Distance: 20.8 miles
The 21-mile New Bedford River is a man-made by-pass of the River Great Ouse at the Fens in Cambridgeshire. It is a tidal stretch of river.
You may also know it as the Hundred Foot Drain. This is because of the distance between the tops of the two embankments on either side of the river, The river is fairly straight for much of its length.
It provides an almost straight channel between Earith and Denver Sluices. It is tidal, with reverse tidal flow being clearly visible at Welney, some 19 miles (31 km) from the sea.