Swales - Overview

Swales are shallow vegetated open channels. They can be natural, but within a developed environment they’re usually designed as part of an engineered SuDS scheme. Typically featuring a wide-bottomed trapezoidal or parabolic cross-sectional profile for ease of maintenance and construction, the design also offers good hydraulic performance when combined with engineered SuDS systems.

During extreme rainwater events and/or where a proposed swale follows a steep gradient, berms, check dams or weirs may be incorporated within the swale channel. The flow velocity is reduced, whilst the discrete ‘bays’ that are created within a swale, may be used to capture and retain accidental pollution spills to a localised area of the system. Allowing simple identification of accidental spills, facilitating its clean-up and minimising any resultant remedial work that may be required. Slowing the travel of water in this way also allows the swale to store and attenuate the water at a preferred rate.