SuDS and glory

With the need to implement sustainable drainage systems (SuDS) soon to be a legal requirement in England, ACO has produced a guide covering the principles of sustainable drainage.

By replicating nature, SuDS can lower the impact of surface water flooding, improve water quality and protect biodiversity. This is achieved by collecting, cleaning, holding, releasing and reusing rainfall.

In Scotland, SuDS are already a legal requirement for all developments (except single dwellings that drain to the water environment unless they discharge to coastal waters). In Wales, new developments of more than one single dwelling house or where the construction area is 100 sqm or more require SuDS for surface water. In England, SuDS have not been mandatory for planning applications, despite being recommended for major developments (ten or more homes or on areas greater than 0.5 hectares). In January 2023, however, the government announced its plans to implement Schedule 3 in England. This means that all new developments will be legally required to integrate SuDS.

Housebuilders and developers in England have found themselves on the back foot. SuDS were first included as part of Schedule 3 in the Flood and Water Management Act passed in April 2010. It was thought that better planning would be sufficient in most circumstances, which led to some confusion. In making Schedule 3 mandatory, it removes the automatic right to connect to public sewers – instead, you will be required to satisfy the SuDS Approving Body (SAB) first. These approving bodies then determine if the drainage proposal adheres to a technical national standard produced by the Department for Environment, Food and Rural Affairs. Schedule 3 is not limited to new developments either; it also applies to renovation work that involves multiple dwellings or projects of more than 100 sqm.

SuDS options

• Vegetation – strips and swales to filter and control the water’s flow
• Permeable structures – filter drains, green roofs and bioretention areas that allow water to percolate in an area for cleaning, storage and controlled release  
• Infiltration devices – features that allow soakage into the ground 
• Open depressions – basins, ponds and wetlands that collect, clean and store water naturally while also providing amenity and support for local wildlife; and
• Engineered structures – geocellular boxes, tanks, oversized pipes, proprietary water treatment systems and flow controllers.

Working with nature

Around 5.2 million properties in England are currently at risk of flooding, according to the Environment Agency. SuDS lower the risk of flooding and erosion by controlling flow and frequency of surface water runoff. On developments where SuDS are not in place, rain from roofs, roads and other hard surfaces collects into gullies, channels and pipes before being released into the local river network or sewer system. This not only worsens the impact of heavy rainfall, but also allows silts, oils and other pollutants to spread before they can be trapped, removed or broken down naturally. This means wetlands, watercourses and other habitats are harmed. SuDS not only manage the flooding and pollution aspects of drainage, but they also ensure that community and wildlife are considered.

Implementing SuDS: Practical advice, key information and preparing developments for Schedule 3 covers: how to implement SuDS, based on the CIRIA SuDS Manual (C753); their applications in a variety of developments; different techniques that can be applied, including nature-based solutions; and ‘hard’ engineered systems that can help meet biodiversity net gain (see SuDS options). It will help housebuilders and property developers not only meet their SuDS responsibilities, but feel confident in doing so.

Download ACO’s free SuDS implementation guide at bit.ly/ACO_SuDSguide

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