The River Bleng is one of the more remote rivers of the western fells. It is born in a remarkable amphitheatre created by the steep sides of Caw Fell, Haycock and Seatallan. Although it soon flows out of the high ground, it remains an attractive river for most of its course, running through a steep sided valley from Blengdale Forest to Gosforth (the steepest section of the river comes just after it enters the forest, as does the only waterfall). This is the only part of the river accessible by car – the road from Gosforth to Santon Bridge actually crosses it twice as the river curves around to flow back into the Irt.
The River Bleng rises on the western slopes of Haycock.
The Bleng flows west from its source into Blengdale Forest, then turns south-west and almost reaches Gosforth, before turning east to run into the River Irt.