Ditches

How

Over time, drainage channels undergo natural succession from recently cleaned to ditches that have become choked with silt and vegetation. Each phase has its characteristic wildlife. Try to maintain a variety of ditch habitats around the farm by cleaning ditches on a rotation.

To make the best decisions on how to manage your ditches, it is important to know how wildlife is currently making use of them. Ditch clearance is usually best undertaken in the autumn and winter months, as this will limit the impact on wildlife. The frequency of clearance will depend on the drainage function and the speed with which the ditch silts up.

It is generally best to not clear entire ditch lengths in a single year, and instead manage them on a rotation to allow wildlife to re-colonise newly cleared areas quickly. In large drainage systems, a range of dredging rotations may be appropriate. The most important drainage channels could be dredged on a more regular basis than those that have less of a drainage function. Managing alternate halves in wide ditches each time within a rotation allows rapid re-colonisation of the excavated area. For some species however, this partial clearance is not appropriate. It is important to look at the species using the ditches before making management decisions. Consult an expert for advice if you are unsure how to proceed.

Weed cutting buckets enable excessive vegetation to be removed while retaining many aquatic plants, so that the gap between full clearance operations can be extended.

It is important to avoid steepening ditch slopes while clearing vegetation. A slope angle of 30-40^o is ideal. Avoiding the disturbance of any shallow shelves which can be valuable for freshwater invertebrates is very important. If significant bank works are being undertaken, consider including a range of slope angles. Plenty of shallow slopes on south-facing banks should be included where possible, to maximise wildlife value.

Ditch bank vegetation should ideally be managed on a rotation of 2-5 years, with no more than half of the ditches managed in any one year. Try to restrict cutting of bank vegetation to the autumn and winter months and where possible, alternate cuts along short sections to create a varied age structure of vegetation along the length of a ditch.

Ditches are not isolated features, so consideration should be given to surrounding features when developing management plans. Maintaining existing margins and/or extending buffer strips to at least 6m will not only enhance connectivity to the wider landscape, but will also help to stabilise ditch banks and protect the watercourse from pollution from farm inputs and run–off.

Open and sunny ditches are often the most wildlife-rich so avoid planting new hedges or trees too close to them, particularly on the southern side, as shading will impact on their value. However, allowing isolated trees or patches of scrub to develop in discrete areas can add some habitat variety locally.

Leaving piles of cut vegetation, including reeds or grass clippings from your ditch management can provide important egg laying heaps for grass snakes. A lack of quality egg-laying sites can limit the success of grass snakes, and the heat of the decomposing vegetation incubates the eggs.

It is important to be aware of invasive species in ditches, which if left unchecked can choke out native vegetation and significantly reduce their wildlife value.