The lower Stort
The lower Stort, upstream of the confluence with the Lea, has been made navigable by turning the original river into a canal (the ‘Navigation’). This allows boats to travel for 12 miles up to Bishop's Stortford. Historically, horse-drawn barges were used to transport timber and coal upstream, and grain and malted barley downstream to London.
Along this stretch the valley is characterised by wide flood plains, crossed by ditches and backwater streams. By far the greater part of this floodplain is pasture, used either for grazing or haymaking. Fortunately, there has been very little gravel extraction or other invasive industry.
Also in this stretch are several notable wetland nature reserves, including Hunsdon Mead, Parndon Moat Mead, May Meads Marsh, Sawbridgeworth Marsh, Thorley Wash and Rushy Mead. These reserves protect improtant areas of sedge, reedbeds, carr and wet grassland, and are characteristic of what much of the Stort Valley was like before the construction of the Navigation.
Large areas of this bottom section of the Stort experience regular flooding, particularly during the winter, and this attracts a wide range of waterbirds and waders on their autumn and spring migrations.
The Navigation channel itself is relatively poor habitat, having been subject to dredging and heavy overshading for many areas. The towpath is heavily used by the public, and the river experiences heavy boat traffic, with the associated disturbance to wildlife.
One of the main features of the lower Stort is the preservation of the Old River Stort in the form of backwater loops and meanders which were cut off when the canal was dug. These preserve the original character of the river and in many cases have picturesque gravel riffles and deeper pools. The backwaters are also home to some rare species, and typically form sanctuary areas for wildlife away from the busy Navigation.
Several brooks flow into this part of the Valley. On the east there is the Canons Brook, the Pincey Brook, the Little Hallingbury Brook and the Great Hallingbury Brook. These frequently bring with them excessive surface water run-off, plastic rubbish, nutrient rich water from sewage works and polluting run-off from agricultural land. The Great Hallingbury Brook in particular carries the treated effluent from the Bishops Stortford Treatment Works and contributes a large volume to the river flow on a daily basis.
On the west side of the valley there are the Eastwick Brook, Fiddlers Brook, Sawbridgeworth Brook and the Spell Brook. These drain mostly agricultural land but increasingly are subject to urban run-off, with its associated problems.
The upper Stort
At Bishop's Stortford the Navigation ceases, and for a short while we find the original River Stort in its channel. In a number of places there are characteristic gravel bed and riffles, with good water quality which supports trout.
The geology here has changed from boulder clay and gravel to chalk, and with this we find winterbourne streams and springs rising in the bed of the river.
Above Manuden the river is essentially a winterbourne stream, running only in times of high rainfall. The land here is predominantly arable with cultivation taking place right the way down to the river channel. At Clavering the river reappears in the form of a pleasant brook, and continues to wind its way through fields towards Nuthampstead, via villages such as Starlings Green, Langley Lower Green and Further Ford End. The source of the Stort is located in a lake some 10 miles away from Bishop's Stortford.