Ensure that mitigation measures are included where culverting is unavoidable. SEPA guidance on culverting and best practice should be taken into consideration when developing proposals. The best ditches for wildlife generally have gently sloping banks, and contain both aquatic and emergent plants. Marshy grassland alongside a ditch increases its diversity and wildlife value. A careful balance must always be maintained to ensure that the hydraulic capacity of ditches is not adversely affected in any way, as the primary safety objective of the drainage system is to avoid ponding on road surfaces.
Most drainage systems can, however, serve biodiversity as well as safety objectives.
Settlement lagoons and other pollution control features can provide opportunities for enhancing wildlife value. For example, shallow areas can be planted with native wetland plants which support a variety of invertebrates and other species. Road spills following accidents can result in pollution of adjacent watercourses. Their places of shelter are protected by legislation All year Where known to use ditches, seek to manage vegetation to provide suitable conditions. An Inventory of Wildlife Mitigation Measures DMRB Vol.