Appendix 4: Nature-based solutions for water resources glossary
Published 17 August 2026
Applies to England
© Crown copyright 2026
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Glossary of terms
Beaver dams – Beaver dams are natural barriers built by beavers across a stream or river, constructed from tree branches, mud, rocks and vegetation to block the flow of water and create a deep, still pond.
Berms – A berm is a level space, shelf, or raised barrier (usually made of compacted soil) separating areas in a vertical way, especially partway up a long slope.
Broadleaved woodland – A broadleaved woodland is a forest ecosystem dominated by deciduous trees with broad, flat leaves (for example, oak, beech, birch) rather than needles.
Bunds – Bunds are raised earthen walls, levees or dams used to control water flow, retain moisture in fields, or prevent flooding.
Fluvial floodplain – A fluvial floodplain is a relatively flat, low-lying area of land adjacent to a river or stream channel that is formed by the deposition of sediment (alluvium) during floods. It acts as a natural storage area for excess water when high flow exceeds the river’s capacity, commonly extending from the banks to the valley base.
Offline storage features – An offline water storage feature is a natural or engineered basin (such as a pond or a wetland) designed to temporarily hold excess water, typically from a river, stream or heavy rain, completely detached from the main water channel.
Riparian corridor – A riparian zone or corridor is the interface between land and a river or stream. Riparian zones are transitional areas between terrestrial and aquatic ecosystems that play a critical role in regulating hydrological processes, maintaining water quality and supporting biodiversity.
Runoff attenuation features (RAFs) – RAFs are a landscape intervention that intercepts and attenuates a hydrological flow pathway to provide multiple benefits, including flood management and improving water quality. The design philosophy is to create features that slow, store and filter runoff in the rural landscape. Examples include retention basins, swales and permeable surfaces.
Runoff infiltration split – Runoff-infiltration split (or partitioning) is the hydrologic process that determines how precipitation is divided at the land surface between water that infiltrates the soil (seeps into the ground) and water that becomes surface runoff (flows over the land). This partitioning is fundamental to controlling flooding, groundwater recharge, and soil moisture availability.
Swales – Swales are low-lying, often damp stretches of land or shallow drainage channels with gently sloping sides.