Vegetation cutting – vegetation such as brambles grow up annually and require active control and cutting back. While they have some wildlife value they can quickly overwhelm a ditch and block it. Other vegetation will also grow up on the banks which may also need cutting. Vegetation helps Water Voles as they need cover to protect them from predators which might eat them in which case a regime can be devised that relies on cutting each bank separately in alternate years. Different heights of cut take into account flood risk. This technique retains vegetation cover for invertebrates and helps to stabilise the banks.
Silt removal – this may be necessary every 3-4 years to ensure that the channels are clear and that they can hold a large amount of water. This should be carried out in the winter months and ideally any silt removed from the site to prevent the collapse of the bank compaction or damage, and thus remove dominating plants such as nettle, dock and thistle growth. If it cannot be removed it should be placed at least 3 metres away from the banks’ edge.
Bank stabilisation – well vegetated banks hold the soil together and helps to stop them
collapsing. This stabilises the channel during fast water fl ow and thus helps to prevent
undercutting and slumping of the banks. Therefore vegetation cutting should not involve low strimming or removal of the ground cover.
Bank profile – The best angle for the bank profi le of a ditch is between 45° – 90° for Water Voles. This ensures the bank is not too steep so that water voles can use the whole width but is also not too shallow to allow them to make their burrows. A high bank with some stepping in it also ensures that water voles survive fl ooding events as it enables them to have higher ground available that they can retreat to. A wide high bank with a gentle slope is ideal for colonisation by different vegetation groups and this offers an opportunity for a variety of plant and invertebrate species.
Blockage removal – this should be carried out frequently to ensure the channel is able to carry water away and flooding does not occur. Blockages that cause flooding will threaten Water Voles which may drown in their burrows or be displaced, putting them at increased risk of predation. Sometimes storing the water and allowing it to seep into the ground where possible has wider benefits.
Rubbish and garden debris – should not be put into ditches, even when dry as this encourages rats, causes pollution and prevents the flow of water. Blockages in the network as a result of poor management can be felt in other areas which then flood and lead to high water levels.
Water – ditches are most useful for wildlife when they are holding water. Dry ditches can be used by some mammals and reptiles but Water Voles need waterways to contain water as they are a key feature of their escape strategy from their many predators. However, Water Voles do not want to live on sites that are fluctuating, that have flooding and drought events both of which put their survival at risk. A drainage ditch with a constant, year round supply of water in it has most wildlife value.
This can be achieved by putting in a bund that holds the water back once it reaches a certain low level. This will not hinder water flow during high rain events or cause flooding but it should not be done in a rife where it could impede the passage of fish.
Vegetation margin at the top of the bank – Leaving a large margin of vegetation at the top of the bank is helpful as Water Voles, butterflies, damsel- and dragonflies as well as wetland birds will use this area for food and shelter. Also, buffers between farmland and water courses are important in tackling diffuse pollution via run-off from fields by acting as a barrier to pesticides, fertilizers and silt entering the water. The can thus help improve water quality for the benefit of all wildlife.← Ditches are better than culverts Contents Habitats: Plants and Animals →