© Nanda Sluijsmans (Licensed under CC BY-SA 2.0). Kindly recommended by UKCEH.
The following is a short summary of the habitat type and how to create/enhance it to a "good" condition. For an informed position, please refer to official up-to-date UKHAB documentation or the UK Government's Condition Assessment Sheet.
Synonyms: Balancing Pond, Bio-Retention Strips
Description: A swale, in the context of sustainable drainage, is a shallow channel designed to store and convey surface water runoff. Consists of vegetated and gently sloped features designed to manage water runoff, filter pollutants and increase rainwater infiltration. May include gravel layers, perforated under-drains and overflow drains (Source: Natural England).
If you wish to select this habitat on a habitat selection screen, it can be found under Urban (see guide).
Swales are often damp, particularly in the lowest part, but have a range of soil conditions, which mean that they can support a high diversity of plants. The vegetation in a swale is often lightly managed, with plants being allowed to grow tall and provide visual interest. Plants should be selected that can withstand periods of drought. With most low-maintenance swales, it is advisable to establish vegetation by seeding with a variety of native species, including wetland, wet grassland, and dry grassland mixtures, chosen according to the local setting and conditions and predictions of how often the swale will convey water (Source: Natural England).
If the gradient is suitable, swales may include stop logs or check-dams designed to slow the flow. Inlets and outlets and other places that are subjected to high flow rates, that could cause erosion, may need to be armoured. On permeable ground, where the underlying geology is suitable, water may also infiltrate. A swale can also remove pollutants. This may be valuable where water is to be discharged into a natural waterbody. Adequate space should be made available to ensure that bioremediation objectives are met. (Source: Natural England).
Assessment Questions
Is the feature specifically constructed to manage water runoff?
Does it have a gentle slope and is it vegetated?
Is it designed to filter pollutants and increase rainwater infiltration?
Is it integrated into an urban or built environment?
If YES, then it is likely 'Urban - Bioswale'
How to Create / Enhance to a "Good" condition
How to create
How to get a "moderate" rating
In a management plan aiming to achieve ‘moderate’ condition, at least three of the following will be true:
Vegetation structure will be varied, providing opportunities for vertebrates and invertebrates to live, eat and breed. A single structural habitat component or vegetation type does not account for more than 80% of the total habitat area.
The habitat parcel will contain different plant species that benefit wildlife. For example, flowering species provide nectar sources for a range of invertebrates at different times of year.
Invasive non-native plant species (as listed on Schedule 9 of WCA1) and others which are to the detriment of native wildlife will cover less than 5% of the total vegetated area.
A variety of flower species suited to wetland or riparian situations will be planted.
The seed mix will be mostly native species. Where non-native plant species are present, they will not be harmful to wildlife. The planting mix will exclude invasive non-native species (INNS).
Source: Natural England
How to get a "good rating"
In a management plan aiming to achieve ‘good’ condition, all of the following will be true:
Vegetation structure will be varied, providing opportunities for vertebrates and invertebrates to live, eat and breed. A single structural habitat component or vegetation type does not account for more than 80% of the total habitat area.
The habitat parcel will contain different plant species that benefit wildlife. For example, flowering species provide nectar sources for a range of invertebrates at different times of year.
Invasive non-native plant species (as listed on Schedule 9 of WCA1) and others which are to the detriment of native wildlife will cover 0% of the total vegetated area.
A variety of flower species suited to wetland or riparian situations will be planted.
The seed mix will be mostly native species. Where non-native plant species are present, they will not be harmful to wildlife. The planting mix will exclude invasive non-native species (INNS).
Source: Natural England
Useful Resources
Guide 2 - Bioretention areas
Please note that this is a simple guide to help identify the habitat. For a definitive description, please refer to UKHab documentation. Joe's Blooms takes no responsibility for the content of external links.