Drainage Ditches
With their characteristic straight lines and right angles, the geometry of drainage ditches provides stark contrast to the more sinuous network of streams and rivers that blanket our countryside. Yet, there are over half a million kilometres of manmade ditches in the UK, delving even deeper into the landscape than their natural counterparts. What’s more, their great number makes them a hugely important resource for local wildlife.
What Are They? Drainage ditches are manmade water bodies that exist to manage the flow of water entering or leaving an area of land in a controlled fashion (very often, by lowering the water table and removing excess as quickly as possible). They can cover just a few fields or, as an in the case of the Weald Moors, an entire landscape, enabling much greater flexibility in what farming practices can take place and where.
Ditches that regularly contain standing or flowing water can support an array of aquatic and semi-aquatic plants and insects. However, the type of wildlife you may find in any particular channel will invariably dictated by the way it is looked after. Clear water, a variety of plant life and an abundance of insects are all signs of good ditch management and where they are present, numerous feeding and nesting habitat will be created for birds. Yellow Wagtail, Song Thrush, Starling, Reed Bunting and Lapwing all feed here, while Barn Owl will hunt along watercourses fringed by strips of marginal vegetation that harbour voles and other small mammals, for whom this is also an important habitat.
What To Look For: Drainage ditches come in an assortment of different shapes and sizes. On the Weald Moors, some of the most apparent are the open perimeter drains found at practically every field edge. Discharging into them, there may also be another invisible network of sub-surface drains, removing water from the soil below ground. While their number and extent are usually dictated by local conditions, outfall pipes in perimeter ditch walls and vigorous crop or grass growth on the soil directly above them can provide a clue to the existence of subterranean infield drains.
Above ground, drainage channels with shallow profiles are generally the best places to begin a ditch safari because they provide the best conditions for invertebrate life to thrive. However, steep-sided ditches can have great value, too, and are favoured by Water Voles, which build entrances to their extensive burrow systems above and below the water line. As we’ve already seen, good drains have plenty of aquatic and bankside vegetation. Those supporting the highest numbers of insects will be the ones where marginal and submerged plants are cleared a little and often (preferably in autumn and typically along one side of a watercourse or, perhaps, the middle third of its width). Such an approach helps ensure foliage is ever present for species that need it but also favours those that require clear water and bare ground to complete their life cycles.
On the Weald Moors: Drainage ditches have been part of Weald Moors life for at least half a millennia, ranging from the imprecise and haphazard to landscape defining in their extent. However, what these historic developments do have in common is their contribution to the vast shrinkage of peatland on the moors. So much so that the area’s claims to wetland status are, for the most part, really a matter of heritage rather than reality. Water movement within peat soil is a very slow process, limiting the influence of individual ditches to perhaps the five or ten metres of land adjacent to them. In order to drain the whole area, this has left the moorlands with a vast, varied and highly complex system of active and relic manmade channels, all directing water westwards into the River Tern.
For the avid drainage ditch wildlife watcher, there is much to see. On Crudgington Drive, you’ll find a range of deep and shallow perimeter ditches along the field edge and roadside. Some have long since dried out but others are so seasonally inundated they regularly pour water across the flooded landscape, creating temporary hotspots for overwintering birds. Some of the deepest channels spiriting water away from the moors are those along Kynnersley Drive, which offer good summer views of the area’s dragonflies and damselflies. Typically, Wall Farm is probably the best place to see local ditch management for wildlife at its best and it’s fair to say you could find just about any of the Weald Moors wetland related species here.