Land drainage can help reduce flood risk

8Jan2016

Recent events have highlighted the UK’s vulnerability to extreme weather and increased risk of flooding. There has been widespread comment on the role of farmers and the management of agricultural land in both increasing severity of floods and managing flood risk. There is good evidence that well designed and maintained land drainage systems have a significant role in reducing floods.

Many aspects of rural land management impact on flood risk, including the benefits of woodland in upper catchments intercepting rainfall and slowing the flow, and flood alleviation schemes where agricultural land in lower catchments is allowed to flood to protect urban areas. ADAS Land drainage national specialist Kirk Hill said “An often forgotten point is the importance of agricultural field drainage in the management of flood risk, where flood risk can be reduced and land can remain in agricultural production to produce food and fuel.”

Good field drainage and soil management reduces the susceptibility of soils to waterlogging and decreases the volume and rate of surface runoff. It works the same way that we are trying to imitate with modern Sustainable Urban Drainage Systems (SuDS). It removes excess soil water over a period of days leaving the soil able to absorb rainfall more readily when the next storm arrives.

Field drainage needs to be considered as a whole, involving soil condition, design and maintenance of piped drainage systems and ditch and watercourse networks. Poorly designed and maintained drainage can increase flood risk so it is important to do things properly, but in general good agricultural drainage should not only help reduce flood risk but also reduce soil erosion, leading to silting up of water courses and improve river water quality.

“Well managed soils are vital for environmental protection, agricultural production and sustainable farm business and land drainage is key to all of this” said Kirk Hill. ADAS has a wealth of knowledge of the current state of the UK land drainage infrastructure indicating a considerable proportion of the drained area pre-dates modern design standards, and poor maintenance of outfalls and changes in sub-soiling practice may have contributed to a reduction in the efficiency of secondary drainage on impermeable soils.

Kirk commented that after many years of decline there is a resurgence of interest in land drainage and he is speaking at AHDB events about the benefits of drainage during February at Kent, Northamptonshire and Lincolnshire.

 Further Information Contact Kirk Hill kirk.hill@adas.co.uk 01432 821026 or 07831 752874  

From ADAS