down.

Here the features might be natural but the land itself has been altered heavily by farming. The impermeable rocks and saturated peat result in faster rates of runoff, which in turn lead to flooding further downstream - a problem the town of Llanrwst knows only too well.